fileinput — Iterate over lines from multiple input streams
Source code: 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
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 and the optional arguments mode and openhook are ignored. 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
FileInput. If an I/O error occurs during opening or reading a file,
OSError is raised.
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
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
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:
fileinput.input(files=None, inplace=False, backup='', *, mode='r', openhook=None)
Create an instance of the
FileInputclass. 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
with fileinput.input(files=('spam.txt', 'eggs.txt')) as f: for line in f: process(line)
Changed in version 3.2: Can be used as a context manager.
Changed in version 3.8: The keyword parameters mode and openhook are now keyword-only.
Return the name of the file currently being read. Before the first line has been read, returns
Return the integer “file descriptor” for the current file. When no file is opened (before the first line and between files), returns
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.
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.
Trueif the line just read is the first line of its file, otherwise return
Trueif the last line was read from
sys.stdin, otherwise return
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.
Close the sequence.
The class which implements the sequence behavior provided by the module is available for subclassing as well:
class fileinput.FileInput(files=None, inplace=False, backup='', *, mode='r', openhook=None)
FileInputis the implementation; its methods
close()correspond to the functions of the same name in the module. In addition it has a
readline()method which returns the next input line, and a
__getitem__()method which implements the sequence behavior. The sequence must be accessed in strictly sequential order; random access and
readline()cannot be mixed.
With mode you can specify which file mode will be passed to
open(). It must be one of
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.
with FileInput(files=('spam.txt', 'eggs.txt')) as input: process(input)
Changed in version 3.2: Can be used as a context manager.
Deprecated since version 3.4: The
Deprecated since version 3.8: Support for
__getitem__()method is deprecated.
Changed in version 3.8: The keyword parameter mode and openhook are now keyword-only.
Optional in-place filtering: if the keyword argument
inplace=True is passed to
fileinput.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 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:
Transparently opens files compressed with gzip and bzip2 (recognized by the extensions
'.bz2') using the
bz2modules. If the filename extension is not
'.bz2', the file is opened normally (ie, using
open()without any decompression).
fi = fileinput.FileInput(openhook=fileinput.hook_compressed)
Returns a hook which opens each file with
open(), using the given encoding and errors to read the file.
fi = fileinput.FileInput(openhook=fileinput.hook_encoded("utf-8", "surrogateescape"))
Changed in version 3.6: Added the optional errors parameter.
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