python中的Counter

最新推荐文章于 2025-03-01 17:24:26 发布

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本文介绍如何使用Python的collections模块中的Counter函数来统计字符串中各字符的出现次数，并通过示例展示了如何将计数结果转换为字典以及按字符出现频率进行排序的方法。

统计字符串中的字符数量用Counter函数

    def __init__(*args, **kwds):
        '''Create a new, empty Counter object.  And if given, count elements
        from an input iterable.  Or, initialize the count from another mapping
        of elements to their counts.

        >>> c = Counter()                           # a new, empty counter
        >>> c = Counter('gallahad')                 # a new counter from an iterable
        >>> c = Counter({'a': 4, 'b': 2})           # a new counter from a mapping
        >>> c = Counter(a=4, b=2)                   # a new counter from keyword args

        '''
        if not args:
            raise TypeError("descriptor '__init__' of 'Counter' object "
                            "needs an argument")
        self, *args = args
        if len(args) > 1:
            raise TypeError('expected at most 1 arguments, got %d' % len(args))
        super(Counter, self).__init__()
        self.update(*args, **kwds)

示例：

#统计字符串中个字母的次数并排序

from collections import Counter

st = "1a,2b,3c,aa,bb,cc,22,33,11,ab,ac,bc"
counter = Counter(st)  # 字符计数
counter_to_dict = dict(counter)   # 返回值字典化
dict_change = {}   # 空字典存储排序后的字典
for x in sorted(counter_to_dict.items(), key=None, reverse=True):  # 降序
    dict_change[x[0]] = x[1]

print(type(counter), counter)
print(type(counter_to_dict), counter_to_dict)
print(dict_change)

结果：

D:\mypy\venv\Scripts\python.exe D:/mypy/conuter.py
<class 'collections.Counter'> Counter({',': 11, 'a': 5, 'b': 5, 'c': 5, '1': 3, '2': 3, '3': 3})
<class 'dict'> {'1': 3, 'a': 5, ',': 11, '2': 3, 'b': 5, '3': 3, 'c': 5}
{'c': 5, 'b': 5, 'a': 5, '3': 3, '2': 3, '1': 3, ',': 11}

Process finished with exit code 0