Python 实现 英语 单词统计 和替换

def count_en(a, word):
        index = 0
        times = 0
        len_str = len(a)
        len_word = len(word)
        while True:
                index = a.find(word, index)
                if index == -1:
                        break
                #第一个词
                if index != 0:
                        front = a[index-1]
                else:
                        front = ""
                #if f is not word it will be my word
                back_index = (index + len_word)
                #最后一个词
                if back_index < len_str:
                        back = a[back_index]
                else:
                        back = ""
                index += len_word
                if front.isalpha() or back.isalpha():
                        continue
                times+=1
        #print times
        return times

 

 

def replace_en(a, word, newword):
        index = 0
        len_word = len(word)
        len_new_word= len(newword)
        new_str = a
        i = 0
        while True:
                #i+=1
                #print i
                index = new_str.find(word, index)
                if index == -1:
                        break
                #第一个词
                front_index = index
                if index != 0:
                        front = new_str[index-1]
                else:
                        front = ""
                #if f is not word it will be my word
                back_index = (index + len_word)
                #最后一个词
                len_t = len(new_str)
                if back_index < len_t:
                        back = new_str[back_index]
                else:
                        back = ""
                #new_word = a[:index-1] 
                if front.isalpha() or back.isalpha():
                        index += len_word
                        continue
                else:
                        index += 13
                ff = new_str[:front_index]
                bb = new_str[back_index:]
                new_str = ff + newword + bb
        return new_str