reads directly from the password file

#!/usr/bin/python

# List the account and human names from the passwd file in sorted order.  
# If there is no human name, or it equals the userid, then the name is
# printed as [ none ].   The program reads from the file given the command
# line, if any,  else it reads from /etc/passwd.  If the file open fails, the
# program will die on an exception.

# The from form of of import adds name to the symbol table of the
# importing program, so that the names may be refered to without
# the qualified module name.
from sys import argv
from string import *

# Dictionary of entries.
iddict = { }

# Get the file name.  Note that argv[0] contains the name of the script,
# so we're getting argv[1], if there is one.
infile = '/etc/passwd'
if len(argv) > 1:
    infile = argv[1]

# Attempt to open the file.  Will just let the program die on the exception
# if the open fails.
fin = open(infile, 'r')

# Loop through each input line.
for line in fin.readlines():
    # Lines starting with # are comments.  Clean leading spaces, and