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1、统计文件中第一个单词出现的次数 方法一：先把所有不重复的首个单词保存为列表，然后用字典的fromkeys方法把字典初始化为键为首单词值为0的字典，最后再循环一次统计单词出现的次数，该方法的算法复杂度较高，如文件有n行，则为O(n*n) def count_word(): count = {} keys = [] with open('test.txt') as f: lines = f.readlines() for line in lines: first_word = line.split(' ')[0] if first_word not in keys: keys.append(first_word) count = count.fromkeys(keys,0) #fromkeys方法不会直接修改原字典，它会返回一个新字典，所以如果要使用心字典必须先赋值 print(count) for line in lines: first_word = line.split(' ')[0] count[first_word] +=1 print(count)方法二：在找到每行的第一个单词时，先用字典的has_key方法确认字典中是否有这个键，如无，则新增键为该单词，值为1的项，如字典已有该项，则该项的值+1，该算法复杂度为O(n) def count_word(): count = {} with open('test.txt') as f: lines = f.readlines() for line in lines: first_word = line.split(' ')[0] if count.has_key(first_word): count[first_word] +=1 else: count[first_word] = 1 print(count)2、统计一篇文章中某个单词的出现次数 分别用两个for循环即可，for line in lines: for word in line.split(' '): def count_word(): mark_word = 'error' count = 0 with open('test.txt') as f: lines = f.readlines() for line in lines: for word in line.split(' '): if word == mark_word: count +=1 print(count)
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