# !/usr/bin/python3
# -*-coding:UTF-8-*-
# FileName: func_str2float.py

from functools import reduce

DIGITS = {'0': 0, '1': 1, '2': 2, '3': 3, '4': 4, '5': 5, '6': 6, '7': 7, '8': 8, '9': 9}
str2int = lambda s: reduce(lambda x, y: x * 10 + y, map(lambda c: DIGITS[c], s))

def str2float(s):
    ''' 利用map和reduce编写一个str2float函数，
        把字符串'123.456'转换成浮点数123.456
    '''
    tup = s.partition(".")      #返回3元的元组: (左边的子串，分隔符，右边的子串)
    num = float(f'{str2int(tup[0])}.{str2int(tup[2])}')

    return num

if __name__ == '__main__':

    print('str2float(\'123.456\') =', str2float('123.456'))
    if abs(str2float('123.456') - 123.456) < 0.00001:
        print('测试成功!')
    else:
        print('测试失败!')