# pydoc > fileinput

Help on module fileinput:

## NAME
    fileinput - Helper class to quickly write a loop over all standard input files.

## MODULE REFERENCE
    <https://docs.python.org/3.12/library/fileinput.html>

    The following documentation is automatically generated from the Python
    source files.  It may be incomplete, incorrect or include features that
    are considered implementation detail and may vary between Python
    implementations.  When in doubt, consult the module reference at the
    location listed above.

## DESCRIPTION
    Typical use is:

        import fileinput
        for line in fileinput.input(encoding="utf-8"):
            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 argument to input().  A single file name is also allowed.

    Functions filename(), lineno() return the filename and cumulative line
    number of the line that has just been read; filelineno() returns its
    line number in the current file; isfirstline() returns true iff the
    line just read is the first line of its file; isstdin() returns true
    iff the line was read from sys.stdin.  Function nextfile() closes 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.  Function close()
    closes the sequence.

    Before any lines have been read, filename() returns None and both line
    numbers are zero; nextfile() has no effect.  After all lines have been
    read, filename() and the line number functions return the values
    pertaining to the last line read; nextfile() has no effect.

    All files are opened in text mode by default, you can override this by
    setting the mode parameter to input() or FileInput.__init__().
    If an I/O error occurs during opening or reading a file, the OSError
    exception 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)](https://www.chedong.com/phpMan.php/man/sys.stdin.seek/0/markdown)).

    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 doesn't end in a newline
    character; otherwise lines are returned including the trailing
    newline.

    Class FileInput is the implementation; its methods filename(),
### lineno
    correspond to the functions in the module.  In addition it has a
### readline
    __getitem__() method which implements the sequence behavior.  The
    sequence must be accessed in strictly sequential order; sequence
    access and readline() cannot be mixed.

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

## CLASSES
    builtins.object
        FileInput

### class FileInput
     |  FileInput(files=None, inplace=False, backup='', *, mode='r', openhook=None, encoding=None, errors=None)
     |
     |  FileInput([files[, inplace[, backup]]], *, mode=None, openhook=None)
     |
     |  Class FileInput is the implementation of the module; its methods
     |  filename(), lineno(), fileline(), isfirstline(), isstdin(), fileno(),
     |  nextfile() and 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.
     |
     |  Methods defined here:
     |
     |  __del__(self)
     |
     |  __enter__(self)
     |
     |  __exit__(self, type, value, traceback)
     |
     |  __init__(self, files=None, inplace=False, backup='', *, mode='r', openhook=None, encoding=None, errors=None)
     |      Initialize self.  See help(type(self)) for accurate signature.
     |
     |  __iter__(self)
     |
     |  __next__(self)
     |
     |  close(self)
     |
     |  filelineno(self)
     |
     |  filename(self)
     |
     |  fileno(self)
     |
     |  isfirstline(self)
     |
     |  isstdin(self)
     |
     |  lineno(self)
     |
     |  nextfile(self)
     |
     |  readline(self)
     |
     |  ----------------------------------------------------------------------
     |  Class methods defined here:
     |
     |  __class_getitem__ = GenericAlias(...)
     |      Represent a PEP 585 generic type
     |
     |      E.g. for t = list[int], t.__origin__ is list and t.__args__ is (int,).
     |
     |  ----------------------------------------------------------------------
     |  Data descriptors defined here:
     |
     |  __dict__
     |      dictionary for instance variables
     |
     |  __weakref__
     |      list of weak references to the object

## FUNCTIONS
### close
        Close the sequence.

### 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.

### filename
        Return the name of the file currently being read.
        Before the first line has been read, returns None.

### fileno
        Return the file number of the current file. When no file is currently
        opened, returns -1.

### hook_compressed

### hook_encoded

### input
        Return an instance of the FileInput class, which can be iterated.

        The parameters are passed to the constructor of the FileInput class.
        The returned instance, in addition to being an iterator,
        keeps global state for the functions of this module,.

### isfirstline
        Returns true the line just read is the first line of its file,
        otherwise returns false.

### isstdin
        Returns true if the last line was read from sys.stdin,
        otherwise returns false.

### 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.

### 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.

## DATA
    __all__ = ['input', 'close', 'nextfile', 'filename', 'lineno', 'fileli...

## FILE
    /usr/lib/python3.12/fileinput.py