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 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 input() or FileInput(). If an I/O error occurs during opening or reading a file, 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.
It is possible that the last line of a file does not end in a newline character; lines are returned including the trailing newline when it is present.
You can control how files are opened by providing an opening hook via the openhook parameter to input() or 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:
[files[, inplace[, backup[, mode[, openhook]]]]]) |
Changed in version 2.5: Added the mode and openhook parameters.
The following functions use the global state created by input(); if there is no active state, RuntimeError is raised.
) |
None
.
) |
-1
.
New in version 2.5.
) |
0
. After
the last line of the last file has been read, returns the line
number of that line.
) |
0
. After the last line of the last
file has been read, returns the line number of that line within the
file.
) |
) |
sys.stdin
,
otherwise returns false.
) |
) |
The class which implements the sequence behavior provided by the module is available for subclassing as well:
[files[, inplace[, backup[, mode[, openhook]]]]]) |
With mode you can specify which file mode will be passed to
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.
Changed in version 2.5: Added the mode and openhook parameters.
Optional in-place filtering: if the keyword argument
inplace=1
is passed to input() or to the
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 keyword argument backup='.<some
extension>'
is also given, 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:
filename, mode) |
'.gz'
and '.bz2'
) using the gzip
and bz2 modules. If the filename extension is not '.gz'
or '.bz2'
, the file is opened normally (ie,
using open() without any decompression).
Usage example: "fi = fileinput.FileInput(openhook=fileinput.hook_compressed)"
New in version 2.5.
encoding) |
Usage example: "fi = fileinput.FileInput(openhook=fileinput.hook_encoded("iso-8859-1"))"
Note: With this hook, FileInput might return Unicode strings depending on the specified encoding. New in version 2.5.