summaryrefslogtreecommitdiffstats
path: root/Doc/library/fileinput.rst
diff options
context:
space:
mode:
authorGeorg Brandl <georg@python.org>2007-08-15 14:28:22 (GMT)
committerGeorg Brandl <georg@python.org>2007-08-15 14:28:22 (GMT)
commit116aa62bf54a39697e25f21d6cf6799f7faa1349 (patch)
tree8db5729518ed4ca88e26f1e26cc8695151ca3eb3 /Doc/library/fileinput.rst
parent739c01d47b9118d04e5722333f0e6b4d0c8bdd9e (diff)
downloadcpython-116aa62bf54a39697e25f21d6cf6799f7faa1349.zip
cpython-116aa62bf54a39697e25f21d6cf6799f7faa1349.tar.gz
cpython-116aa62bf54a39697e25f21d6cf6799f7faa1349.tar.bz2
Move the 3k reST doc tree in place.
Diffstat (limited to 'Doc/library/fileinput.rst')
-rw-r--r--Doc/library/fileinput.rst183
1 files changed, 183 insertions, 0 deletions
diff --git a/Doc/library/fileinput.rst b/Doc/library/fileinput.rst
new file mode 100644
index 0000000..d0a3ed9
--- /dev/null
+++ b/Doc/library/fileinput.rst
@@ -0,0 +1,183 @@
+: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.
+
+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.
+
+**Caveat:** 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
+