# -*- coding: utf-8 -*-

# 创建字母字典
def createCharacterCounts(CharacterCounts):
    for i in range(97, 123):
        CharacterCounts[chr(i)] = 0


def processLine(line, CharacterCounts):
    for character in line:
        if ord(character) in range(97, 123):
            CharacterCounts[character] += 1





def main():
    # 用户输入一个文件名
    # filename = input("enter a filename:").strip()
    filename = "A_Tale_of_Two_Cities.txt"
    infile = open(filename, "r")

    # 建立用于计算词频的空字典
    CharacterCounts = {}
    # 初始化字典键值
    createCharacterCounts(CharacterCounts)
    for line in infile:
        processLine(line.lower(), CharacterCounts)

    # 从字典中获取数据对
    pairs = list(CharacterCounts.items())

    # 列表中的数据对交换位置,数据对排序
    items = [[x, y] for (y, x) in pairs]
    items.sort(reverse=True)

    # 输出count个数词频结果
    for i in range(len(items)):
        print(items[i][1] + "\t" + str(items[i][0]))

    infile.close()


# 调用main()函数
if __name__ == '__main__':
    main()