208 lines
7.9 KiB
ReStructuredText
208 lines
7.9 KiB
ReStructuredText
:mod:`fileinput` --- Iterate over lines from multiple input streams
|
|
===================================================================
|
|
|
|
.. module:: fileinput
|
|
:synopsis: Loop over standard input or a list of files.
|
|
|
|
.. moduleauthor:: Guido van Rossum <guido@python.org>
|
|
.. sectionauthor:: Fred L. Drake, Jr. <fdrake@acm.org>
|
|
|
|
**Source code:** :source:`Lib/fileinput.py`
|
|
|
|
--------------
|
|
|
|
This module implements a helper class and functions to quickly write a
|
|
loop over standard input or a list of files. If you just want to read or
|
|
write one file see :func:`open`.
|
|
|
|
The typical use is::
|
|
|
|
import fileinput
|
|
for line in fileinput.input():
|
|
process(line)
|
|
|
|
This iterates over the lines of all files listed in ``sys.argv[1:]``, defaulting
|
|
to ``sys.stdin`` if the list is empty. If a filename is ``'-'``, it is also
|
|
replaced by ``sys.stdin``. To specify an alternative list of filenames, pass it
|
|
as the first argument to :func:`.input`. A single file name is also allowed.
|
|
|
|
All files are opened in text mode by default, but you can override this by
|
|
specifying the *mode* parameter in the call to :func:`.input` or
|
|
:class:`FileInput`. If an I/O error occurs during opening or reading a file,
|
|
:exc:`OSError` is raised.
|
|
|
|
.. versionchanged:: 3.3
|
|
:exc:`IOError` used to be raised; it is now an alias of :exc:`OSError`.
|
|
|
|
If ``sys.stdin`` is used more than once, the second and further use will return
|
|
no lines, except perhaps for interactive use, or if it has been explicitly reset
|
|
(e.g. using ``sys.stdin.seek(0)``).
|
|
|
|
Empty files are opened and immediately closed; the only time their presence in
|
|
the list of filenames is noticeable at all is when the last file opened is
|
|
empty.
|
|
|
|
Lines are returned with any newlines intact, which means that the last line in
|
|
a file may not have one.
|
|
|
|
You can control how files are opened by providing an opening hook via the
|
|
*openhook* parameter to :func:`fileinput.input` or :class:`FileInput()`. The
|
|
hook must be a function that takes two arguments, *filename* and *mode*, and
|
|
returns an accordingly opened file-like object. Two useful hooks are already
|
|
provided by this module.
|
|
|
|
The following function is the primary interface of this module:
|
|
|
|
|
|
.. function:: input(files=None, inplace=False, backup='', bufsize=0, mode='r', openhook=None)
|
|
|
|
Create an instance of the :class:`FileInput` class. The instance will be used
|
|
as global state for the functions of this module, and is also returned to use
|
|
during iteration. The parameters to this function will be passed along to the
|
|
constructor of the :class:`FileInput` class.
|
|
|
|
The :class:`FileInput` instance can be used as a context manager in the
|
|
:keyword:`with` statement. In this example, *input* is closed after the
|
|
:keyword:`!with` statement is exited, even if an exception occurs::
|
|
|
|
with fileinput.input(files=('spam.txt', 'eggs.txt')) as f:
|
|
for line in f:
|
|
process(line)
|
|
|
|
.. versionchanged:: 3.2
|
|
Can be used as a context manager.
|
|
|
|
.. deprecated-removed:: 3.6 3.8
|
|
The *bufsize* parameter.
|
|
|
|
The following functions use the global state created by :func:`fileinput.input`;
|
|
if there is no active state, :exc:`RuntimeError` is raised.
|
|
|
|
|
|
.. function:: filename()
|
|
|
|
Return the name of the file currently being read. Before the first line has
|
|
been read, returns ``None``.
|
|
|
|
|
|
.. function:: fileno()
|
|
|
|
Return the integer "file descriptor" for the current file. When no file is
|
|
opened (before the first line and between files), returns ``-1``.
|
|
|
|
|
|
.. function:: lineno()
|
|
|
|
Return the cumulative line number of the line that has just been read. Before
|
|
the first line has been read, returns ``0``. After the last line of the last
|
|
file has been read, returns the line number of that line.
|
|
|
|
|
|
.. function:: filelineno()
|
|
|
|
Return the line number in the current file. Before the first line has been
|
|
read, returns ``0``. After the last line of the last file has been read,
|
|
returns the line number of that line within the file.
|
|
|
|
|
|
.. function:: isfirstline()
|
|
|
|
Returns true if the line just read is the first line of its file, otherwise
|
|
returns false.
|
|
|
|
|
|
.. function:: isstdin()
|
|
|
|
Returns true if the last line was read from ``sys.stdin``, otherwise returns
|
|
false.
|
|
|
|
|
|
.. function:: nextfile()
|
|
|
|
Close the current file so that the next iteration will read the first line from
|
|
the next file (if any); lines not read from the file will not count towards the
|
|
cumulative line count. The filename is not changed until after the first line
|
|
of the next file has been read. Before the first line has been read, this
|
|
function has no effect; it cannot be used to skip the first file. After the
|
|
last line of the last file has been read, this function has no effect.
|
|
|
|
|
|
.. function:: close()
|
|
|
|
Close the sequence.
|
|
|
|
The class which implements the sequence behavior provided by the module is
|
|
available for subclassing as well:
|
|
|
|
|
|
.. class:: FileInput(files=None, inplace=False, backup='', bufsize=0, mode='r', openhook=None)
|
|
|
|
Class :class:`FileInput` is the implementation; its methods :meth:`filename`,
|
|
:meth:`fileno`, :meth:`lineno`, :meth:`filelineno`, :meth:`isfirstline`,
|
|
:meth:`isstdin`, :meth:`nextfile` and :meth:`close` correspond to the
|
|
functions of the same name in the module. In addition it has a
|
|
:meth:`~io.TextIOBase.readline` method which returns the next input line,
|
|
and a :meth:`__getitem__` method which implements the sequence behavior.
|
|
The sequence must be accessed in strictly sequential order; random access
|
|
and :meth:`~io.TextIOBase.readline` cannot be mixed.
|
|
|
|
With *mode* you can specify which file mode will be passed to :func:`open`. It
|
|
must be one of ``'r'``, ``'rU'``, ``'U'`` and ``'rb'``.
|
|
|
|
The *openhook*, when given, must be a function that takes two arguments,
|
|
*filename* and *mode*, and returns an accordingly opened file-like object. You
|
|
cannot use *inplace* and *openhook* together.
|
|
|
|
A :class:`FileInput` instance can be used as a context manager in the
|
|
:keyword:`with` statement. In this example, *input* is closed after the
|
|
:keyword:`!with` statement is exited, even if an exception occurs::
|
|
|
|
with FileInput(files=('spam.txt', 'eggs.txt')) as input:
|
|
process(input)
|
|
|
|
.. versionchanged:: 3.2
|
|
Can be used as a context manager.
|
|
|
|
.. deprecated:: 3.4
|
|
The ``'rU'`` and ``'U'`` modes.
|
|
|
|
.. deprecated-removed:: 3.6 3.8
|
|
The *bufsize* parameter.
|
|
|
|
|
|
**Optional in-place filtering:** if the keyword argument ``inplace=True`` is
|
|
passed to :func:`fileinput.input` or to the :class:`FileInput` constructor, the
|
|
file is moved to a backup file and standard output is directed to the input file
|
|
(if a file of the same name as the backup file already exists, it will be
|
|
replaced silently). This makes it possible to write a filter that rewrites its
|
|
input file in place. If the *backup* parameter is given (typically as
|
|
``backup='.<some extension>'``), it specifies the extension for the backup file,
|
|
and the backup file remains around; by default, the extension is ``'.bak'`` and
|
|
it is deleted when the output file is closed. In-place filtering is disabled
|
|
when standard input is read.
|
|
|
|
|
|
The two following opening hooks are provided by this module:
|
|
|
|
.. function:: hook_compressed(filename, mode)
|
|
|
|
Transparently opens files compressed with gzip and bzip2 (recognized by the
|
|
extensions ``'.gz'`` and ``'.bz2'``) using the :mod:`gzip` and :mod:`bz2`
|
|
modules. If the filename extension is not ``'.gz'`` or ``'.bz2'``, the file is
|
|
opened normally (ie, using :func:`open` without any decompression).
|
|
|
|
Usage example: ``fi = fileinput.FileInput(openhook=fileinput.hook_compressed)``
|
|
|
|
|
|
.. function:: hook_encoded(encoding, errors=None)
|
|
|
|
Returns a hook which opens each file with :func:`open`, using the given
|
|
*encoding* and *errors* to read the file.
|
|
|
|
Usage example: ``fi =
|
|
fileinput.FileInput(openhook=fileinput.hook_encoded("utf-8",
|
|
"surrogateescape"))``
|
|
|
|
.. versionchanged:: 3.6
|
|
Added the optional *errors* parameter.
|