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Andrew M. Kuchling 2008-04-08 21:22:53 +00:00
parent 775e10d9e6
commit abf8e015c2
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@ -746,7 +746,70 @@ XXX give example
PEP 3116: New I/O Library
=====================================================
XXX write this.
Python's built-in file objects support a number of methods, but
file-like objects don't necessarily support all of them. Objects that
imitate files usually support :meth:`read` and :meth:`write`, but they
may not support :meth:`readline`. Python 3.0 introduces a layered I/O
library in the :mod:`io` module that separates buffering and
text-handling features from the fundamental read and write operations.
There are three levels of abstract base classes provided by
the :mod:`io` module:
* :class:`RawIOBase`: defines raw I/O operations: :meth:`read`,
:meth:`readinto`,
:meth:`write`, :meth:`seek`, :meth:`tell`, :meth:`truncate`,
and :meth:`close`.
Most of the methods of this class will often map to a single system call.
There are also :meth:`readable`, :meth:`writable`, and :meth:`seekable`
methods for determining what operations a given object will allow.
Python 3.0 has concrete implementations of this class for files and
sockets, but Python 2.6 hasn't restructured its file and socket objects
in this way.
.. XXX should 2.6 register them in io.py?
* :class:`BufferedIOBase`: is an abstract base class that
buffers data in memory to reduce the number of
system calls used, making I/O processing more efficient.
It supports all of the methods of :class:`RawIOBase`,
and adds a :attr:`raw` attribute holding the underlying raw object.
There are four concrete classes implementing this ABC:
:class:`BufferedWriter` and
:class:`BufferedReader` for objects that only support
writing or reading and don't support random access,
:class:`BufferedRandom` for objects that support the :meth:`seek` method
for random access,
and :class:`BufferedRWPair` for objects such as TTYs that have
both read and write operations that act upon unconnected streams of data.
* :class:`TextIOBase`: Provides functions for reading and writing
strings (remember, strings will be Unicode in Python 3.0),
and supporting universal newlines. :class:`TextIOBase` defines
the :meth:`readline` method and supports iteration upon
objects.
There are two concrete implementations. :class:`TextIOWrapper`
wraps a buffered I/O object, supporting all of the methods for
text I/O and adding a :attr:`buffer` attribute for access
to the underlying object. :class:`StringIO` simply buffers
everything in memory without ever writing anything to disk.
(In current 2.6 alpha releases, :class:`io.StringIO` is implemented in
pure Python, so it's pretty slow. You should therefore stick with the
existing :mod:`StringIO` module or :mod:`cStringIO` for now. At some
point Python 3.0's :mod:`io` module will be rewritten into C for speed,
and perhaps the C implementation will be backported to the 2.x releases.)
.. XXX check before final release: is io.py still written in Python?
In Python 2.6, the underlying implementations haven't been
restructured to build on top of the :mod:`io` module's classes. The
module is being provided to make it easier to write code that's
forward-compatible with 3.0, and to save developers the effort of writing
their own implementations of buffering and text I/O.
.. seealso::
@ -1571,7 +1634,7 @@ complete list of changes, or look through the CVS logs for all the details.
(3, 1), (3, 2), (3, 4),
(4, 1), (4, 2), (4, 3)]
``itertools.chain(*iterables)` is an existing function in
``itertools.chain(*iterables)`` is an existing function in
:mod:`itertools` that gained a new constructor in Python 2.6.
``itertools.chain.from_iterable(iterable)`` takes a single
iterable that should return other iterables. :func:`chain` will