: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>

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:`IOError` is raised.

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[, inplace[, backup[, mode[, openhook]]]]])

   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.

   .. versionchanged:: 2.5

      Added the *mode* and *openhook* parameters.

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``.

   .. versionadded:: 2.5

.. 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[, inplace[, backup[, mode[, openhook]]]]])

   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:`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:`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.

   .. versionchanged:: 2.5

      Added the *mode* and *openhook* parameters.

**Optional in-place filtering:** if the keyword argument ``inplace=1`` 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.

.. warning::

   The current implementation does not work for MS-DOS 8+3 filesystems.

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)``

   .. versionadded:: 2.5

.. function:: hook_encoded(encoding)

   Returns a hook which opens each file with :func:`codecs.open`, using the given

   *encoding* to read the file.

   Usage example: ``fi =

   fileinput.FileInput(openhook=fileinput.hook_encoded("iso-8859-1"))``

   .. note::

      With this hook, :class:`FileInput` might return Unicode strings depending on the

      specified *encoding*.

   .. versionadded:: 2.5