Python高级函数--map/reduce

名字开头大写 后面小写；练习：

def normalize(name):
    return name[0].upper() + name[1:].lower()
L1 = ['adam', 'LISA', 'barT']
L2 = list(map(normalize, L1))
print(L2)

reduce求积：

from functools import reduce

def prod(L):
    def fn(x, y):
        return x * y
    return reduce(fn, L)
print('3 * 5 * 7 * 9 =', prod([3, 5, 7, 9]))

reduce把结果继续和序列的下一个元素做累积计算

字符串转浮点数练习：

from functools import reduce

def str2int(s):
    def char2num(c):
        return { '0': 0, '1': 1, '2': 2, '3': 3, '4': 4, '5': 5, '6': 6, '7': 7, '8': 8, '9': 9}[c]
    return reduce(lambda x, y: x *10 + y, map(char2num, s))

def str2float(s):
    s_list = s.split('.')
    float_i = str2int(s_list[0]) #123
    float_f = str2int(s_list[1]) / (10**len(s_list[1])) #456/1000
    return float_i + float_f
print('str2float('123.456') =', str2float('123.456'))