用python2.7.9 写个小程序搜索某个目录下行有某关键字

# -*- coding: utf-8 -*-
import sys
reload(sys)
sys.setdefaultencoding("utf-8")
import os
def print_pos(key_dict):
    keys = key_dict.keys()
    keys = sorted(keys)  # 由于字典是无序的，我们这里对行数进行排序
    for each_key in keys:
        print('关键字出现在第 %s 行，第 %s 个位置。' % (each_key, str(key_dict[each_key])))
def pos_in_line(line, key):
    pos = []
    begin = line.find(key)
    while begin != -1:
        pos.append(begin + 1)  # 用户的角度是从1开始数
        begin = line.find(key, begin + 1)  # 从下一个位置继续查找
    return pos
def search_in_file(file_name, key):
    f = open(file_name,'r')
    count = 0  # 记录行数
    key_dict = dict()  # 字典，用户存放key所在具体行数对应具体位置
    for each_line in f:
        count += 1
        if key in each_line:
            pos = pos_in_line(each_line, key)  # key在每行对应的位置
            key_dict[count] = pos
    f.close()
    return key_dict
def search_files(key, detail):
    all_files = os.walk(os.getcwd())
    txt_files = []
    for i in all_files:
        for each_file in i[2]:
            if os.path.splitext(each_file)[1] == '.txt':  # 根据后缀判断是否文本文件
                each_file = os.path.join(i[0], each_file)
                txt_files.append(each_file)
    for each_txt_file in txt_files:
        key_dict = search_in_file(each_txt_file, key)
        if key_dict:
            print '================================================================'
            print '在文件【%s】中找到关键字【%s】' % (each_txt_file, key)
            if detail in ['YES', 'Yes', 'yes']:
                print_pos(key_dict)
key = raw_input('请将该脚本放于待查找的文件夹内，请输入关键字：')
detail = raw_input('请问是否需要打印关键字【%s】在文件中的具体位置（YES/NO）：' % key)
search_files(key, detail)