通过python实现linux中的wc命令，学习python参数处理模块optparse

#!/usr/bin/env python
# coding=utf-8

import sys, os
from optparse import OptionParser

def opt():
    parser = OptionParser()
    parser.add_option("-c", "--char",
                      dest="chars",
                      action="store_true",
                      default=False,
                      help="only count chars")
    parser.add_option("-w", "--ward",
                      dest="words",
                      action="store_true",
                      default=False,
                      help="only count words")
    parser.add_option("-l", "--line",
                      dest="lines",
                      action="store_true",
                      default=False,
                      help="only count lines")
    parser.add_option("-n", "--no-total",
                      dest="nototal",
                      action="store_true",
                      default=False,
                      help="show total or not")
    options, args = parser.parse_args()
    return options, args

def get_count(data):
    chars =  len(data)
    words = len(data.split())
    lines = data.count('\n')
    return lines, words, chars

def print_wc(options, lines, words, chars, fn):
    if options.lines:
        print lines,
    if options.words:
        print words,
    if options.chars:
        print chars,
    print(fn)

def main():
    options, args = opt()
    if not (options.words or options.chars or options.lines):
        options.words, options.chars, options.lines = True, True, True

    if args:
        total_lines, total_words, total_chars = 0, 0, 0
        for fn in args:
            if os.path.isfile(fn):
                with open(fn) as fd:
                    data = fd.read()
                lines, words, chars = get_count(data)
                print_wc(options, lines, words, chars, fn)
                total_lines += lines
                total_words += words
                total_chars += chars
            elif os.path.isdir(fn):
                print("%s: is a directory" % fn, file=sys.stderr)
            else:
                sys.stderr.write("%s: No such file or direcotry\n" % fn)
        if len(args) > 1 and not options.nototal:
            print_wc(options, total_lines, total_words, total_chars, 'total')
    else:
        data = sys.stdin.read()
        fn = ''
        lines, words, chars = get_count(data)
        print_wc(options, lines, words, chars, fn)

if __name__ == '__main__':
    main()