Mirror
/
cpython
mirror of https://github.com/python/cpython
4
1
Fork 0
Code Issues Releases Wiki Activity

Synced builtin open and io.open documentation, taking the best of each

This commit is contained in:
Benjamin Peterson 2008-04-11 21:17:32 +00:00
parent d12fbe9ef7
commit dd21912cd0
2 changed files with 114 additions and 95 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

139
Doc/library/functions.rst
View File

@ -698,94 +698,89 @@ available. They are listed here in alphabetical order.
:meth:`__index__` method that returns an integer. :meth:`__index__` method that returns an integer.
.. function:: open(filename[, mode='r'[, buffering=None[, encoding=None[, errors=None[, newline=None[, closefd=True]]]]]]) .. function:: open(file[, mode='r'[, buffering=None[, encoding=None[, errors=None[, newline=None[, closefd=True]]]]]])
Open a file, returning an object of the :class:`file` type described in Open a file. If the file cannot be opened, :exc:`IOError` is raised.
section :ref:`bltin-file-objects`. If the file cannot be opened,
:exc:`IOError` is raised. When opening a file, it's preferable to use
:func:`open` instead of invoking the :class:`file` constructor directly.
*filename* is either a string giving the name (and the path if the *file* is either a string giving the name (and the path if the file isn't in
file isn't in the current working directory) of the file to be the current working directory) of the file to be opened or an integer file
opened; or an integer file descriptor of the file to be wrapped. (If descriptor of the file to be wrapped. (If a file descriptor is given, it is
a file descriptor is given, it is closed when the returned I/O object closed when the returned I/O object is closed, unless *closefd* is set to
is closed, unless *closefd* is set to ``False``.) ``False``.)
*mode* is an optional string that specifies the mode in which the file is *mode* is an optional string that specifies the mode in which the file is
opened. It defaults to ``'r'`` which means open for reading in text mode. opened. It defaults to ``'r'`` which means open for reading in text mode.
Other common values are ``'w'`` for writing (truncating the file if Other common values are ``'w'`` for writing (truncating the file if it
it already exists), and ``'a'`` for appending (which on *some* Unix already exists), and ``'a'`` for appending (which on *some* Unix systems,
systems means that *all* writes append to the end of the file means that *all* writes append to the end of the file regardless of the
regardless of the current seek position). In text mode, if *encoding* current seek position). In text mode, if *encoding* is not specified the
is not specified the encoding used is platform dependent. (For reading encoding used is platform dependent. (For reading and writing raw bytes use
and writing raw bytes use binary mode and leave *encoding* binary mode and leave *encoding* unspecified.) The available modes are:
unspecified.) The available modes are:
* 'r' open for reading (default) ========= ===============================================================
* 'w' open for writing, truncating the file first Character Meaning
* 'a' open for writing, appending to the end if the file exists --------- ---------------------------------------------------------------
* 'b' binary mode ``'r'`` open for reading (default)
* 't' text mode (default) ``'w'`` open for writing, truncating the file first
* '+' open the file for updating (implies both reading and writing) ``'a'`` open for writing, appending to the end of the file if it exists
* 'U' universal newline mode (for backwards compatibility; ``'b'`` binary mode
unnecessary in new code) ``'t'`` text mode (default)
``'+'`` open a disk file for updating (reading and writing)
``'U'`` universal newline mode (for backwards compatibility; unneeded
for new code)
========= ===============================================================
The most commonly-used values of *mode* are ``'r'`` for reading, ``'w'`` for The default mode is ``'rt'`` (open for reading text). For binary random
writing (truncating the file if it already exists), and ``'a'`` for appending access, the mode ``'w+b'`` opens and truncates the file to 0 bytes, while
(which on *some* Unix systems means that *all* writes append to the end of the ``'r+b'`` opens the file without truncation.
file regardless of the current seek position). If *mode* is omitted, it
defaults to ``'r'``. The default is to use text mode, which may convert
``'\n'`` characters to a platform-specific representation on writing and back
on reading. Thus, when opening a binary file, you should append ``'b'`` to
the *mode* value to open the file in binary mode, which will improve
portability. (Appending ``'b'`` is useful even on systems that don't treat
binary and text files differently, where it serves as documentation.) See below
for more possible values of *mode*.
Python distinguishes between files opened in binary and text modes, even Python distinguishes between files opened in binary and text modes, even
when the underlying operating system doesn't. Files opened in binary when the underlying operating system doesn't. Files opened in binary
mode (appending ``'b'`` to the *mode* argument) return contents as mode (appending ``'b'`` to the *mode* argument) return contents as
``bytes`` objects without any decoding. In text mode (the default, ``bytes`` objects without any decoding. In text mode (the default, or when
or when ``'t'`` is appended to the *mode* argument) the contents of ``'t'`` is appended to the *mode* argument) the contents of
the file are returned as strings, the bytes having been first decoded the file are returned as strings, the bytes having been first decoded
using a platform-dependent encoding or using the specified *encoding* using a platform-dependent encoding or using the specified *encoding*
if given. if given.
*buffering* is an optional integer used to set the buffering policy. By *buffering* is an optional integer used to set the buffering policy. By
default full buffering is on. Pass 0 to switch buffering off (only default full buffering is on. Pass 0 to switch buffering off (only allowed in
allowed in binary mode), 1 to set line buffering, and an integer > 1 binary mode), 1 to set line buffering, and an integer > 1 for full buffering.
for full buffering.
*encoding* is an optional string that specifies the file's encoding when *encoding* is the name of the encoding used to decode or encode the file.
reading or writing in text mode---this argument should not be used in This should only be used in text mode. The default encoding is platform
binary mode. The default encoding is platform dependent, but any encoding dependent, but any encoding supported by Python can be passed. See the
supported by Python can be used. (See the :mod:`codecs` module for :mod:`codecs` module for the list of supported encodings.
the list of supported encodings.)
*errors* is an optional string that specifies how encoding errors are to be *errors* is an optional string that specifies how encoding errors are to be
handled---this argument should not be used in binary mode. Pass handled---this argument should not be used in binary mode. Pass ``'strict'``
``'strict'`` to raise a :exc:`ValueError` exception if there is an encoding to raise a :exc:`ValueError` exception if there is an encoding error (the
error (the default of ``None`` has the same effect), or pass ``'ignore'`` default of ``None`` has the same effect), or pass ``'ignore'`` to ignore
to ignore errors. (Note that ignoring encoding errors can lead to errors. (Note that ignoring encoding errors can lead to data loss.) See the
data loss.) See the documentation for :func:`codecs.register` for a documentation for :func:`codecs.register` for a list of the permitted
list of the permitted encoding error strings. encoding error strings.
*newline* is an optional string that specifies the newline character(s). *newline* controls how universal newlines works (it only applies to text
When reading, if *newline* is ``None``, universal newlines mode is enabled. mode). It can be ``None``, ``''``, ``'\n'``, ``'\r'``, and ``'\r\n'``. It
Lines read in univeral newlines mode can end in ``'\n'``, ``'\r'``, works as follows:
or ``'\r\n'``, and these are translated into ``'\n'``. If *newline*
is ``''``, universal newline mode is enabled, but line endings are
not translated. If any other string is given, lines are assumed to be
terminated by that string, and no translating is done. When writing,
if *newline* is ``None``, any ``'\n'`` characters written are
translated to the system default line separator, :attr:`os.linesep`.
If *newline* is ``''``, no translation takes place. If *newline* is
any of the other standard values, any ``'\n'`` characters written are
translated to the given string.
*closefd* is an optional Boolean which specifies whether to keep the * On input, if *newline* is ``None``, universal newlines mode is enabled.
underlying file descriptor open. It must be ``True`` (the default) if Lines in the input can end in ``'\n'``, ``'\r'``, or ``'\r\n'``, and these
a filename is given. are translated into ``'\n'`` before being returned to the caller. If it is
``''``, universal newline mode is enabled, but line endings are returned to
the caller untranslated. If it has any of the other legal values, input
lines are only terminated by the given string, and the line ending is
returned to the caller untranslated.
* On output, if *newline* is ``None``, any ``'\n'`` characters written are
translated to the system default line separator, :data:`os.linesep`. If
*newline* is ``''``, no translation takes place. If *newline* is any of
the other legal values, any ``'\n'`` characters written are translated to
the given string.
If *closefd* is ``False``, the underlying file descriptor will be kept open
when the file is closed. This does not work when a file name is given and
must be ``True`` in that case.
.. index:: .. index::
single: line-buffered I/O single: line-buffered I/O
@ -796,9 +791,9 @@ available. They are listed here in alphabetical order.
single: text mode single: text mode
module: sys module: sys
See also the file handling modules, such as, See also the file handling modules, such as, :mod:`fileinput`, :mod:`io`
:mod:`fileinput`, :mod:`os`, :mod:`os.path`, :mod:`tempfile`, and (where :func:`open()` is declared), :mod:`os`, :mod:`os.path`,
:mod:`shutil`. :mod:`tempfile`, and :mod:`shutil`.
.. XXX works for bytes too, but should it? .. XXX works for bytes too, but should it?

70
Doc/library/io.rst
View File

@ -44,13 +44,23 @@ Module Interface
.. function:: open(file[, mode[, buffering[, encoding[, errors[, newline[, closefd=True]]]]]]) .. function:: open(file[, mode[, buffering[, encoding[, errors[, newline[, closefd=True]]]]]])
Open *file* and return a stream. Open *file* and return a stream. If the file cannot be opened, an
:exc:`IOError` is raised.
*file* is a string giving the name of the file, or an integer file descriptor *file* is either a string giving the name (and the path if the file isn't in
of the file to be wrapped. the current working directory) of the file to be opened or an integer file
descriptor of the file to be wrapped. (If a file descriptor is given, it is
closed when the returned I/O object is closed, unless *closefd* is set to
``False``.)
The optional *mode* string determines how the file is opened and consists of *mode* is an optional string that specifies the mode in which the file is
a combination of the following characters: opened. It defaults to ``'r'`` which means open for reading in text mode.
Other common values are ``'w'`` for writing (truncating the file if it
already exists), and ``'a'`` for appending (which on *some* Unix systems,
means that *all* writes append to the end of the file regardless of the
current seek position). In text mode, if *encoding* is not specified the
encoding used is platform dependent. (For reading and writing raw bytes use
binary mode and leave *encoding* unspecified.) The available modes are:
========= =============================================================== ========= ===============================================================
Character Meaning Character Meaning
@ -69,18 +79,31 @@ Module Interface
access, the mode ``'w+b'`` opens and truncates the file to 0 bytes, while access, the mode ``'w+b'`` opens and truncates the file to 0 bytes, while
``'r+b'`` opens the file without truncation. ``'r+b'`` opens the file without truncation.
*buffering* is an optional argument controling the buffering of the returned Python distinguishes between files opened in binary and text modes, even
stream. A value of ``0`` means no buffering, ``1`` means line buffered, and when the underlying operating system doesn't. Files opened in binary
a greater value means full buffering with the given buffer size. Buffering mode (appending ``'b'`` to the *mode* argument) return contents as
cannot be disabled in text mode. ``bytes`` objects without any decoding. In text mode (the default, or when
``'t'`` is appended to the *mode* argument) the contents of
the file are returned as strings, the bytes having been first decoded
using a platform-dependent encoding or using the specified *encoding*
if given.
*buffering* is an optional integer used to set the buffering policy. By
default full buffering is on. Pass 0 to switch buffering off (only allowed in
binary mode), 1 to set line buffering, and an integer > 1 for full buffering.
*encoding* is the name of the encoding used to decode or encode the file. *encoding* is the name of the encoding used to decode or encode the file.
This may only be used in text mode. Any encoding available in the This should only be used in text mode. The default encoding is platform
:mod:`codecs` module registry can be used. dependent, but any encoding supported by Python can be passed. See the
:mod:`codecs` module for the list of supported encodings.
*errors* specifies how the encoding should treat errors. "strict", the *errors* is an optional string that specifies how encoding errors are to be
default raises a :exc:`ValueError` on problems. See the *errors* argument handled---this argument should not be used in binary mode. Pass ``'strict'``
of :func:`codecs.open` for more information. XXX to raise a :exc:`ValueError` exception if there is an encoding error (the
default of ``None`` has the same effect), or pass ``'ignore'`` to ignore
errors. (Note that ignoring encoding errors can lead to data loss.) See the
documentation for :func:`codecs.register` for a list of the permitted
encoding error strings.
*newline* controls how universal newlines works (it only applies to text *newline* controls how universal newlines works (it only applies to text
mode). It can be ``None``, ``''``, ``'\n'``, ``'\r'``, and ``'\r\n'``. It mode). It can be ``None``, ``''``, ``'\n'``, ``'\r'``, and ``'\r\n'``. It
@ -100,13 +123,14 @@ Module Interface
the other legal values, any ``'\n'`` characters written are translated to the other legal values, any ``'\n'`` characters written are translated to
the given string. the given string.
If *closefd* is :keyword:`False`, the underlying file descriptor will be kept If *closefd* is ``False``, the underlying file descriptor will be kept open
open when the file is closed. This does not work when a file name is given. when the file is closed. This does not work when a file name is given and
must be ``True`` in that case.
The :func:`open` function returns a file object whose type depends on the :func:`open()` returns a file object whose type depends on the mode, and
mode, and through which the standard file operations such as reading and through which the standard file operations such as reading and writing are
writing are performed. When :func:`open` is used to open a file in a text performed. When :func:`open()` is used to open a file in a text mode
mode (``'w'``, ``'r'``, ``'wt'``, ``'rt'``, etc.), it returns a (``'w'``, ``'r'``, ``'wt'``, ``'rt'``, etc.), it returns a
:class:`TextIOWrapper`. When used to open a file in a binary mode, the :class:`TextIOWrapper`. When used to open a file in a binary mode, the
returned class varies: in read binary mode, it returns a returned class varies: in read binary mode, it returns a
:class:`BufferedReader`; in write binary and append binary modes, it returns :class:`BufferedReader`; in write binary and append binary modes, it returns
@ -114,9 +138,9 @@ Module Interface
:class:`BufferedRandom`. :class:`BufferedRandom`.
It is also possible to use a string or bytearray as a file for both reading It is also possible to use a string or bytearray as a file for both reading
and writing. For strings :class:`io.StringIO` can be used like a file opened and writing. For strings :class:`StringIO` can be used like a file opened in
in a text mode, and for bytes a :class:`io.BytesIO` can be used like a file a text mode, and for bytes a :class:`BytesIO` can be used like a file opened
opened in a binary mode. in a binary mode.
.. exception:: BlockingIOError .. exception:: BlockingIOError