A new standard module, as discussed on comp.lang.python, to simplify
the writing of filters.
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 or when a filename is
'-'.
There is also an option to use this to direct the output back to the
input files.
This commit is contained in:
Guido van Rossum
parent
2aa78efab1
commit
7d5b99d8bf
|
|
@ -0,0 +1,254 @@
|
|||
"""Helper class to quickly write a loop over all standard input files.
|
||||
|
||||
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 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. If an I/O error occurs during
|
||||
opening or reading a file, the IOError 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)).
|
||||
|
||||
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(), fileline(), isfirstline(), isstdin(), nextfile() and close()
|
||||
correspond to the functions 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; 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.
|
||||
|
||||
XXX Possible additions:
|
||||
|
||||
- optional getopt argument processing
|
||||
- specify open mode ('r' or 'rb')
|
||||
- specify buffer size
|
||||
- fileno()
|
||||
- isatty()
|
||||
- read(), read(size), even readlines()
|
||||
|
||||
"""
|
||||
|
||||
import sys, os
|
||||
|
||||
_state = None
|
||||
|
||||
def input(files=(), inplace=0, backup=""):
|
||||
global _state
|
||||
if _state and _state._file:
|
||||
raise RuntimeError, "input() already active"
|
||||
_state = FileInput(files, inplace, backup)
|
||||
return _state
|
||||
|
||||
def close():
|
||||
global _state
|
||||
state = _state
|
||||
_state = None
|
||||
if state:
|
||||
state.close()
|
||||
|
||||
def nextfile():
|
||||
if not _state:
|
||||
raise RuntimeError, "no active input()"
|
||||
return _state.nextfile()
|
||||
|
||||
def filename():
|
||||
if not _state:
|
||||
raise RuntimeError, "no active input()"
|
||||
return _state.filename()
|
||||
|
||||
def lineno():
|
||||
if not _state:
|
||||
raise RuntimeError, "no active input()"
|
||||
return _state.lineno()
|
||||
|
||||
def filelineno():
|
||||
if not _state:
|
||||
raise RuntimeError, "no active input()"
|
||||
return _state.filelineno()
|
||||
|
||||
def isfirstline():
|
||||
if not _state:
|
||||
raise RuntimeError, "no active input()"
|
||||
return _state.isfirstline()
|
||||
|
||||
def isstdin():
|
||||
if not _state:
|
||||
raise RuntimeError, "no active input()"
|
||||
return _state.isstdin()
|
||||
|
||||
class FileInput:
|
||||
|
||||
def __init__(self, files=(), inplace=0, backup=""):
|
||||
if type(files) == type(''):
|
||||
files = (files,)
|
||||
else:
|
||||
files = tuple(files)
|
||||
if not files:
|
||||
files = tuple(sys.argv[1:])
|
||||
if not files:
|
||||
files = ('-',)
|
||||
self._files = files
|
||||
self._inplace = inplace
|
||||
self._backup = backup
|
||||
self._savestdout = None
|
||||
self._output = None
|
||||
self._filename = None
|
||||
self._lineno = 0
|
||||
self._filelineno = 0
|
||||
self._file = None
|
||||
self._isstdin = 0
|
||||
|
||||
def __del__(self):
|
||||
self.close()
|
||||
|
||||
def close(self):
|
||||
self.nextfile()
|
||||
self._files = ()
|
||||
|
||||
def __getitem__(self, i):
|
||||
if i != self._lineno:
|
||||
raise RuntimeError, "accessing lines out of order"
|
||||
line = self.readline()
|
||||
if not line:
|
||||
raise IndexError, "end of input reached"
|
||||
return line
|
||||
|
||||
def nextfile(self):
|
||||
savestdout = self._savestdout
|
||||
self._savestdout = 0
|
||||
if savestdout:
|
||||
sys.stdout = savestdout
|
||||
|
||||
output = self._output
|
||||
self._output = 0
|
||||
if output:
|
||||
output.close()
|
||||
|
||||
file = self._file
|
||||
self._file = 0
|
||||
if file and not self._isstdin:
|
||||
file.close()
|
||||
|
||||
backupfilename = self._backupfilename
|
||||
self._backupfilename = 0
|
||||
if backupfilename and not self._backup:
|
||||
try: os.unlink(backupfilename)
|
||||
except: pass
|
||||
|
||||
self._isstdin = 0
|
||||
|
||||
def readline(self):
|
||||
if not self._file:
|
||||
if not self._files:
|
||||
return ""
|
||||
self._filename = self._files[0]
|
||||
self._files = self._files[1:]
|
||||
self._filelineno = 0
|
||||
self._file = None
|
||||
self._isstdin = 0
|
||||
self._backupfilename = 0
|
||||
if self._filename == '-':
|
||||
self._filename = '<stdin>'
|
||||
self._file = sys.stdin
|
||||
self._isstdin = 1
|
||||
else:
|
||||
if self._inplace:
|
||||
self._backupfilename = (
|
||||
self._filename + (self._backup or ".bak"))
|
||||
try: os.unlink(self._backupfilename)
|
||||
except os.error: pass
|
||||
# The next three lines may raise IOError
|
||||
os.rename(self._filename, self._backupfilename)
|
||||
self._file = open(self._backupfilename, "r")
|
||||
self._output = open(self._filename, "w")
|
||||
self._savestdout = sys.stdout
|
||||
sys.stdout = self._output
|
||||
else:
|
||||
# This may raise IOError
|
||||
self._file = open(self._filename, "r")
|
||||
line = self._file.readline()
|
||||
if line:
|
||||
self._lineno = self._lineno + 1
|
||||
self._filelineno = self._filelineno + 1
|
||||
return line
|
||||
self.nextfile()
|
||||
# Recursive call
|
||||
return self.readline()
|
||||
|
||||
def filename(self):
|
||||
return self._filename
|
||||
|
||||
def lineno(self):
|
||||
return self._lineno
|
||||
|
||||
def filelineno(self):
|
||||
return self._filelineno
|
||||
|
||||
def isfirstline(self):
|
||||
return self._filelineno == 1
|
||||
|
||||
def isstdin(self):
|
||||
return self._isstdin
|
||||
|
||||
def _test():
|
||||
import getopt
|
||||
inplace = 0
|
||||
backup = 0
|
||||
opts, args = getopt.getopt(sys.argv[1:], "ib:")
|
||||
for o, a in opts:
|
||||
if o == '-i': inplace = 1
|
||||
if o == '-b': backup = a
|
||||
for line in input(args, inplace=inplace, backup=backup):
|
||||
if line[-1:] == '\n': line = line[:-1]
|
||||
if line[-1:] == '\r': line = line[:-1]
|
||||
print "%d: %s[%d]%s %s" % (lineno(), filename(), filelineno(),
|
||||
isfirstline() and "*" or "", line)
|
||||
print "%d: %s[%d]" % (lineno(), filename(), filelineno())
|
||||
|
||||
if __name__ == '__main__':
|
||||
_test()
|
||||
Loading…
Reference in New Issue