nl.py

nl.py

import sys

def nl(lines):
    i = 1
    for line in lines:
        if line == '\n':
            print("{0}".format(line), end="")
        else:
            print("    {0} {1}".format(i, line), end="")
            i += 1
    return

argc = len(sys.argv)
if argc == 1:
    lines = sys.stdin.readlines()
    nl(lines)
elif argc == 2:
    try:
        f = open(sys.argv[1], 'rU')
        lines = f.readlines()
        nl(lines)
    except IOError:
        print("Error: open file", sys.stderr)
        sys.exit(1)
    f.close()
else:
    sys.exit("usage: nl [file]")