fileinput --- 逐列疊代多個輸入串流¶原始碼：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 open().
The 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
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,
OSError 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 fileinput.input() or FileInput(). The
hook must be a function that takes two arguments, filename and mode, and
returns an accordingly opened file-like object. If encoding and/or errors
are specified, they will be passed to the hook as additional keyword arguments.
This module provides a hook_compressed() to support compressed files.
The following function is the primary interface of this module:
Create an instance of the 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 FileInput class.
The FileInput instance can be used as a context manager in the
with statement. In this example, input is closed after the
with statement is exited, even if an exception occurs:
with fileinput.input(files=('spam.txt', 'eggs.txt'), encoding="utf-8") as f:
for line in f:
process(line)
在 3.2 版的變更: Can be used as a context manager.
在 3.8 版的變更: The keyword parameters mode and openhook are now keyword-only.
在 3.10 版的變更: The keyword-only parameter encoding and errors are added.
The following functions use the global state created by fileinput.input();
if there is no active state, RuntimeError is raised.
Return the name of the file currently being read. Before the first line has
been read, returns None.
Return the integer "file descriptor" for the current file. When no file is
opened (before the first line and between files), returns -1.
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.
Return True if the line just read is the first line of its file, otherwise
return False.
Return True if the last line was read from sys.stdin, otherwise return
False.
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 is the implementation; its methods filename(),
fileno(), lineno(), filelineno(), isfirstline(),
isstdin(), nextfile() and close() correspond to the
functions of the same name in the module. In addition it is iterable
and has a readline() method which returns the next
input line. 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 'r' 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.
You can specify encoding and errors that is passed to open() or openhook.
A FileInput instance can be used as a context manager in the
with statement. In this example, input is closed after the
with statement is exited, even if an exception occurs:
with FileInput(files=('spam.txt', 'eggs.txt')) as input:
process(input)
在 3.2 版的變更: Can be used as a context manager.
在 3.8 版的變更: The keyword parameter mode and openhook are now keyword-only.
在 3.10 版的變更: The keyword-only parameter encoding and errors are added.
在 3.11 版的變更: The 'rU' and 'U' modes and the __getitem__() method have
been removed.
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 '.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).
The encoding and errors values are passed to io.TextIOWrapper
for compressed files and open for normal files.
Usage example: fi = fileinput.FileInput(openhook=fileinput.hook_compressed, encoding="utf-8")
在 3.10 版的變更: The keyword-only parameter encoding and errors are added.
Returns a hook which opens each file with open(), using the given
encoding and errors to read the file.
Usage example: fi =
fileinput.FileInput(openhook=fileinput.hook_encoded("utf-8",
"surrogateescape"))
在 3.6 版的變更: 新增可選參數 errors。
在 3.10 版之後被棄用: This function is deprecated since fileinput.input() and FileInput
now have encoding and errors parameters.