lseek() always returns 0 for character pseudo-devices like
`/dev/urandom` (for other non-regular files, e.g. `/dev/stdin`, it
always returns -1, to which CPython reacts by raising appropriate
exceptions). They are thus technically seekable despite not having seek
semantics.
When calling read() on e.g. an instance of `io.BufferedReader` that
wraps such a file, `BufferedReader` reads ahead, filling its buffer,
creating a discrepancy between the number of bytes read and the internal
`tell()` always returning 0, which previously resulted in e.g.
`BufferedReader.tell()` or `BufferedReader.seek()` being able to return
positions < 0 even though these are supposed to be always >= 0.
Invariably keep the return value non-negative by returning
max(former_return_value, 0) instead, and add some corresponding tests.
Remove io.OpenWrapper and _pyio.OpenWrapper, deprecated in Python
3.10: just use :func:`open` instead. The open() (io.open()) function
is a built-in function. Since Python 3.10, _pyio.open() is also a
static method.
`TextIOWrapper.__init__()` called `os.device_encoding(file.fileno())` if fileno is 0-2 and encoding=None.
But it is very rarely works, and never documented behavior.
open(), io.open(), codecs.open() and fileinput.FileInput no longer
accept "U" ("universal newline") in the file mode. This flag was
deprecated since Python 3.3.
Deprecate io.OpenWrapper and _pyio.OpenWrapper: use io.open and
_pyio.open instead. Until Python 3.9, _pyio.open was not a static
method and builtins.open was set to OpenWrapper to not become a bound
method when set to a class variable. _io.open is a built-in function
whereas _pyio.open is a Python function. In Python 3.10, _pyio.open()
is now a static method, and builtins.open() is now io.open().
The Python _pyio.open() function becomes a static method to behave as
io.open() built-in function: don't become a bound method when stored
as a class variable. It becomes possible since static methods are now
callable in Python 3.10. Moreover, _pyio.OpenWrapper becomes a simple
alias to _pyio.open.
init_set_builtins_open() now sets builtins.open to io.open, rather
than setting it to io.OpenWrapper, since OpenWrapper is now an alias
to open in the io and _pyio modules.
See [PEP 597](https://www.python.org/dev/peps/pep-0597/).
* Add `-X warn_default_encoding` and `PYTHONWARNDEFAULTENCODING`.
* Add EncodingWarning
* Add io.text_encoding()
* open(), TextIOWrapper() emits EncodingWarning when encoding is omitted and warn_default_encoding is enabled.
* _pyio.TextIOWrapper() uses UTF-8 as fallback default encoding used when failed to import locale module. (used during building Python)
* bz2, configparser, gzip, lzma, pathlib, tempfile modules use io.text_encoding().
* What's new entry
The truncate() method of io.BufferedReader() should raise
UnsupportedOperation when it is called on a read-only
io.BufferedReader() instance.
https://bugs.python.org/issue35950
Automerge-Triggered-By: @methane
open(), io.open(), codecs.open() and fileinput.FileInput no longer
accept "U" ("universal newline") in the file mode. This flag was
deprecated since Python 3.3.
* Use the 'p' format unit instead of manually called PyObject_IsTrue().
* Pass boolean value instead 0/1 integers to functions that needs boolean.
* Convert some arguments to boolean only once.
In development mode and in debug build, encoding and errors arguments
are now checked on string encoding and decoding operations. Examples:
open(), str.encode() and bytes.decode().
By default, for best performances, the errors argument is only
checked at the first encoding/decoding error, and the encoding
argument is sometimes ignored for empty strings.
Fix destructor _pyio.BytesIO and _pyio.TextIOWrapper: initialize
their _buffer attribute as soon as possible (in the class body),
because it's used by __del__() which calls close().
In development (-X dev) mode and in a debug build, IOBase finalizer
of the _pyio module now logs the exception if the close() method
fails. The exception is ignored silently by default in release build.
test_io: test_error_through_destructor() now uses
support.catch_unraisable_exception() rather than capturing stderr.
Move all documentation regarding the readinto method into either io.RawIOBase or io.BufferedIOBase.
Corresponding changes to documentation in the _pyio.py module.
The previous code hardcoded `SEEK_SET`, etc. While it's very unlikely
that these values will change, it's best to use the definitions to avoid
there being mismatches in behavior with the code in the future.
Signed-off-by: Enji Cooper <yaneurabeya@gmail.com>
If buffering=1 is specified for open() in binary mode, it is silently
treated as buffering=-1 (i.e., the default buffer size).
Coupled with the fact that line buffering is always supported in Python 2,
such behavior caused several issues (e.g., bpo-10344, bpo-21332).
Warn that line buffering is not supported if open() is called with
binary mode and buffering=1.
* Maintain a list of BufferedWriter objects. Flush them on exit.
In Python 3, the buffer and the underlying file object are separate
and so the order in which objects are finalized matters. This is
unlike Python 2 where the file and buffer were a single object and
finalization was done for both at the same time. In Python 3, if
the file is finalized and closed before the buffer then the data in
the buffer is lost.
This change adds a doubly linked list of open file buffers. An atexit
hook ensures they are flushed before proceeding with interpreter
shutdown. This is addition does not remove the need to properly close
files as there are other reasons why buffered data could get lost during
finalization.
Initial patch by Armin Rigo.
* Use weakref.WeakSet instead of WeakKeyDictionary.
* Simplify buffered double-linked list types.
* In _flush_all_writers(), suppress errors from flush().
* Remove NEWS entry, use blurb.
* Take more care when flushing file buffers from atexit.
The previous implementation was not careful enough to avoid
causing issues in multi-threaded cases. Check for buf->ok
and buf->finalizing before actually doing the flush. Also,
increase the refcnt to ensure the object does not disappear.
* Maintain a list of BufferedWriter objects. Flush them on exit.
In Python 3, the buffer and the underlying file object are separate
and so the order in which objects are finalized matters. This is
unlike Python 2 where the file and buffer were a single object and
finalization was done for both at the same time. In Python 3, if
the file is finalized and closed before the buffer then the data in
the buffer is lost.
This change adds a doubly linked list of open file buffers. An atexit
hook ensures they are flushed before proceeding with interpreter
shutdown. This is addition does not remove the need to properly close
files as there are other reasons why buffered data could get lost during
finalization.
Initial patch by Armin Rigo.
* Use weakref.WeakSet instead of WeakKeyDictionary.
* Simplify buffered double-linked list types.
* In _flush_all_writers(), suppress errors from flush().
* Remove NEWS entry, use blurb.
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