python统计单词出现次数

# -*- coding:utf-8 -*-
import io
import re

class Counter:
    def __init__(self, path):
        """
        :param path: 文件路径
        """
        self.mapping = dict()
        with io.open(path, encoding="utf-8") as f:
            data = f.read()
            words = [s.lower() for s in re.findall("\w+", data)]
            for word in words:
                self.mapping[word] = self.mapping.get(word, 0) + 1

    def most_common(self, n):
        assert n > 0, "n should be large than 0"
        return sorted(self.mapping.items(), key=lambda item: item[1], reverse=True)[:n]

if __name__ == '__main__':
    most_common_5 = Counter("importthis.txt").most_common(5)
    for item in most_common_5:
        print(item)

('is', 10)
('better', 8)
('than', 8)
('the', 6)
('to', 5)