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, '': 1, '': 2, '': 3, '': 4, '': 5, '': 6, '': 7, '': 8, '': 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]) #
     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'))