Map/reduce的应用

将字符串转为整型：

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))

累乘函数：

from functools import reduce
def prod(s):
	def fn(x,y):
		return x*y
	return reduce(fn,s)
#case
print('3*5*7*9=',prod([3,5,7,9]))