2196 lines
86 KiB
Plaintext
2196 lines
86 KiB
Plaintext
What's New in Python 2.2a3?
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===========================
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Core
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Library
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Tools
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Build
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New platforms
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Tests
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Windows
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+ The w9xpopen hack is now used on Windows NT and 2000 too when COMPSPEC
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points to command.com (patch from Brian Quinlan).
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What's New in Python 2.2a2?
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===========================
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Build
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- Tim Peters developed a brand new Windows installer using Wise 8.1,
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generously donated to us by Wise Solutions.
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- configure supports a new option --enable-unicode, with the values
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ucs2 and ucs4 (new in 2.2a1). With --disable-unicode, the Unicode
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type and supporting code is completely removed from the interpreter.
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- A new configure option --enable-framework builds a Mac OS X framework,
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which "make frameworkinstall" will install. This provides a starting
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point for more mac-like functionality, join pythonmac-sig@python.org
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if you are interested in helping.
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- The NeXT platform is no longer supported.
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- The `new' module is now statically linked.
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Tools
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- The new Tools/scripts/cleanfuture.py can be used to automatically
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edit out obsolete future statements from Python source code. See
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the module docstring for details.
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Tests
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- regrtest.py now knows which tests are expected to be skipped on some
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platforms, allowing to give clearer test result output. regrtest
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also has optional --use/-u switch to run normally disabled tests
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which require network access or consume significant disk resources.
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- Several new tests in the standard test suite, with special thanks to
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Nick Mathewson.
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Core
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- The floor division operator // has been added as outlined in PEP
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238. The / operator still provides classic division (and will until
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Python 3.0) unless "from __future__ import division" is included, in
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which case the / operator will provide true division. The operator
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module provides truediv() and floordiv() functions. Augmented
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assignment variants are included, as are the equivalent overloadable
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methods and C API methods. See the PEP for a full discussion:
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<http://python.sf.net/peps/pep-0238.html>
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- Future statements are now effective in simulated interactive shells
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(like IDLE). This should "just work" by magic, but read Michael
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Hudson's "Future statements in simulated shells" PEP 264 for full
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details: <http://python.sf.net/peps/pep-0264.html>.
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- The type/class unification (PEP 252-253) was integrated into the
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trunk and is not so tentative any more (the exact specification of
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some features is still tentative). A lot of work has done on fixing
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bugs and adding robustness and features (performance still has to
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come a long way).
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- Warnings about a mismatch in the Python API during extension import
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now use the Python warning framework (which makes it possible to
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write filters for these warnings).
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- A function's __dict__ (aka func_dict) will now always be a
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dictionary. It used to be possible to delete it or set it to None,
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but now both actions raise TypeErrors. It is still legal to set it
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to a dictionary object. Getting func.__dict__ before any attributes
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have been assigned now returns an empty dictionary instead of None.
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Library
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- New class Differ and new functions ndiff() and restore() in difflib.py.
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These package the algorithms used by the popular Tools/scripts/ndiff.py,
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for programmatic reuse.
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- New function xml.sax.saxutils.quoteattr(): Quote an XML attribute
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value using the minimal quoting required for the value; more
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reliable than using xml.sax.saxutils.escape() for attribute values.
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- Readline completion support for cmd.Cmd was added.
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- Calling os.tempnam() or os.tmpnam() generate RuntimeWarnings.
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- Added function threading.BoundedSemaphore()
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- Added Ka-Ping Yee's cgitb.py module.
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- The `new' module now exposes the CO_xxx flags.
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New platforms
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C API
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- Two new APIs PyOS_snprintf() and PyOS_vsnprintf() were added
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which provide a cross-platform implementations for the
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relatively new snprintf()/vsnprintf() C lib APIs. In contrast to
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the standard sprintf() and vsprintf() C lib APIs, these versions
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apply bounds checking on the used buffer which enhances protection
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against buffer overruns.
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- Unicode APIs now use name mangling to assure that mixing interpreters
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and extensions using different Unicode widths is rendered next to
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impossible. Trying to import an incompatible Unicode-aware extension
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will result in an ImportError. Unicode extensions writers must make
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sure to check the Unicode width compatibility in their extensions by
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using at least one of the mangled Unicode APIs in the extension.
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- Two new flags METH_NOARGS and METH_O are available in method definition
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tables to simplify implementation of methods with no arguments and a
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single untyped argument. Calling such methods is more efficient than
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calling corresponding METH_VARARGS methods. METH_OLDARGS is now
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deprecated.
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Windows
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- "import module" now compiles module.pyw if it exists and nothing else
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relevant is found.
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What's New in Python 2.2a1?
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===========================
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Core
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- TENTATIVELY, a large amount of code implementing much of what's
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described in PEP 252 (Making Types Look More Like Classes) and PEP
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253 (Subtyping Built-in Types) was added. This will be released
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with Python 2.2a1. Documentation will be provided separately
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through http://www.python.org/2.2/. The purpose of releasing this
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with Python 2.2a1 is to test backwards compatibility. It is
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possible, though not likely, that a decision is made not to release
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this code as part of 2.2 final, if any serious backwards
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incompapatibilities are found during alpha testing that cannot be
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repaired.
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- Generators were added; this is a new way to create an iterator (see
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below) using what looks like a simple function containing one or
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more 'yield' statements. See PEP 255. Since this adds a new
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keyword to the language, this feature must be enabled by including a
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future statement: "from __future__ import generators" (see PEP 236).
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Generators will become a standard feature in a future release
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(probably 2.3). Without this future statement, 'yield' remains an
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ordinary identifier, but a warning is issued each time it is used.
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(These warnings currently don't conform to the warnings framework of
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PEP 230; we intend to fix this in 2.2a2.)
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- The UTF-16 codec was modified to be more RFC compliant. It will now
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only remove BOM characters at the start of the string and then
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only if running in native mode (UTF-16-LE and -BE won't remove a
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leading BMO character).
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- Strings now have a new method .decode() to complement the already
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existing .encode() method. These two methods provide direct access
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to the corresponding decoders and encoders of the registered codecs.
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To enhance the usability of the .encode() method, the special
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casing of Unicode object return values was dropped (Unicode objects
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were auto-magically converted to string using the default encoding).
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Both methods will now return whatever the codec in charge of the
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requested encoding returns as object, e.g. Unicode codecs will
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return Unicode objects when decoding is requested ("<22><><EFBFBD>".decode("latin-1")
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will return u"<22><><EFBFBD>"). This enables codec writer to create codecs
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for various simple to use conversions.
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New codecs were added to demonstrate these new features (the .encode()
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and .decode() columns indicate the type of the returned objects):
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Name | .encode() | .decode() | Description
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----------------------------------------------------------------------
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uu | string | string | UU codec (e.g. for email)
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base64 | string | string | base64 codec
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quopri | string | string | quoted-printable codec
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zlib | string | string | zlib compression
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hex | string | string | 2-byte hex codec
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rot-13 | string | Unicode | ROT-13 Unicode charmap codec
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- Some operating systems now support the concept of a default Unicode
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encoding for file system operations. Notably, Windows supports 'mbcs'
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as the default. The Macintosh will also adopt this concept in the medium
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term, although the default encoding for that platform will be other than
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'mbcs'.
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On operating system that support non-ASCII filenames, it is common for
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functions that return filenames (such as os.listdir()) to return Python
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string objects pre-encoded using the default file system encoding for
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the platform. As this encoding is likely to be different from Python's
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default encoding, converting this name to a Unicode object before passing
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it back to the Operating System would result in a Unicode error, as Python
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would attempt to use its default encoding (generally ASCII) rather than
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the default encoding for the file system.
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In general, this change simply removes surprises when working with
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Unicode and the file system, making these operations work as you expect,
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increasing the transparency of Unicode objects in this context.
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See [????] for more details, including examples.
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- Float (and complex) literals in source code were evaluated to full
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precision only when running from a .py file; the same code loaded from a
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.pyc (or .pyo) file could suffer numeric differences starting at about the
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12th significant decimal digit. For example, on a machine with IEEE-754
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floating arithmetic,
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x = 9007199254740992.0
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print long(x)
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printed 9007199254740992 if run directly from .py, but 9007199254740000
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if from a compiled (.pyc or .pyo) file. This was due to marshal using
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str(float) instead of repr(float) when building code objects. marshal
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now uses repr(float) instead, which should reproduce floats to full
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machine precision (assuming the platform C float<->string I/O conversion
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functions are of good quality).
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This may cause floating-point results to change in some cases, and
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usually for the better, but may also cause numerically unstable
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algorithms to break.
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- The implementation of dicts suffers fewer collisions, which has speed
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benefits. However, the order in which dict entries appear in dict.keys(),
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dict.values() and dict.items() may differ from previous releases for a
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given dict. Nothing is defined about this order, so no program should
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rely on it. Nevertheless, it's easy to write test cases that rely on the
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order by accident, typically because of printing the str() or repr() of a
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dict to an "expected results" file. See Lib/test/test_support.py's new
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sortdict(dict) function for a simple way to display a dict in sorted
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order.
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- Many other small changes to dicts were made, resulting in faster
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operation along the most common code paths.
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- Dictionary objects now support the "in" operator: "x in dict" means
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the same as dict.has_key(x).
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- The update() method of dictionaries now accepts generic mapping
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objects. Specifically the argument object must support the .keys()
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and __getitem__() methods. This allows you to say, for example,
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{}.update(UserDict())
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- Iterators were added; this is a generalized way of providing values
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to a for loop. See PEP 234. There's a new built-in function iter()
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to return an iterator. There's a new protocol to get the next value
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from an iterator using the next() method (in Python) or the
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tp_iternext slot (in C). There's a new protocol to get iterators
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using the __iter__() method (in Python) or the tp_iter slot (in C).
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Iterating (i.e. a for loop) over a dictionary generates its keys.
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Iterating over a file generates its lines.
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- The following functions were generalized to work nicely with iterator
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arguments:
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map(), filter(), reduce(), zip()
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list(), tuple() (PySequence_Tuple() and PySequence_Fast() in C API)
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max(), min()
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join() method of strings
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extend() method of lists
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'x in y' and 'x not in y' (PySequence_Contains() in C API)
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operator.countOf() (PySequence_Count() in C API)
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right-hand side of assignment statements with multiple targets, such as
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x, y, z = some_iterable_object_returning_exactly_3_values
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- Accessing module attributes is significantly faster (for example,
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random.random or os.path or yourPythonModule.yourAttribute).
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- Comparing dictionary objects via == and != is faster, and now works even
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if the keys and values don't support comparisons other than ==.
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|
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- Comparing dictionaries in ways other than == and != is slower: there were
|
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insecurities in the dict comparison implementation that could cause Python
|
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to crash if the element comparison routines for the dict keys and/or
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values mutated the dicts. Making the code bulletproof slowed it down.
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- Collisions in dicts are resolved via a new approach, which can help
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dramatically in bad cases. For example, looking up every key in a dict
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d with d.keys() == [i << 16 for i in range(20000)] is approximately 500x
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faster now. Thanks to Christian Tismer for pointing out the cause and
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the nature of an effective cure (last December! better late than never).
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- repr() is much faster for large containers (dict, list, tuple).
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Library
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- The constants ascii_letters, ascii_lowercase. and ascii_uppercase
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were added to the string module. These a locale-indenpendent
|
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constants, unlike letters, lowercase, and uppercase. These are now
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use in appropriate locations in the standard library.
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- The flags used in dlopen calls can now be configured using
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sys.setdlopenflags and queried using sys.getdlopenflags.
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- Fredrik Lundh's xmlrpclib is now a standard library module. This
|
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provides full client-side XML-RPC support. In addition,
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Demo/xmlrpc/ contains two server frameworks (one SocketServer-based,
|
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one asyncore-based). Thanks to Eric Raymond for the documentation.
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- The xrange() object is simplified: it no longer supports slicing,
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repetition, comparisons, efficient 'in' checking, the tolist()
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method, or the start, stop and step attributes. See PEP 260.
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- A new function fnmatch.filter to filter lists of file names was added.
|
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- calendar.py uses month and day names based on the current locale.
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|
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- strop is now *really* obsolete (this was announced before with 1.6),
|
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and issues DeprecationWarning when used (except for the four items
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that are still imported into string.py).
|
||
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- Cookie.py now sorts key+value pairs by key in output strings.
|
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|
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- pprint.isrecursive(object) didn't correctly identify recursive objects.
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Now it does.
|
||
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- pprint functions now much faster for large containers (tuple, list, dict).
|
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- New 'q' and 'Q' format codes in the struct module, corresponding to C
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types "long long" and "unsigned long long" (on Windows, __int64). In
|
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native mode, these can be used only when the platform C compiler supports
|
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these types (when HAVE_LONG_LONG is #define'd by the Python config
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process), and then they inherit the sizes and alignments of the C types.
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In standard mode, 'q' and 'Q' are supported on all platforms, and are
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8-byte integral types.
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- The site module installs a new built-in function 'help' that invokes
|
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pydoc.help. It must be invoked as 'help()'; when invoked as 'help',
|
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it displays a message reminding the user to use 'help()' or
|
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'help(object)'.
|
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|
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Tests
|
||
|
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- New test_mutants.py runs dict comparisons where the key and value
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comparison operators mutute the dicts randomly during comparison. This
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rapidly causes Python to crash under earlier releases (not for the faint
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of heart: it can also cause Win9x to freeze or reboot!).
|
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|
||
- New test_pprint.py verfies that pprint.isrecursive() and
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pprint.isreadable() return sensible results. Also verifies that simple
|
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cases produce correct output.
|
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|
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New platforms
|
||
|
||
- Python should compile and run out of the box using the Borland C
|
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compiler (under Windows), thanks to Stephen Hansen.
|
||
|
||
C API
|
||
|
||
- Removed the unused last_is_sticky argument from the internal
|
||
_PyTuple_Resize(). If this affects you, you were cheating.
|
||
|
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|
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======================================================================
|
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|
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|
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What's New in Python 2.1 (final)?
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=================================
|
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|
||
We only changed a few things since the last release candidate, all in
|
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Python library code:
|
||
|
||
- A bug in the locale module was fixed that affected locales which
|
||
define no grouping for numeric formatting.
|
||
|
||
- A few bugs in the weakref module's implementations of weak
|
||
dictionaries (WeakValueDictionary and WeakKeyDictionary) were fixed,
|
||
and the test suite was updated to check for these bugs.
|
||
|
||
- An old bug in the os.path.walk() function (introduced in Python
|
||
2.0!) was fixed: a non-existent file would cause an exception
|
||
instead of being ignored.
|
||
|
||
- Fixed a few bugs in the new symtable module found by Neil Norwitz's
|
||
PyChecker.
|
||
|
||
|
||
What's New in Python 2.1c2?
|
||
===========================
|
||
|
||
A flurry of small changes, and one showstopper fixed in the nick of
|
||
time made it necessary to release another release candidate. The list
|
||
here is the *complete* list of patches (except version updates):
|
||
|
||
Core
|
||
|
||
- Tim discovered a nasty bug in the dictionary code, caused by
|
||
PyDict_Next() calling dict_resize(), and the GC code's use of
|
||
PyDict_Next() violating an assumption in dict_items(). This was
|
||
fixed with considerable amounts of band-aid, but the net effect is a
|
||
saner and more robust implementation.
|
||
|
||
- Made a bunch of symbols static that were accidentally global.
|
||
|
||
Build and Ports
|
||
|
||
- The setup.py script didn't check for a new enough version of zlib
|
||
(1.1.3 is needed). Now it does.
|
||
|
||
- Changed "make clean" target to also remove shared libraries.
|
||
|
||
- Added a more general warning about the SGI Irix optimizer to README.
|
||
|
||
Library
|
||
|
||
- Fix a bug in urllib.basejoin("http://host", "../file.html") which
|
||
omitted the slash between host and file.html.
|
||
|
||
- The mailbox module's _Mailbox class contained a completely broken
|
||
and undocumented seek() method. Ripped it out.
|
||
|
||
- Fixed a bunch of typos in various library modules (urllib2, smtpd,
|
||
sgmllib, netrc, chunk) found by Neil Norwitz's PyChecker.
|
||
|
||
- Fixed a few last-minute bugs in unittest.
|
||
|
||
Extensions
|
||
|
||
- Reverted the patch to the OpenSSL code in socketmodule.c to support
|
||
RAND_status() and the EGD, and the subsequent patch that tried to
|
||
fix it for pre-0.9.5 versions; the problem with the patch is that on
|
||
some systems it issues a warning whenever socket is imported, and
|
||
that's unacceptable.
|
||
|
||
Tests
|
||
|
||
- Fixed the pickle tests to work with "import test.test_pickle".
|
||
|
||
- Tweaked test_locale.py to actually run the test Windows.
|
||
|
||
- In distutils/archive_util.py, call zipfile.ZipFile() with mode "w",
|
||
not "wb" (which is not a valid mode at all).
|
||
|
||
- Fix pstats browser crashes. Import readline if it exists to make
|
||
the user interface nicer.
|
||
|
||
- Add "import thread" to the top of test modules that import the
|
||
threading module (test_asynchat and test_threadedtempfile). This
|
||
prevents test failures caused by a broken threading module resulting
|
||
from a previously caught failed import.
|
||
|
||
- Changed test_asynchat.py to set the SO_REUSEADDR option; this was
|
||
needed on some platforms (e.g. Solaris 8) when the tests are run
|
||
twice in succession.
|
||
|
||
- Skip rather than fail test_sunaudiodev if no audio device is found.
|
||
|
||
|
||
What's New in Python 2.1c1?
|
||
===========================
|
||
|
||
This list was significantly updated when 2.1c2 was released; the 2.1c1
|
||
release didn't mention most changes that were actually part of 2.1c1:
|
||
|
||
Legal
|
||
|
||
- Copyright was assigned to the Python Software Foundation (PSF) and a
|
||
PSF license (very similar to the CNRI license) was added.
|
||
|
||
- The CNRI copyright notice was updated to include 2001.
|
||
|
||
Core
|
||
|
||
- After a public outcry, assignment to __debug__ is no longer illegal;
|
||
instead, a warning is issued. It will become illegal in 2.2.
|
||
|
||
- Fixed a core dump with "%#x" % 0, and changed the semantics so that
|
||
"%#x" now always prepends "0x", even if the value is zero.
|
||
|
||
- Fixed some nits in the bytecode compiler.
|
||
|
||
- Fixed core dumps when calling certain kinds of non-functions.
|
||
|
||
- Fixed various core dumps caused by reference count bugs.
|
||
|
||
Build and Ports
|
||
|
||
- Use INSTALL_SCRIPT to install script files.
|
||
|
||
- New port: SCO Unixware 7, by Billy G. Allie.
|
||
|
||
- Updated RISCOS port.
|
||
|
||
- Updated BeOS port and notes.
|
||
|
||
- Various other porting problems resolved.
|
||
|
||
Library
|
||
|
||
- The TERMIOS and SOCKET modules are now truly obsolete and
|
||
unnecessary. Their symbols are incorporated in the termios and
|
||
socket modules.
|
||
|
||
- Fixed some 64-bit bugs in pickle, cPickle, and struct, and added
|
||
better tests for pickling.
|
||
|
||
- threading: make Condition.wait() robust against KeyboardInterrupt.
|
||
|
||
- zipfile: add support to zipfile to support opening an archive
|
||
represented by an open file rather than a file name. Fix bug where
|
||
the archive was not properly closed. Fixed a bug in this bugfix
|
||
where flush() was called for a read-only file.
|
||
|
||
- imputil: added an uninstall() method to the ImportManager.
|
||
|
||
- Canvas: fixed bugs in lower() and tkraise() methods.
|
||
|
||
- SocketServer: API change (added overridable close_request() method)
|
||
so that the TCP server can explicitly close the request.
|
||
|
||
- pstats: Eric Raymond added a simple interactive statistics browser,
|
||
invoked when the module is run as a script.
|
||
|
||
- locale: fixed a problem in format().
|
||
|
||
- webbrowser: made it work when the BROWSER environment variable has a
|
||
value like "/usr/bin/netscape". Made it auto-detect Konqueror for
|
||
KDE 2. Fixed some other nits.
|
||
|
||
- unittest: changes to allow using a different exception than
|
||
AssertionError, and added a few more function aliases. Some other
|
||
small changes.
|
||
|
||
- urllib, urllib2: fixed redirect problems and a coupleof other nits.
|
||
|
||
- asynchat: fixed a critical bug in asynchat that slipped through the
|
||
2.1b2 release. Fixed another rare bug.
|
||
|
||
- Fix some unqualified except: clauses (always a bad code example).
|
||
|
||
XML
|
||
|
||
- pyexpat: new API get_version_string().
|
||
|
||
- Fixed some minidom bugs.
|
||
|
||
Extensions
|
||
|
||
- Fixed a core dump in _weakref. Removed the weakref.mapping()
|
||
function (it adds nothing to the API).
|
||
|
||
- Rationalized the use of header files in the readline module, to make
|
||
it compile (albeit with some warnings) with the very recent readline
|
||
4.2, without breaking for earlier versions.
|
||
|
||
- Hopefully fixed a buffering problem in linuxaudiodev.
|
||
|
||
- Attempted a fix to make the OpenSSL support in the socket module
|
||
work again with pre-0.9.5 versions of OpenSSL.
|
||
|
||
Tests
|
||
|
||
- Added a test case for asynchat and asyncore.
|
||
|
||
- Removed coupling between tests where one test failing could break
|
||
another.
|
||
|
||
Tools
|
||
|
||
- Ping added an interactive help browser to pydoc, fixed some nits
|
||
in the rest of the pydoc code, and added some features to his
|
||
inspect module.
|
||
|
||
- An updated python-mode.el version 4.1 which integrates Ken
|
||
Manheimer's pdbtrack.el. This makes debugging Python code via pdb
|
||
much nicer in XEmacs and Emacs. When stepping through your program
|
||
with pdb, in either the shell window or the *Python* window, the
|
||
source file and line will be tracked by an arrow. Very cool!
|
||
|
||
- IDLE: syntax warnings in interactive mode are changed into errors.
|
||
|
||
- Some improvements to Tools/webchecker (ignore some more URL types,
|
||
follow some more links).
|
||
|
||
- Brought the Tools/compiler package up to date.
|
||
|
||
|
||
What's New in Python 2.1 beta 2?
|
||
================================
|
||
|
||
(Unlisted are many fixed bugs, more documentation, etc.)
|
||
|
||
Core language, builtins, and interpreter
|
||
|
||
- The nested scopes work (enabled by "from __future__ import
|
||
nested_scopes") is completed; in particular, the future now extends
|
||
into code executed through exec, eval() and execfile(), and into the
|
||
interactive interpreter.
|
||
|
||
- When calling a base class method (e.g. BaseClass.__init__(self)),
|
||
this is now allowed even if self is not strictly spoken a class
|
||
instance (e.g. when using metaclasses or the Don Beaudry hook).
|
||
|
||
- Slice objects are now comparable but not hashable; this prevents
|
||
dict[:] from being accepted but meaningless.
|
||
|
||
- Complex division is now calculated using less braindead algorithms.
|
||
This doesn't change semantics except it's more likely to give useful
|
||
results in extreme cases. Complex repr() now uses full precision
|
||
like float repr().
|
||
|
||
- sgmllib.py now calls handle_decl() for simple <!...> declarations.
|
||
|
||
- It is illegal to assign to the name __debug__, which is set when the
|
||
interpreter starts. It is effectively a compile-time constant.
|
||
|
||
- A warning will be issued if a global statement for a variable
|
||
follows a use or assignment of that variable.
|
||
|
||
Standard library
|
||
|
||
- unittest.py, a unit testing framework by Steve Purcell (PyUNIT,
|
||
inspired by JUnit), is now part of the standard library. You now
|
||
have a choice of two testing frameworks: unittest requires you to
|
||
write testcases as separate code, doctest gathers them from
|
||
docstrings. Both approaches have their advantages and
|
||
disadvantages.
|
||
|
||
- A new module Tix was added, which wraps the Tix extension library
|
||
for Tk. With that module, it is not necessary to statically link
|
||
Tix with _tkinter, since Tix will be loaded with Tcl's "package
|
||
require" command. See Demo/tix/.
|
||
|
||
- tzparse.py is now obsolete.
|
||
|
||
- In gzip.py, the seek() and tell() methods are removed -- they were
|
||
non-functional anyway, and it's better if callers can test for their
|
||
existence with hasattr().
|
||
|
||
Python/C API
|
||
|
||
- PyDict_Next(): it is now safe to call PyDict_SetItem() with a key
|
||
that's already in the dictionary during a PyDict_Next() iteration.
|
||
This used to fail occasionally when a dictionary resize operation
|
||
could be triggered that would rehash all the keys. All other
|
||
modifications to the dictionary are still off-limits during a
|
||
PyDict_Next() iteration!
|
||
|
||
- New extended APIs related to passing compiler variables around.
|
||
|
||
- New abstract APIs PyObject_IsInstance(), PyObject_IsSubclass()
|
||
implement isinstance() and issubclass().
|
||
|
||
- Py_BuildValue() now has a "D" conversion to create a Python complex
|
||
number from a Py_complex C value.
|
||
|
||
- Extensions types which support weak references must now set the
|
||
field allocated for the weak reference machinery to NULL themselves;
|
||
this is done to avoid the cost of checking each object for having a
|
||
weakly referencable type in PyObject_INIT(), since most types are
|
||
not weakly referencable.
|
||
|
||
- PyFrame_FastToLocals() and PyFrame_LocalsToFast() copy bindings for
|
||
free variables and cell variables to and from the frame's f_locals.
|
||
|
||
- Variants of several functions defined in pythonrun.h have been added
|
||
to support the nested_scopes future statement. The variants all end
|
||
in Flags and take an extra argument, a PyCompilerFlags *; examples:
|
||
PyRun_AnyFileExFlags(), PyRun_InteractiveLoopFlags(). These
|
||
variants may be removed in Python 2.2, when nested scopes are
|
||
mandatory.
|
||
|
||
Distutils
|
||
|
||
- the sdist command now writes a PKG-INFO file, as described in PEP 241,
|
||
into the release tree.
|
||
|
||
- several enhancements to the bdist_wininst command from Thomas Heller
|
||
(an uninstaller, more customization of the installer's display)
|
||
|
||
- from Jack Jansen: added Mac-specific code to generate a dialog for
|
||
users to specify the command-line (because providing a command-line with
|
||
MacPython is awkward). Jack also made various fixes for the Mac
|
||
and the Metrowerks compiler.
|
||
|
||
- added 'platforms' and 'keywords' to the set of metadata that can be
|
||
specified for a distribution.
|
||
|
||
- applied patches from Jason Tishler to make the compiler class work with
|
||
Cygwin.
|
||
|
||
|
||
What's New in Python 2.1 beta 1?
|
||
================================
|
||
|
||
Core language, builtins, and interpreter
|
||
|
||
- Following an outcry from the community about the amount of code
|
||
broken by the nested scopes feature introduced in 2.1a2, we decided
|
||
to make this feature optional, and to wait until Python 2.2 (or at
|
||
least 6 months) to make it standard. The option can be enabled on a
|
||
per-module basis by adding "from __future__ import nested_scopes" at
|
||
the beginning of a module (before any other statements, but after
|
||
comments and an optional docstring). See PEP 236 (Back to the
|
||
__future__) for a description of the __future__ statement. PEP 227
|
||
(Statically Nested Scopes) has been updated to reflect this change,
|
||
and to clarify the semantics in a number of endcases.
|
||
|
||
- The nested scopes code, when enabled, has been hardened, and most
|
||
bugs and memory leaks in it have been fixed.
|
||
|
||
- Compile-time warnings are now generated for a number of conditions
|
||
that will break or change in meaning when nested scopes are enabled:
|
||
|
||
- Using "from...import *" or "exec" without in-clause in a function
|
||
scope that also defines a lambda or nested function with one or
|
||
more free (non-local) variables. The presence of the import* or
|
||
bare exec makes it impossible for the compiler to determine the
|
||
exact set of local variables in the outer scope, which makes it
|
||
impossible to determine the bindings for free variables in the
|
||
inner scope. To avoid the warning about import *, change it into
|
||
an import of explicitly name object, or move the import* statement
|
||
to the global scope; to avoid the warning about bare exec, use
|
||
exec...in... (a good idea anyway -- there's a possibility that
|
||
bare exec will be deprecated in the future).
|
||
|
||
- Use of a global variable in a nested scope with the same name as a
|
||
local variable in a surrounding scope. This will change in
|
||
meaning with nested scopes: the name in the inner scope will
|
||
reference the variable in the outer scope rather than the global
|
||
of the same name. To avoid the warning, either rename the outer
|
||
variable, or use a global statement in the inner function.
|
||
|
||
- An optional object allocator has been included. This allocator is
|
||
optimized for Python objects and should be faster and use less memory
|
||
than the standard system allocator. It is not enabled by default
|
||
because of possible thread safety problems. The allocator is only
|
||
protected by the Python interpreter lock and it is possible that some
|
||
extension modules require a thread safe allocator. The object
|
||
allocator can be enabled by providing the "--with-pymalloc" option to
|
||
configure.
|
||
|
||
Standard library
|
||
|
||
- pyexpat now detects the expat version if expat.h defines it. A
|
||
number of additional handlers are provided, which are only available
|
||
since expat 1.95. In addition, the methods SetParamEntityParsing and
|
||
GetInputContext of Parser objects are available with 1.95.x
|
||
only. Parser objects now provide the ordered_attributes and
|
||
specified_attributes attributes. A new module expat.model was added,
|
||
which offers a number of additional constants if 1.95.x is used.
|
||
|
||
- xml.dom offers the new functions registerDOMImplementation and
|
||
getDOMImplementation.
|
||
|
||
- xml.dom.minidom offers a toprettyxml method. A number of DOM
|
||
conformance issues have been resolved. In particular, Element now
|
||
has an hasAttributes method, and the handling of namespaces was
|
||
improved.
|
||
|
||
- Ka-Ping Yee contributed two new modules: inspect.py, a module for
|
||
getting information about live Python code, and pydoc.py, a module
|
||
for interactively converting docstrings to HTML or text.
|
||
Tools/scripts/pydoc, which is now automatically installed into
|
||
<prefix>/bin, uses pydoc.py to display documentation; try running
|
||
"pydoc -h" for instructions. "pydoc -g" pops up a small GUI that
|
||
lets you browse the module docstrings using a web browser.
|
||
|
||
- New library module difflib.py, primarily packaging the SequenceMatcher
|
||
class at the heart of the popular ndiff.py file-comparison tool.
|
||
|
||
- doctest.py (a framework for verifying Python code examples in docstrings)
|
||
is now part of the std library.
|
||
|
||
Windows changes
|
||
|
||
- A new entry in the Start menu, "Module Docs", runs "pydoc -g" -- a
|
||
small GUI that lets you browse the module docstrings using your
|
||
default web browser.
|
||
|
||
- Import is now case-sensitive. PEP 235 (Import on Case-Insensitive
|
||
Platforms) is implemented. See
|
||
|
||
http://python.sourceforge.net/peps/pep-0235.html
|
||
|
||
for full details, especially the "Current Lower-Left Semantics" section.
|
||
The new Windows import rules are simpler than before:
|
||
|
||
A. If the PYTHONCASEOK environment variable exists, same as
|
||
before: silently accept the first case-insensitive match of any
|
||
kind; raise ImportError if none found.
|
||
|
||
B. Else search sys.path for the first case-sensitive match; raise
|
||
ImportError if none found.
|
||
|
||
The same rules have been implented on other platforms with case-
|
||
insensitive but case-preserving filesystems too (including Cygwin, and
|
||
several flavors of Macintosh operating systems).
|
||
|
||
- winsound module: Under Win9x, winsound.Beep() now attempts to simulate
|
||
what it's supposed to do (and does do under NT and 2000) via direct
|
||
port manipulation. It's unknown whether this will work on all systems,
|
||
but it does work on my Win98SE systems now and was known to be useless on
|
||
all Win9x systems before.
|
||
|
||
- Build: Subproject _test (effectively) renamed to _testcapi.
|
||
|
||
New platforms
|
||
|
||
- 2.1 should compile and run out of the box under MacOS X, even using HFS+.
|
||
Thanks to Steven Majewski!
|
||
|
||
- 2.1 should compile and run out of the box on Cygwin. Thanks to Jason
|
||
Tishler!
|
||
|
||
- 2.1 contains new files and patches for RISCOS, thanks to Dietmar
|
||
Schwertberger! See RISCOS/README for more information -- it seems
|
||
that because of the bizarre filename conventions on RISCOS, no port
|
||
to that platform is easy. Note that the new variable os.endsep is
|
||
silently supported in order to make life easier on this platform,
|
||
but we don't advertise it because it's not worth for most folks to
|
||
care about RISCOS portability.
|
||
|
||
|
||
What's New in Python 2.1 alpha 2?
|
||
=================================
|
||
|
||
Core language, builtins, and interpreter
|
||
|
||
- Scopes nest. If a name is used in a function or class, but is not
|
||
local, the definition in the nearest enclosing function scope will
|
||
be used. One consequence of this change is that lambda statements
|
||
could reference variables in the namespaces where the lambda is
|
||
defined. In some unusual cases, this change will break code.
|
||
|
||
In all previous version of Python, names were resolved in exactly
|
||
three namespaces -- the local namespace, the global namespace, and
|
||
the builtin namespace. According to this old definition, if a
|
||
function A is defined within a function B, the names bound in B are
|
||
not visible in A. The new rules make names bound in B visible in A,
|
||
unless A contains a name binding that hides the binding in B.
|
||
|
||
Section 4.1 of the reference manual describes the new scoping rules
|
||
in detail. The test script in Lib/test/test_scope.py demonstrates
|
||
some of the effects of the change.
|
||
|
||
The new rules will cause existing code to break if it defines nested
|
||
functions where an outer function has local variables with the same
|
||
name as globals or builtins used by the inner function. Example:
|
||
|
||
def munge(str):
|
||
def helper(x):
|
||
return str(x)
|
||
if type(str) != type(''):
|
||
str = helper(str)
|
||
return str.strip()
|
||
|
||
Under the old rules, the name str in helper() is bound to the
|
||
builtin function str(). Under the new rules, it will be bound to
|
||
the argument named str and an error will occur when helper() is
|
||
called.
|
||
|
||
- The compiler will report a SyntaxError if "from ... import *" occurs
|
||
in a function or class scope. The language reference has documented
|
||
that this case is illegal, but the compiler never checked for it.
|
||
The recent introduction of nested scope makes the meaning of this
|
||
form of name binding ambiguous. In a future release, the compiler
|
||
may allow this form when there is no possibility of ambiguity.
|
||
|
||
- repr(string) is easier to read, now using hex escapes instead of octal,
|
||
and using \t, \n and \r instead of \011, \012 and \015 (respectively):
|
||
|
||
>>> "\texample \r\n" + chr(0) + chr(255)
|
||
'\texample \r\n\x00\xff' # in 2.1
|
||
'\011example \015\012\000\377' # in 2.0
|
||
|
||
- Functions are now compared and hashed by identity, not by value, since
|
||
the func_code attribute is writable.
|
||
|
||
- Weak references (PEP 205) have been added. This involves a few
|
||
changes in the core, an extension module (_weakref), and a Python
|
||
module (weakref). The weakref module is the public interface. It
|
||
includes support for "explicit" weak references, proxy objects, and
|
||
mappings with weakly held values.
|
||
|
||
- A 'continue' statement can now appear in a try block within the body
|
||
of a loop. It is still not possible to use continue in a finally
|
||
clause.
|
||
|
||
Standard library
|
||
|
||
- mailbox.py now has a new class, PortableUnixMailbox which is
|
||
identical to UnixMailbox but uses a more portable scheme for
|
||
determining From_ separators. Also, the constructors for all the
|
||
classes in this module have a new optional `factory' argument, which
|
||
is a callable used when new message classes must be instantiated by
|
||
the next() method.
|
||
|
||
- random.py is now self-contained, and offers all the functionality of
|
||
the now-deprecated whrandom.py. See the docs for details. random.py
|
||
also supports new functions getstate() and setstate(), for saving
|
||
and restoring the internal state of the generator; and jumpahead(n),
|
||
for quickly forcing the internal state to be the same as if n calls to
|
||
random() had been made. The latter is particularly useful for multi-
|
||
threaded programs, creating one instance of the random.Random() class for
|
||
each thread, then using .jumpahead() to force each instance to use a
|
||
non-overlapping segment of the full period.
|
||
|
||
- random.py's seed() function is new. For bit-for-bit compatibility with
|
||
prior releases, use the whseed function instead. The new seed function
|
||
addresses two problems: (1) The old function couldn't produce more than
|
||
about 2**24 distinct internal states; the new one about 2**45 (the best
|
||
that can be done in the Wichmann-Hill generator). (2) The old function
|
||
sometimes produced identical internal states when passed distinct
|
||
integers, and there was no simple way to predict when that would happen;
|
||
the new one guarantees to produce distinct internal states for all
|
||
arguments in [0, 27814431486576L).
|
||
|
||
- The socket module now supports raw packets on Linux. The socket
|
||
family is AF_PACKET.
|
||
|
||
- test_capi.py is a start at running tests of the Python C API. The tests
|
||
are implemented by the new Modules/_testmodule.c.
|
||
|
||
- A new extension module, _symtable, provides provisional access to the
|
||
internal symbol table used by the Python compiler. A higher-level
|
||
interface will be added on top of _symtable in a future release.
|
||
|
||
- Removed the obsolete soundex module.
|
||
|
||
- xml.dom.minidom now uses the standard DOM exceptions. Node supports
|
||
the isSameNode method; NamedNodeMap the get method.
|
||
|
||
- xml.sax.expatreader supports the lexical handler property; it
|
||
generates comment, startCDATA, and endCDATA events.
|
||
|
||
Windows changes
|
||
|
||
- Build procedure: the zlib project is built in a different way that
|
||
ensures the zlib header files used can no longer get out of synch with
|
||
the zlib binary used. See PCbuild\readme.txt for details. Your old
|
||
zlib-related directories can be deleted; you'll need to download fresh
|
||
source for zlib and unpack it into a new directory.
|
||
|
||
- Build: New subproject _test for the benefit of test_capi.py (see above).
|
||
|
||
- Build: New subproject _symtable, for new DLL _symtable.pyd (a nascent
|
||
interface to some Python compiler internals).
|
||
|
||
- Build: Subproject ucnhash is gone, since the code was folded into the
|
||
unicodedata subproject.
|
||
|
||
What's New in Python 2.1 alpha 1?
|
||
=================================
|
||
|
||
Core language, builtins, and interpreter
|
||
|
||
- There is a new Unicode companion to the PyObject_Str() API
|
||
called PyObject_Unicode(). It behaves in the same way as the
|
||
former, but assures that the returned value is an Unicode object
|
||
(applying the usual coercion if necessary).
|
||
|
||
- The comparison operators support "rich comparison overloading" (PEP
|
||
207). C extension types can provide a rich comparison function in
|
||
the new tp_richcompare slot in the type object. The cmp() function
|
||
and the C function PyObject_Compare() first try the new rich
|
||
comparison operators before trying the old 3-way comparison. There
|
||
is also a new C API PyObject_RichCompare() (which also falls back on
|
||
the old 3-way comparison, but does not constrain the outcome of the
|
||
rich comparison to a Boolean result).
|
||
|
||
The rich comparison function takes two objects (at least one of
|
||
which is guaranteed to have the type that provided the function) and
|
||
an integer indicating the opcode, which can be Py_LT, Py_LE, Py_EQ,
|
||
Py_NE, Py_GT, Py_GE (for <, <=, ==, !=, >, >=), and returns a Python
|
||
object, which may be NotImplemented (in which case the tp_compare
|
||
slot function is used as a fallback, if defined).
|
||
|
||
Classes can overload individual comparison operators by defining one
|
||
or more of the methods__lt__, __le__, __eq__, __ne__, __gt__,
|
||
__ge__. There are no explicit "reflected argument" versions of
|
||
these; instead, __lt__ and __gt__ are each other's reflection,
|
||
likewise for__le__ and __ge__; __eq__ and __ne__ are their own
|
||
reflection (similar at the C level). No other implications are
|
||
made; in particular, Python does not assume that == is the Boolean
|
||
inverse of !=, or that < is the Boolean inverse of >=. This makes
|
||
it possible to define types with partial orderings.
|
||
|
||
Classes or types that want to implement (in)equality tests but not
|
||
the ordering operators (i.e. unordered types) should implement ==
|
||
and !=, and raise an error for the ordering operators.
|
||
|
||
It is possible to define types whose rich comparison results are not
|
||
Boolean; e.g. a matrix type might want to return a matrix of bits
|
||
for A < B, giving elementwise comparisons. Such types should ensure
|
||
that any interpretation of their value in a Boolean context raises
|
||
an exception, e.g. by defining __nonzero__ (or the tp_nonzero slot
|
||
at the C level) to always raise an exception.
|
||
|
||
- Complex numbers use rich comparisons to define == and != but raise
|
||
an exception for <, <=, > and >=. Unfortunately, this also means
|
||
that cmp() of two complex numbers raises an exception when the two
|
||
numbers differ. Since it is not mathematically meaningful to compare
|
||
complex numbers except for equality, I hope that this doesn't break
|
||
too much code.
|
||
|
||
- The outcome of comparing non-numeric objects of different types is
|
||
not defined by the language, other than that it's arbitrary but
|
||
consistent (see the Reference Manual). An implementation detail changed
|
||
in 2.1a1 such that None now compares less than any other object. Code
|
||
relying on this new behavior (like code that relied on the previous
|
||
behavior) does so at its own risk.
|
||
|
||
- Functions and methods now support getting and setting arbitrarily
|
||
named attributes (PEP 232). Functions have a new __dict__
|
||
(a.k.a. func_dict) which hold the function attributes. Methods get
|
||
and set attributes on their underlying im_func. It is a TypeError
|
||
to set an attribute on a bound method.
|
||
|
||
- The xrange() object implementation has been improved so that
|
||
xrange(sys.maxint) can be used on 64-bit platforms. There's still a
|
||
limitation that in this case len(xrange(sys.maxint)) can't be
|
||
calculated, but the common idiom "for i in xrange(sys.maxint)" will
|
||
work fine as long as the index i doesn't actually reach 2**31.
|
||
(Python uses regular ints for sequence and string indices; fixing
|
||
that is much more work.)
|
||
|
||
- Two changes to from...import:
|
||
|
||
1) "from M import X" now works even if (after loading module M)
|
||
sys.modules['M'] is not a real module; it's basically a getattr()
|
||
operation with AttributeError exceptions changed into ImportError.
|
||
|
||
2) "from M import *" now looks for M.__all__ to decide which names to
|
||
import; if M.__all__ doesn't exist, it uses M.__dict__.keys() but
|
||
filters out names starting with '_' as before. Whether or not
|
||
__all__ exists, there's no restriction on the type of M.
|
||
|
||
- File objects have a new method, xreadlines(). This is the fastest
|
||
way to iterate over all lines in a file:
|
||
|
||
for line in file.xreadlines():
|
||
...do something to line...
|
||
|
||
See the xreadlines module (mentioned below) for how to do this for
|
||
other file-like objects.
|
||
|
||
- Even if you don't use file.xreadlines(), you may expect a speedup on
|
||
line-by-line input. The file.readline() method has been optimized
|
||
quite a bit in platform-specific ways: on systems (like Linux) that
|
||
support flockfile(), getc_unlocked(), and funlockfile(), those are
|
||
used by default. On systems (like Windows) without getc_unlocked(),
|
||
a complicated (but still thread-safe) method using fgets() is used by
|
||
default.
|
||
|
||
You can force use of the fgets() method by #define'ing
|
||
USE_FGETS_IN_GETLINE at build time (it may be faster than
|
||
getc_unlocked()).
|
||
|
||
You can force fgets() not to be used by #define'ing
|
||
DONT_USE_FGETS_IN_GETLINE (this is the first thing to try if std test
|
||
test_bufio.py fails -- and let us know if it does!).
|
||
|
||
- In addition, the fileinput module, while still slower than the other
|
||
methods on most platforms, has been sped up too, by using
|
||
file.readlines(sizehint).
|
||
|
||
- Support for run-time warnings has been added, including a new
|
||
command line option (-W) to specify the disposition of warnings.
|
||
See the description of the warnings module below.
|
||
|
||
- Extensive changes have been made to the coercion code. This mostly
|
||
affects extension modules (which can now implement mixed-type
|
||
numerical operators without having to use coercion), but
|
||
occasionally, in boundary cases the coercion semantics have changed
|
||
subtly. Since this was a terrible gray area of the language, this
|
||
is considered an improvement. Also note that __rcmp__ is no longer
|
||
supported -- instead of calling __rcmp__, __cmp__ is called with
|
||
reflected arguments.
|
||
|
||
- In connection with the coercion changes, a new built-in singleton
|
||
object, NotImplemented is defined. This can be returned for
|
||
operations that wish to indicate they are not implemented for a
|
||
particular combination of arguments. From C, this is
|
||
Py_NotImplemented.
|
||
|
||
- The interpreter accepts now bytecode files on the command line even
|
||
if they do not have a .pyc or .pyo extension. On Linux, after executing
|
||
|
||
import imp,sys,string
|
||
magic = string.join(["\\x%.2x" % ord(c) for c in imp.get_magic()],"")
|
||
reg = ':pyc:M::%s::%s:' % (magic, sys.executable)
|
||
open("/proc/sys/fs/binfmt_misc/register","wb").write(reg)
|
||
|
||
any byte code file can be used as an executable (i.e. as an argument
|
||
to execve(2)).
|
||
|
||
- %[xXo] formats of negative Python longs now produce a sign
|
||
character. In 1.6 and earlier, they never produced a sign,
|
||
and raised an error if the value of the long was too large
|
||
to fit in a Python int. In 2.0, they produced a sign if and
|
||
only if too large to fit in an int. This was inconsistent
|
||
across platforms (because the size of an int varies across
|
||
platforms), and inconsistent with hex() and oct(). Example:
|
||
|
||
>>> "%x" % -0x42L
|
||
'-42' # in 2.1
|
||
'ffffffbe' # in 2.0 and before, on 32-bit machines
|
||
>>> hex(-0x42L)
|
||
'-0x42L' # in all versions of Python
|
||
|
||
The behavior of %d formats for negative Python longs remains
|
||
the same as in 2.0 (although in 1.6 and before, they raised
|
||
an error if the long didn't fit in a Python int).
|
||
|
||
%u formats don't make sense for Python longs, but are allowed
|
||
and treated the same as %d in 2.1. In 2.0, a negative long
|
||
formatted via %u produced a sign if and only if too large to
|
||
fit in an int. In 1.6 and earlier, a negative long formatted
|
||
via %u raised an error if it was too big to fit in an int.
|
||
|
||
- Dictionary objects have an odd new method, popitem(). This removes
|
||
an arbitrary item from the dictionary and returns it (in the form of
|
||
a (key, value) pair). This can be useful for algorithms that use a
|
||
dictionary as a bag of "to do" items and repeatedly need to pick one
|
||
item. Such algorithms normally end up running in quadratic time;
|
||
using popitem() they can usually be made to run in linear time.
|
||
|
||
Standard library
|
||
|
||
- In the time module, the time argument to the functions strftime,
|
||
localtime, gmtime, asctime and ctime is now optional, defaulting to
|
||
the current time (in the local timezone).
|
||
|
||
- The ftplib module now defaults to passive mode, which is deemed a
|
||
more useful default given that clients are often inside firewalls
|
||
these days. Note that this could break if ftplib is used to connect
|
||
to a *server* that is inside a firewall, from outside; this is
|
||
expected to be a very rare situation. To fix that, you can call
|
||
ftp.set_pasv(0).
|
||
|
||
- The module site now treats .pth files not only for path configuration,
|
||
but also supports extensions to the initialization code: Lines starting
|
||
with import are executed.
|
||
|
||
- There's a new module, warnings, which implements a mechanism for
|
||
issuing and filtering warnings. There are some new built-in
|
||
exceptions that serve as warning categories, and a new command line
|
||
option, -W, to control warnings (e.g. -Wi ignores all warnings, -We
|
||
turns warnings into errors). warnings.warn(message[, category])
|
||
issues a warning message; this can also be called from C as
|
||
PyErr_Warn(category, message).
|
||
|
||
- A new module xreadlines was added. This exports a single factory
|
||
function, xreadlines(). The intention is that this code is the
|
||
absolutely fastest way to iterate over all lines in an open
|
||
file(-like) object:
|
||
|
||
import xreadlines
|
||
for line in xreadlines.xreadlines(file):
|
||
...do something to line...
|
||
|
||
This is equivalent to the previous the speed record holder using
|
||
file.readlines(sizehint). Note that if file is a real file object
|
||
(as opposed to a file-like object), this is equivalent:
|
||
|
||
for line in file.xreadlines():
|
||
...do something to line...
|
||
|
||
- The bisect module has new functions bisect_left, insort_left,
|
||
bisect_right and insort_right. The old names bisect and insort
|
||
are now aliases for bisect_right and insort_right. XXX_right
|
||
and XXX_left methods differ in what happens when the new element
|
||
compares equal to one or more elements already in the list: the
|
||
XXX_left methods insert to the left, the XXX_right methods to the
|
||
right. Code that doesn't care where equal elements end up should
|
||
continue to use the old, short names ("bisect" and "insort").
|
||
|
||
- The new curses.panel module wraps the panel library that forms part
|
||
of SYSV curses and ncurses. Contributed by Thomas Gellekum.
|
||
|
||
- The SocketServer module now sets the allow_reuse_address flag by
|
||
default in the TCPServer class.
|
||
|
||
- A new function, sys._getframe(), returns the stack frame pointer of
|
||
the caller. This is intended only as a building block for
|
||
higher-level mechanisms such as string interpolation.
|
||
|
||
- The pyexpat module supports a number of new handlers, which are
|
||
available only in expat 1.2. If invocation of a callback fails, it
|
||
will report an additional frame in the traceback. Parser objects
|
||
participate now in garbage collection. If expat reports an unknown
|
||
encoding, pyexpat will try to use a Python codec; that works only
|
||
for single-byte charsets. The parser type objects is exposed as
|
||
XMLParserObject.
|
||
|
||
- xml.dom now offers standard definitions for symbolic node type and
|
||
exception code constants, and a hierarchy of DOM exceptions. minidom
|
||
was adjusted to use them.
|
||
|
||
- The conformance of xml.dom.minidom to the DOM specification was
|
||
improved. It detects a number of additional error cases; the
|
||
previous/next relationship works even when the tree is modified;
|
||
Node supports the normalize() method; NamedNodeMap, DocumentType and
|
||
DOMImplementation classes were added; Element supports the
|
||
hasAttribute and hasAttributeNS methods; and Text supports the splitText
|
||
method.
|
||
|
||
Build issues
|
||
|
||
- For Unix (and Unix-compatible) builds, configuration and building of
|
||
extension modules is now greatly automated. Rather than having to
|
||
edit the Modules/Setup file to indicate which modules should be
|
||
built and where their include files and libraries are, a
|
||
distutils-based setup.py script now takes care of building most
|
||
extension modules. All extension modules built this way are built
|
||
as shared libraries. Only a few modules that must be linked
|
||
statically are still listed in the Setup file; you won't need to
|
||
edit their configuration.
|
||
|
||
- Python should now build out of the box on Cygwin. If it doesn't,
|
||
mail to Jason Tishler (jlt63 at users.sourceforge.net).
|
||
|
||
- Python now always uses its own (renamed) implementation of getopt()
|
||
-- there's too much variation among C library getopt()
|
||
implementations.
|
||
|
||
- C++ compilers are better supported; the CXX macro is always set to a
|
||
C++ compiler if one is found.
|
||
|
||
Windows changes
|
||
|
||
- select module: By default under Windows, a select() call
|
||
can specify no more than 64 sockets. Python now boosts
|
||
this Microsoft default to 512. If you need even more than
|
||
that, see the MS docs (you'll need to #define FD_SETSIZE
|
||
and recompile Python from source).
|
||
|
||
- Support for Windows 3.1, DOS and OS/2 is gone. The Lib/dos-8x3
|
||
subdirectory is no more!
|
||
|
||
|
||
What's New in Python 2.0?
|
||
=========================
|
||
|
||
Below is a list of all relevant changes since release 1.6. Older
|
||
changes are in the file HISTORY. If you are making the jump directly
|
||
from Python 1.5.2 to 2.0, make sure to read the section for 1.6 in the
|
||
HISTORY file! Many important changes listed there.
|
||
|
||
Alternatively, a good overview of the changes between 1.5.2 and 2.0 is
|
||
the document "What's New in Python 2.0" by Kuchling and Moshe Zadka:
|
||
http://starship.python.net/crew/amk/python/writing/new-python/.
|
||
|
||
--Guido van Rossum (home page: http://www.pythonlabs.com/~guido/)
|
||
|
||
======================================================================
|
||
|
||
What's new in 2.0 (since release candidate 1)?
|
||
==============================================
|
||
|
||
Standard library
|
||
|
||
- The copy_reg module was modified to clarify its intended use: to
|
||
register pickle support for extension types, not for classes.
|
||
pickle() will raise a TypeError if it is passed a class.
|
||
|
||
- Fixed a bug in gettext's "normalize and expand" code that prevented
|
||
it from finding an existing .mo file.
|
||
|
||
- Restored support for HTTP/0.9 servers in httplib.
|
||
|
||
- The math module was changed to stop raising OverflowError in case of
|
||
underflow, and return 0 instead in underflow cases. Whether Python
|
||
used to raise OverflowError in case of underflow was platform-
|
||
dependent (it did when the platform math library set errno to ERANGE
|
||
on underflow).
|
||
|
||
- Fixed a bug in StringIO that occurred when the file position was not
|
||
at the end of the file and write() was called with enough data to
|
||
extend past the end of the file.
|
||
|
||
- Fixed a bug that caused Tkinter error messages to get lost on
|
||
Windows. The bug was fixed by replacing direct use of
|
||
interp->result with Tcl_GetStringResult(interp).
|
||
|
||
- Fixed bug in urllib2 that caused it to fail when it received an HTTP
|
||
redirect response.
|
||
|
||
- Several changes were made to distutils: Some debugging code was
|
||
removed from util. Fixed the installer used when an external zip
|
||
program (like WinZip) is not found; the source code for this
|
||
installer is in Misc/distutils. check_lib() was modified to behave
|
||
more like AC_CHECK_LIB by add other_libraries() as a parameter. The
|
||
test for whether installed modules are on sys.path was changed to
|
||
use both normcase() and normpath().
|
||
|
||
- Several minor bugs were fixed in the xml package (the minidom,
|
||
pulldom, expatreader, and saxutils modules).
|
||
|
||
- The regression test driver (regrtest.py) behavior when invoked with
|
||
-l changed: It now reports a count of objects that are recognized as
|
||
garbage but not freed by the garbage collector.
|
||
|
||
- The regression test for the math module was changed to test
|
||
exceptional behavior when the test is run in verbose mode. Python
|
||
cannot yet guarantee consistent exception behavior across platforms,
|
||
so the exception part of test_math is run only in verbose mode, and
|
||
may fail on your platform.
|
||
|
||
Internals
|
||
|
||
- PyOS_CheckStack() has been disabled on Win64, where it caused
|
||
test_sre to fail.
|
||
|
||
Build issues
|
||
|
||
- Changed compiler flags, so that gcc is always invoked with -Wall and
|
||
-Wstrict-prototypes. Users compiling Python with GCC should see
|
||
exactly one warning, except if they have passed configure the
|
||
--with-pydebug flag. The expected warning is for getopt() in
|
||
Modules/main.c. This warning will be fixed for Python 2.1.
|
||
|
||
- Fixed configure to add -threads argument during linking on OSF1.
|
||
|
||
Tools and other miscellany
|
||
|
||
- The compiler in Tools/compiler was updated to support the new
|
||
language features introduced in 2.0: extended print statement, list
|
||
comprehensions, and augmented assignments. The new compiler should
|
||
also be backwards compatible with Python 1.5.2; the compiler will
|
||
always generate code for the version of the interpreter it runs
|
||
under.
|
||
|
||
What's new in 2.0 release candidate 1 (since beta 2)?
|
||
=====================================================
|
||
|
||
What is release candidate 1?
|
||
|
||
We believe that release candidate 1 will fix all known bugs that we
|
||
intend to fix for the 2.0 final release. This release should be a bit
|
||
more stable than the previous betas. We would like to see even more
|
||
widespread testing before the final release, so we are producing this
|
||
release candidate. The final release will be exactly the same unless
|
||
any show-stopping (or brown bag) bugs are found by testers of the
|
||
release candidate.
|
||
|
||
All the changes since the last beta release are bug fixes or changes
|
||
to support building Python for specific platforms.
|
||
|
||
Core language, builtins, and interpreter
|
||
|
||
- A bug that caused crashes when __coerce__ was used with augmented
|
||
assignment, e.g. +=, was fixed.
|
||
|
||
- Raise ZeroDivisionError when raising zero to a negative number,
|
||
e.g. 0.0 ** -2.0. Note that math.pow is unrelated to the builtin
|
||
power operator and the result of math.pow(0.0, -2.0) will vary by
|
||
platform. On Linux, it raises a ValueError.
|
||
|
||
- A bug in Unicode string interpolation was fixed that occasionally
|
||
caused errors with formats including "%%". For example, the
|
||
following expression "%% %s" % u"abc" no longer raises a TypeError.
|
||
|
||
- Compilation of deeply nested expressions raises MemoryError instead
|
||
of SyntaxError, e.g. eval("[" * 50 + "]" * 50).
|
||
|
||
- In 2.0b2 on Windows, the interpreter wrote .pyc files in text mode,
|
||
rendering them useless. They are now written in binary mode again.
|
||
|
||
Standard library
|
||
|
||
- Keyword arguments are now accepted for most pattern and match object
|
||
methods in SRE, the standard regular expression engine.
|
||
|
||
- In SRE, fixed error with negative lookahead and lookbehind that
|
||
manifested itself as a runtime error in patterns like "(?<!abc)(def)".
|
||
|
||
- Several bugs in the Unicode handling and error handling in _tkinter
|
||
were fixed.
|
||
|
||
- Fix memory management errors in Merge() and Tkapp_Call() routines.
|
||
|
||
- Several changes were made to cStringIO to make it compatible with
|
||
the file-like object interface and with StringIO. If operations are
|
||
performed on a closed object, an exception is raised. The truncate
|
||
method now accepts a position argument and readline accepts a size
|
||
argument.
|
||
|
||
- There were many changes made to the linuxaudiodev module and its
|
||
test suite; as a result, a short, unexpected audio sample should now
|
||
play when the regression test is run.
|
||
|
||
Note that this module is named poorly, because it should work
|
||
correctly on any platform that supports the Open Sound System
|
||
(OSS).
|
||
|
||
The module now raises exceptions when errors occur instead of
|
||
crashing. It also defines the AFMT_A_LAW format (logarithmic A-law
|
||
audio) and defines a getptr() method that calls the
|
||
SNDCTL_DSP_GETxPTR ioctl defined in the OSS Programmer's Guide.
|
||
|
||
- The library_version attribute, introduced in an earlier beta, was
|
||
removed because it can not be supported with early versions of the C
|
||
readline library, which provides no way to determine the version at
|
||
compile-time.
|
||
|
||
- The binascii module is now enabled on Win64.
|
||
|
||
- tokenize.py no longer suffers "recursion depth" errors when parsing
|
||
programs with very long string literals.
|
||
|
||
Internals
|
||
|
||
- Fixed several buffer overflow vulnerabilities in calculate_path(),
|
||
which is called when the interpreter starts up to determine where
|
||
the standard library is installed. These vulnerabilities affect all
|
||
previous versions of Python and can be exploited by setting very
|
||
long values for PYTHONHOME or argv[0]. The risk is greatest for a
|
||
setuid Python script, although use of the wrapper in
|
||
Misc/setuid-prog.c will eliminate the vulnerability.
|
||
|
||
- Fixed garbage collection bugs in instance creation that were
|
||
triggered when errors occurred during initialization. The solution,
|
||
applied in cPickle and in PyInstance_New(), is to call
|
||
PyObject_GC_Init() after the initialization of the object's
|
||
container attributes is complete.
|
||
|
||
- pyexpat adds definitions of PyModule_AddStringConstant and
|
||
PyModule_AddObject if the Python version is less than 2.0, which
|
||
provides compatibility with PyXML on Python 1.5.2.
|
||
|
||
- If the platform has a bogus definition for LONG_BIT (the number of
|
||
bits in a long), an error will be reported at compile time.
|
||
|
||
- Fix bugs in _PyTuple_Resize() which caused hard-to-interpret garbage
|
||
collection crashes and possibly other, unreported crashes.
|
||
|
||
- Fixed a memory leak in _PyUnicode_Fini().
|
||
|
||
Build issues
|
||
|
||
- configure now accepts a --with-suffix option that specifies the
|
||
executable suffix. This is useful for builds on Cygwin and Mac OS
|
||
X, for example.
|
||
|
||
- The mmap.PAGESIZE constant is now initialized using sysconf when
|
||
possible, which eliminates a dependency on -lucb for Reliant UNIX.
|
||
|
||
- The md5 file should now compile on all platforms.
|
||
|
||
- The select module now compiles on platforms that do not define
|
||
POLLRDNORM and related constants.
|
||
|
||
- Darwin (Mac OS X): Initial support for static builds on this
|
||
platform.
|
||
|
||
- BeOS: A number of changes were made to the build and installation
|
||
process. ar-fake now operates on a directory of object files.
|
||
dl_export.h is gone, and its macros now appear on the mwcc command
|
||
line during build on PPC BeOS.
|
||
|
||
- Platform directory in lib/python2.0 is "plat-beos5" (or
|
||
"plat-beos4", if building on BeOS 4.5), rather than "plat-beos".
|
||
|
||
- Cygwin: Support for shared libraries, Tkinter, and sockets.
|
||
|
||
- SunOS 4.1.4_JL: Fix test for directory existence in configure.
|
||
|
||
Tools and other miscellany
|
||
|
||
- Removed debugging prints from main used with freeze.
|
||
|
||
- IDLE auto-indent no longer crashes when it encounters Unicode
|
||
characters.
|
||
|
||
What's new in 2.0 beta 2 (since beta 1)?
|
||
========================================
|
||
|
||
Core language, builtins, and interpreter
|
||
|
||
- Add support for unbounded ints in %d,i,u,x,X,o formats; for example
|
||
"%d" % 2L**64 == "18446744073709551616".
|
||
|
||
- Add -h and -V command line options to print the usage message and
|
||
Python version number and exit immediately.
|
||
|
||
- eval() and exec accept Unicode objects as code parameters.
|
||
|
||
- getattr() and setattr() now also accept Unicode objects for the
|
||
attribute name, which are converted to strings using the default
|
||
encoding before lookup.
|
||
|
||
- Multiplication on string and Unicode now does proper bounds
|
||
checking; e.g. 'a' * 65536 * 65536 will raise ValueError, "repeated
|
||
string is too long."
|
||
|
||
- Better error message when continue is found in try statement in a
|
||
loop.
|
||
|
||
|
||
Standard library and extensions
|
||
|
||
- socket module: the OpenSSL code now adds support for RAND_status()
|
||
and EGD (Entropy Gathering Device).
|
||
|
||
- array: reverse() method of array now works. buffer_info() now does
|
||
argument checking; it still takes no arguments.
|
||
|
||
- asyncore/asynchat: Included most recent version from Sam Rushing.
|
||
|
||
- cgi: Accept '&' or ';' as separator characters when parsing form data.
|
||
|
||
- CGIHTTPServer: Now works on Windows (and perhaps even Mac).
|
||
|
||
- ConfigParser: When reading the file, options spelled in upper case
|
||
letters are now correctly converted to lowercase.
|
||
|
||
- copy: Copy Unicode objects atomically.
|
||
|
||
- cPickle: Fail gracefully when copy_reg can't be imported.
|
||
|
||
- cStringIO: Implemented readlines() method.
|
||
|
||
- dbm: Add get() and setdefault() methods to dbm object. Add constant
|
||
`library' to module that names the library used. Added doc strings
|
||
and method names to error messages. Uses configure to determine
|
||
which ndbm.h file to include; Berkeley DB's nbdm and GDBM's ndbm is
|
||
now available options.
|
||
|
||
- distutils: Update to version 0.9.3.
|
||
|
||
- dl: Add several dl.RTLD_ constants.
|
||
|
||
- fpectl: Now supported on FreeBSD.
|
||
|
||
- gc: Add DEBUG_SAVEALL option. When enabled all garbage objects
|
||
found by the collector will be saved in gc.garbage. This is useful
|
||
for debugging a program that creates reference cycles.
|
||
|
||
- httplib: Three changes: Restore support for set_debuglevel feature
|
||
of HTTP class. Do not close socket on zero-length response. Do not
|
||
crash when server sends invalid content-length header.
|
||
|
||
- mailbox: Mailbox class conforms better to qmail specifications.
|
||
|
||
- marshal: When reading a short, sign-extend on platforms where shorts
|
||
are bigger than 16 bits. When reading a long, repair the unportable
|
||
sign extension that was being done for 64-bit machines. (It assumed
|
||
that signed right shift sign-extends.)
|
||
|
||
- operator: Add contains(), invert(), __invert__() as aliases for
|
||
__contains__(), inv(), and __inv__() respectively.
|
||
|
||
- os: Add support for popen2() and popen3() on all platforms where
|
||
fork() exists. (popen4() is still in the works.)
|
||
|
||
- os: (Windows only:) Add startfile() function that acts like double-
|
||
clicking on a file in Explorer (or passing the file name to the
|
||
DOS "start" command).
|
||
|
||
- os.path: (Windows, DOS:) Treat trailing colon correctly in
|
||
os.path.join. os.path.join("a:", "b") yields "a:b".
|
||
|
||
- pickle: Now raises ValueError when an invalid pickle that contains
|
||
a non-string repr where a string repr was expected. This behavior
|
||
matches cPickle.
|
||
|
||
- posixfile: Remove broken __del__() method.
|
||
|
||
- py_compile: support CR+LF line terminators in source file.
|
||
|
||
- readline: Does not immediately exit when ^C is hit when readline and
|
||
threads are configured. Adds definition of rl_library_version. (The
|
||
latter addition requires GNU readline 2.2 or later.)
|
||
|
||
- rfc822: Domain literals returned by AddrlistClass method
|
||
getdomainliteral() are now properly wrapped in brackets.
|
||
|
||
- site: sys.setdefaultencoding() should only be called in case the
|
||
standard default encoding ("ascii") is changed. This saves quite a
|
||
few cycles during startup since the first call to
|
||
setdefaultencoding() will initialize the codec registry and the
|
||
encodings package.
|
||
|
||
- socket: Support for size hint in readlines() method of object returned
|
||
by makefile().
|
||
|
||
- sre: Added experimental expand() method to match objects. Does not
|
||
use buffer interface on Unicode strings. Does not hang if group id
|
||
is followed by whitespace.
|
||
|
||
- StringIO: Size hint in readlines() is now supported as documented.
|
||
|
||
- struct: Check ranges for bytes and shorts.
|
||
|
||
- urllib: Improved handling of win32 proxy settings. Fixed quote and
|
||
quote_plus functions so that the always encode a comma.
|
||
|
||
- Tkinter: Image objects are now guaranteed to have unique ids. Set
|
||
event.delta to zero if Tk version doesn't support mousewheel.
|
||
Removed some debugging prints.
|
||
|
||
- UserList: now implements __contains__().
|
||
|
||
- webbrowser: On Windows, use os.startfile() instead of os.popen(),
|
||
which works around a bug in Norton AntiVirus 2000 that leads directly
|
||
to a Blue Screen freeze.
|
||
|
||
- xml: New version detection code allows PyXML to override standard
|
||
XML package if PyXML version is greater than 0.6.1.
|
||
|
||
- xml.dom: DOM level 1 support for basic XML. Includes xml.dom.minidom
|
||
(conventional DOM), and xml.dom.pulldom, which allows building the DOM
|
||
tree only for nodes which are sufficiently interesting to a specific
|
||
application. Does not provide the HTML-specific extensions. Still
|
||
undocumented.
|
||
|
||
- xml.sax: SAX 2 support for Python, including all the handler
|
||
interfaces needed to process XML 1.0 compliant XML. Some
|
||
documentation is already available.
|
||
|
||
- pyexpat: Renamed to xml.parsers.expat since this is part of the new,
|
||
packagized XML support.
|
||
|
||
|
||
C API
|
||
|
||
- Add three new convenience functions for module initialization --
|
||
PyModule_AddObject(), PyModule_AddIntConstant(), and
|
||
PyModule_AddStringConstant().
|
||
|
||
- Cleaned up definition of NULL in C source code; all definitions were
|
||
removed and add #error to Python.h if NULL isn't defined after
|
||
#include of stdio.h.
|
||
|
||
- Py_PROTO() macros that were removed in 2.0b1 have been restored for
|
||
backwards compatibility (at the source level) with old extensions.
|
||
|
||
- A wrapper API was added for signal() and sigaction(). Instead of
|
||
either function, always use PyOS_getsig() to get a signal handler
|
||
and PyOS_setsig() to set one. A new convenience typedef
|
||
PyOS_sighandler_t is defined for the type of signal handlers.
|
||
|
||
- Add PyString_AsStringAndSize() function that provides access to the
|
||
internal data buffer and size of a string object -- or the default
|
||
encoded version of a Unicode object.
|
||
|
||
- PyString_Size() and PyString_AsString() accept Unicode objects.
|
||
|
||
- The standard header <limits.h> is now included by Python.h (if it
|
||
exists). INT_MAX and LONG_MAX will always be defined, even if
|
||
<limits.h> is not available.
|
||
|
||
- PyFloat_FromString takes a second argument, pend, that was
|
||
effectively useless. It is now officially useless but preserved for
|
||
backwards compatibility. If the pend argument is not NULL, *pend is
|
||
set to NULL.
|
||
|
||
- PyObject_GetAttr() and PyObject_SetAttr() now accept Unicode objects
|
||
for the attribute name. See note on getattr() above.
|
||
|
||
- A few bug fixes to argument processing for Unicode.
|
||
PyArg_ParseTupleAndKeywords() now accepts "es#" and "es".
|
||
PyArg_Parse() special cases "s#" for Unicode objects; it returns a
|
||
pointer to the default encoded string data instead of to the raw
|
||
UTF-16.
|
||
|
||
- Py_BuildValue accepts B format (for bgen-generated code).
|
||
|
||
|
||
Internals
|
||
|
||
- On Unix, fix code for finding Python installation directory so that
|
||
it works when argv[0] is a relative path.
|
||
|
||
- Added a true unicode_internal_encode() function and fixed the
|
||
unicode_internal_decode function() to support Unicode objects directly
|
||
rather than by generating a copy of the object.
|
||
|
||
- Several of the internal Unicode tables are much smaller now, and
|
||
the source code should be much friendlier to weaker compilers.
|
||
|
||
- In the garbage collector: Fixed bug in collection of tuples. Fixed
|
||
bug that caused some instances to be removed from the container set
|
||
while they were still live. Fixed parsing in gc.set_debug() for
|
||
platforms where sizeof(long) > sizeof(int).
|
||
|
||
- Fixed refcount problem in instance deallocation that only occurred
|
||
when Py_REF_DEBUG was defined and Py_TRACE_REFS was not.
|
||
|
||
- On Windows, getpythonregpath is now protected against null data in
|
||
registry key.
|
||
|
||
- On Unix, create .pyc/.pyo files with O_EXCL flag to avoid a race
|
||
condition.
|
||
|
||
|
||
Build and platform-specific issues
|
||
|
||
- Better support of GNU Pth via --with-pth configure option.
|
||
|
||
- Python/C API now properly exposed to dynamically-loaded extension
|
||
modules on Reliant UNIX.
|
||
|
||
- Changes for the benefit of SunOS 4.1.4 (really!). mmapmodule.c:
|
||
Don't define MS_SYNC to be zero when it is undefined. Added missing
|
||
prototypes in posixmodule.c.
|
||
|
||
- Improved support for HP-UX build. Threads should now be correctly
|
||
configured (on HP-UX 10.20 and 11.00).
|
||
|
||
- Fix largefile support on older NetBSD systems and OpenBSD by adding
|
||
define for TELL64.
|
||
|
||
|
||
Tools and other miscellany
|
||
|
||
- ftpmirror: Call to main() is wrapped in if __name__ == "__main__".
|
||
|
||
- freeze: The modulefinder now works with 2.0 opcodes.
|
||
|
||
- IDLE:
|
||
Move hackery of sys.argv until after the Tk instance has been
|
||
created, which allows the application-specific Tkinter
|
||
initialization to be executed if present; also pass an explicit
|
||
className parameter to the Tk() constructor.
|
||
|
||
|
||
What's new in 2.0 beta 1?
|
||
=========================
|
||
|
||
Source Incompatibilities
|
||
------------------------
|
||
|
||
None. Note that 1.6 introduced several incompatibilities with 1.5.2,
|
||
such as single-argument append(), connect() and bind(), and changes to
|
||
str(long) and repr(float).
|
||
|
||
|
||
Binary Incompatibilities
|
||
------------------------
|
||
|
||
- Third party extensions built for Python 1.5.x or 1.6 cannot be used
|
||
with Python 2.0; these extensions will have to be rebuilt for Python
|
||
2.0.
|
||
|
||
- On Windows, attempting to import a third party extension built for
|
||
Python 1.5.x or 1.6 results in an immediate crash; there's not much we
|
||
can do about this. Check your PYTHONPATH environment variable!
|
||
|
||
- Python bytecode files (*.pyc and *.pyo) are not compatible between
|
||
releases.
|
||
|
||
|
||
Overview of Changes Since 1.6
|
||
-----------------------------
|
||
|
||
There are many new modules (including brand new XML support through
|
||
the xml package, and i18n support through the gettext module); a list
|
||
of all new modules is included below. Lots of bugs have been fixed.
|
||
|
||
The process for making major new changes to the language has changed
|
||
since Python 1.6. Enhancements must now be documented by a Python
|
||
Enhancement Proposal (PEP) before they can be accepted.
|
||
|
||
There are several important syntax enhancements, described in more
|
||
detail below:
|
||
|
||
- Augmented assignment, e.g. x += 1
|
||
|
||
- List comprehensions, e.g. [x**2 for x in range(10)]
|
||
|
||
- Extended import statement, e.g. import Module as Name
|
||
|
||
- Extended print statement, e.g. print >> file, "Hello"
|
||
|
||
Other important changes:
|
||
|
||
- Optional collection of cyclical garbage
|
||
|
||
Python Enhancement Proposal (PEP)
|
||
---------------------------------
|
||
|
||
PEP stands for Python Enhancement Proposal. A PEP is a design
|
||
document providing information to the Python community, or describing
|
||
a new feature for Python. The PEP should provide a concise technical
|
||
specification of the feature and a rationale for the feature.
|
||
|
||
We intend PEPs to be the primary mechanisms for proposing new
|
||
features, for collecting community input on an issue, and for
|
||
documenting the design decisions that have gone into Python. The PEP
|
||
author is responsible for building consensus within the community and
|
||
documenting dissenting opinions.
|
||
|
||
The PEPs are available at http://python.sourceforge.net/peps/.
|
||
|
||
Augmented Assignment
|
||
--------------------
|
||
|
||
This must have been the most-requested feature of the past years!
|
||
Eleven new assignment operators were added:
|
||
|
||
+= -= *= /= %= **= <<= >>= &= ^= |=
|
||
|
||
For example,
|
||
|
||
A += B
|
||
|
||
is similar to
|
||
|
||
A = A + B
|
||
|
||
except that A is evaluated only once (relevant when A is something
|
||
like dict[index].attr).
|
||
|
||
However, if A is a mutable object, A may be modified in place. Thus,
|
||
if A is a number or a string, A += B has the same effect as A = A+B
|
||
(except A is only evaluated once); but if a is a list, A += B has the
|
||
same effect as A.extend(B)!
|
||
|
||
Classes and built-in object types can override the new operators in
|
||
order to implement the in-place behavior; the not-in-place behavior is
|
||
used automatically as a fallback when an object doesn't implement the
|
||
in-place behavior. For classes, the method name is derived from the
|
||
method name for the corresponding not-in-place operator by inserting
|
||
an 'i' in front of the name, e.g. __iadd__ implements in-place
|
||
__add__.
|
||
|
||
Augmented assignment was implemented by Thomas Wouters.
|
||
|
||
|
||
List Comprehensions
|
||
-------------------
|
||
|
||
This is a flexible new notation for lists whose elements are computed
|
||
from another list (or lists). The simplest form is:
|
||
|
||
[<expression> for <variable> in <sequence>]
|
||
|
||
For example, [i**2 for i in range(4)] yields the list [0, 1, 4, 9].
|
||
This is more efficient than a for loop with a list.append() call.
|
||
|
||
You can also add a condition:
|
||
|
||
[<expression> for <variable> in <sequence> if <condition>]
|
||
|
||
For example, [w for w in words if w == w.lower()] would yield the list
|
||
of words that contain no uppercase characters. This is more efficient
|
||
than a for loop with an if statement and a list.append() call.
|
||
|
||
You can also have nested for loops and more than one 'if' clause. For
|
||
example, here's a function that flattens a sequence of sequences::
|
||
|
||
def flatten(seq):
|
||
return [x for subseq in seq for x in subseq]
|
||
|
||
flatten([[0], [1,2,3], [4,5], [6,7,8,9], []])
|
||
|
||
This prints
|
||
|
||
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
|
||
|
||
List comprehensions originated as a patch set from Greg Ewing; Skip
|
||
Montanaro and Thomas Wouters also contributed. Described by PEP 202.
|
||
|
||
|
||
Extended Import Statement
|
||
-------------------------
|
||
|
||
Many people have asked for a way to import a module under a different
|
||
name. This can be accomplished like this:
|
||
|
||
import foo
|
||
bar = foo
|
||
del foo
|
||
|
||
but this common idiom gets old quickly. A simple extension of the
|
||
import statement now allows this to be written as follows:
|
||
|
||
import foo as bar
|
||
|
||
There's also a variant for 'from ... import':
|
||
|
||
from foo import bar as spam
|
||
|
||
This also works with packages; e.g. you can write this:
|
||
|
||
import test.regrtest as regrtest
|
||
|
||
Note that 'as' is not a new keyword -- it is recognized only in this
|
||
context (this is only possible because the syntax for the import
|
||
statement doesn't involve expressions).
|
||
|
||
Implemented by Thomas Wouters. Described by PEP 221.
|
||
|
||
|
||
Extended Print Statement
|
||
------------------------
|
||
|
||
Easily the most controversial new feature, this extension to the print
|
||
statement adds an option to make the output go to a different file
|
||
than the default sys.stdout.
|
||
|
||
For example, to write an error message to sys.stderr, you can now
|
||
write:
|
||
|
||
print >> sys.stderr, "Error: bad dog!"
|
||
|
||
As a special feature, if the expression used to indicate the file
|
||
evaluates to None, the current value of sys.stdout is used. Thus:
|
||
|
||
print >> None, "Hello world"
|
||
|
||
is equivalent to
|
||
|
||
print "Hello world"
|
||
|
||
Design and implementation by Barry Warsaw. Described by PEP 214.
|
||
|
||
|
||
Optional Collection of Cyclical Garbage
|
||
---------------------------------------
|
||
|
||
Python is now equipped with a garbage collector that can hunt down
|
||
cyclical references between Python objects. It's no replacement for
|
||
reference counting; in fact, it depends on the reference counts being
|
||
correct, and decides that a set of objects belong to a cycle if all
|
||
their reference counts can be accounted for from their references to
|
||
each other. This devious scheme was first proposed by Eric Tiedemann,
|
||
and brought to implementation by Neil Schemenauer.
|
||
|
||
There's a module "gc" that lets you control some parameters of the
|
||
garbage collection. There's also an option to the configure script
|
||
that lets you enable or disable the garbage collection. In 2.0b1,
|
||
it's on by default, so that we (hopefully) can collect decent user
|
||
experience with this new feature. There are some questions about its
|
||
performance. If it proves to be too much of a problem, we'll turn it
|
||
off by default in the final 2.0 release.
|
||
|
||
|
||
Smaller Changes
|
||
---------------
|
||
|
||
A new function zip() was added. zip(seq1, seq2, ...) is equivalent to
|
||
map(None, seq1, seq2, ...) when the sequences have the same length;
|
||
i.e. zip([1,2,3], [10,20,30]) returns [(1,10), (2,20), (3,30)]. When
|
||
the lists are not all the same length, the shortest list wins:
|
||
zip([1,2,3], [10,20]) returns [(1,10), (2,20)]. See PEP 201.
|
||
|
||
sys.version_info is a tuple (major, minor, micro, level, serial).
|
||
|
||
Dictionaries have an odd new method, setdefault(key, default).
|
||
dict.setdefault(key, default) returns dict[key] if it exists; if not,
|
||
it sets dict[key] to default and returns that value. Thus:
|
||
|
||
dict.setdefault(key, []).append(item)
|
||
|
||
does the same work as this common idiom:
|
||
|
||
if not dict.has_key(key):
|
||
dict[key] = []
|
||
dict[key].append(item)
|
||
|
||
There are two new variants of SyntaxError that are raised for
|
||
indentation-related errors: IndentationError and TabError.
|
||
|
||
Changed \x to consume exactly two hex digits; see PEP 223. Added \U
|
||
escape that consumes exactly eight hex digits.
|
||
|
||
The limits on the size of expressions and file in Python source code
|
||
have been raised from 2**16 to 2**32. Previous versions of Python
|
||
were limited because the maximum argument size the Python VM accepted
|
||
was 2**16. This limited the size of object constructor expressions,
|
||
e.g. [1,2,3] or {'a':1, 'b':2}, and the size of source files. This
|
||
limit was raised thanks to a patch by Charles Waldman that effectively
|
||
fixes the problem. It is now much more likely that you will be
|
||
limited by available memory than by an arbitrary limit in Python.
|
||
|
||
The interpreter's maximum recursion depth can be modified by Python
|
||
programs using sys.getrecursionlimit and sys.setrecursionlimit. This
|
||
limit is the maximum number of recursive calls that can be made by
|
||
Python code. The limit exists to prevent infinite recursion from
|
||
overflowing the C stack and causing a core dump. The default value is
|
||
1000. The maximum safe value for a particular platform can be found
|
||
by running Misc/find_recursionlimit.py.
|
||
|
||
New Modules and Packages
|
||
------------------------
|
||
|
||
atexit - for registering functions to be called when Python exits.
|
||
|
||
imputil - Greg Stein's alternative API for writing custom import
|
||
hooks.
|
||
|
||
pyexpat - an interface to the Expat XML parser, contributed by Paul
|
||
Prescod.
|
||
|
||
xml - a new package with XML support code organized (so far) in three
|
||
subpackages: xml.dom, xml.sax, and xml.parsers. Describing these
|
||
would fill a volume. There's a special feature whereby a
|
||
user-installed package named _xmlplus overrides the standard
|
||
xmlpackage; this is intended to give the XML SIG a hook to distribute
|
||
backwards-compatible updates to the standard xml package.
|
||
|
||
webbrowser - a platform-independent API to launch a web browser.
|
||
|
||
|
||
Changed Modules
|
||
---------------
|
||
|
||
array -- new methods for array objects: count, extend, index, pop, and
|
||
remove
|
||
|
||
binascii -- new functions b2a_hex and a2b_hex that convert between
|
||
binary data and its hex representation
|
||
|
||
calendar -- Many new functions that support features including control
|
||
over which day of the week is the first day, returning strings instead
|
||
of printing them. Also new symbolic constants for days of week,
|
||
e.g. MONDAY, ..., SUNDAY.
|
||
|
||
cgi -- FieldStorage objects have a getvalue method that works like a
|
||
dictionary's get method and returns the value attribute of the object.
|
||
|
||
ConfigParser -- The parser object has new methods has_option,
|
||
remove_section, remove_option, set, and write. They allow the module
|
||
to be used for writing config files as well as reading them.
|
||
|
||
ftplib -- ntransfercmd(), transfercmd(), and retrbinary() all now
|
||
optionally support the RFC 959 REST command.
|
||
|
||
gzip -- readline and readlines now accept optional size arguments
|
||
|
||
httplib -- New interfaces and support for HTTP/1.1 by Greg Stein. See
|
||
the module doc strings for details.
|
||
|
||
locale -- implement getdefaultlocale for Win32 and Macintosh
|
||
|
||
marshal -- no longer dumps core when marshaling deeply nested or
|
||
recursive data structures
|
||
|
||
os -- new functions isatty, seteuid, setegid, setreuid, setregid
|
||
|
||
os/popen2 -- popen2/popen3/popen4 support under Windows. popen2/popen3
|
||
support under Unix.
|
||
|
||
os/pty -- support for openpty and forkpty
|
||
|
||
os.path -- fix semantics of os.path.commonprefix
|
||
|
||
smtplib -- support for sending very long messages
|
||
|
||
socket -- new function getfqdn()
|
||
|
||
readline -- new functions to read, write and truncate history files.
|
||
The readline section of the library reference manual contains an
|
||
example.
|
||
|
||
select -- add interface to poll system call
|
||
|
||
shutil -- new copyfileobj function
|
||
|
||
SimpleHTTPServer, CGIHTTPServer -- Fix problems with buffering in the
|
||
HTTP server.
|
||
|
||
Tkinter -- optimization of function flatten
|
||
|
||
urllib -- scans environment variables for proxy configuration,
|
||
e.g. http_proxy.
|
||
|
||
whichdb -- recognizes dumbdbm format
|
||
|
||
|
||
Obsolete Modules
|
||
----------------
|
||
|
||
None. However note that 1.6 made a whole slew of modules obsolete:
|
||
stdwin, soundex, cml, cmpcache, dircache, dump, find, grep, packmail,
|
||
poly, zmod, strop, util, whatsound.
|
||
|
||
|
||
Changed, New, Obsolete Tools
|
||
----------------------------
|
||
|
||
None.
|
||
|
||
|
||
C-level Changes
|
||
---------------
|
||
|
||
Several cleanup jobs were carried out throughout the source code.
|
||
|
||
All C code was converted to ANSI C; we got rid of all uses of the
|
||
Py_PROTO() macro, which makes the header files a lot more readable.
|
||
|
||
Most of the portability hacks were moved to a new header file,
|
||
pyport.h; several other new header files were added and some old
|
||
header files were removed, in an attempt to create a more rational set
|
||
of header files. (Few of these ever need to be included explicitly;
|
||
they are all included by Python.h.)
|
||
|
||
Trent Mick ensured portability to 64-bit platforms, under both Linux
|
||
and Win64, especially for the new Intel Itanium processor. Mick also
|
||
added large file support for Linux64 and Win64.
|
||
|
||
The C APIs to return an object's size have been update to consistently
|
||
use the form PyXXX_Size, e.g. PySequence_Size and PyDict_Size. In
|
||
previous versions, the abstract interfaces used PyXXX_Length and the
|
||
concrete interfaces used PyXXX_Size. The old names,
|
||
e.g. PyObject_Length, are still available for backwards compatibility
|
||
at the API level, but are deprecated.
|
||
|
||
The PyOS_CheckStack function has been implemented on Windows by
|
||
Fredrik Lundh. It prevents Python from failing with a stack overflow
|
||
on Windows.
|
||
|
||
The GC changes resulted in creation of two new slots on object,
|
||
tp_traverse and tp_clear. The augmented assignment changes result in
|
||
the creation of a new slot for each in-place operator.
|
||
|
||
The GC API creates new requirements for container types implemented in
|
||
C extension modules. See Include/objimpl.h for details.
|
||
|
||
PyErr_Format has been updated to automatically calculate the size of
|
||
the buffer needed to hold the formatted result string. This change
|
||
prevents crashes caused by programmer error.
|
||
|
||
New C API calls: PyObject_AsFileDescriptor, PyErr_WriteUnraisable.
|
||
|
||
PyRun_AnyFileEx, PyRun_SimpleFileEx, PyRun_FileEx -- New functions
|
||
that are the same as their non-Ex counterparts except they take an
|
||
extra flag argument that tells them to close the file when done.
|
||
|
||
XXX There were other API changes that should be fleshed out here.
|
||
|
||
|
||
Windows Changes
|
||
---------------
|
||
|
||
New popen2/popen3/peopen4 in os module (see Changed Modules above).
|
||
|
||
os.popen is much more usable on Windows 95 and 98. See Microsoft
|
||
Knowledge Base article Q150956. The Win9x workaround described there
|
||
is implemented by the new w9xpopen.exe helper in the root of your
|
||
Python installation. Note that Python uses this internally; it is not
|
||
a standalone program.
|
||
|
||
Administrator privileges are no longer required to install Python
|
||
on Windows NT or Windows 2000. If you have administrator privileges,
|
||
Python's registry info will be written under HKEY_LOCAL_MACHINE.
|
||
Otherwise the installer backs off to writing Python's registry info
|
||
under HKEY_CURRENT_USER. The latter is sufficient for all "normal"
|
||
uses of Python, but will prevent some advanced uses from working
|
||
(for example, running a Python script as an NT service, or possibly
|
||
from CGI).
|
||
|
||
[This was new in 1.6] The installer no longer runs a separate Tcl/Tk
|
||
installer; instead, it installs the needed Tcl/Tk files directly in the
|
||
Python directory. If you already have a Tcl/Tk installation, this
|
||
wastes some disk space (about 4 Megs) but avoids problems with
|
||
conflicting Tcl/Tk installations, and makes it much easier for Python
|
||
to ensure that Tcl/Tk can find all its files.
|
||
|
||
[This was new in 1.6] The Windows installer now installs by default in
|
||
\Python20\ on the default volume, instead of \Program Files\Python-2.0\.
|
||
|
||
|
||
Updates to the changes between 1.5.2 and 1.6
|
||
--------------------------------------------
|
||
|
||
The 1.6 NEWS file can't be changed after the release is done, so here
|
||
is some late-breaking news:
|
||
|
||
New APIs in locale.py: normalize(), getdefaultlocale(), resetlocale(),
|
||
and changes to getlocale() and setlocale().
|
||
|
||
The new module is now enabled per default.
|
||
|
||
It is not true that the encodings codecs cannot be used for normal
|
||
strings: the string.encode() (which is also present on 8-bit strings
|
||
!) allows using them for 8-bit strings too, e.g. to convert files from
|
||
cp1252 (Windows) to latin-1 or vice-versa.
|
||
|
||
Japanese codecs are available from Tamito KAJIYAMA:
|
||
http://pseudo.grad.sccs.chukyo-u.ac.jp/~kajiyama/python/
|
||
|
||
|
||
======================================================================
|