map(函数名，Iterable),map接受两个参数，一个是函数，一个是可迭代对象

>>> def f(x):
	return x**3

>>> res = map(f,[1,2,3,4,5])
>>> 
>>> res
<map object at 0x0000000002F1A080>
>>> list(res)
[1, 8, 27, 64, 125]

将int数组转换成str数组

>>> list(map(str,[1,2,3,4,5]))
['1', '2', '3', '4', '5']

reduce（f,[x1,x2,x3,x4]） = f(f(f(x1,x2),x3),x4)

利用reduce和map 写str2int（）函数

>>> 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,}

>>> def str2int(s):
	def fn(x,y):
		return x*10+y
	def char2num(s):
		return Digits[s]
	return reduce(fn,map(char2num,s))

>>> str2int('12344')
12344

# -*- coding: utf-8 -*-
from functools import reduce

def str2float(s):
     Digits = {'0':0,'1':1,'2':2,'3':3,'4':4,'5':5,'6':6,'7':7,'8':8,'9':9,}
     def char2num(s):
         return Digits[s]
     def f(x,y):
         return x*10+y
     def p(x,y):
         return x/10+y
     if '.' in s:
         list_num = s.split('.')
         m = reduce(f,map(char2num,list_num[0]))
         newlist = list(map(char2num,list_num[1]))
         newlist.reverse()
         n = reduce(p,newlist)
         return m+n/10
     else:
         return reduce(f,map(char2num,s))