Python Standard Library

The posixfile Module

(Obsolete, Unix only) The posixfile module provides a file-like object with support for file locking, as Example 14-27 shows. New programs should use the fcntl module instead.

Example 14-27. Using the posixfile Module

File: posixfile-example-1.py

import posixfile
import string

filename = "counter.txt"

try:
    # open for update
    file = posixfile.open(filename, "r+")
    counter = int(file.read(6)) + 1
except IOError:
    # create it
    file = posixfile.open(filename, "w")
    counter = 0

file.lock("w|", 6)

file.seek(0) # rewind
file.write("%06d" % counter)

file.close() # releases lock