求阶乘

 求阶乘：

方式一：递归求阶乘

def jiecheng(x):
    if (x-1 ==0):
        return x
    x = x*jiecheng( x-1 )
    return x
print(jiecheng(9))

方式而：匿名函数+reduce+range

from functools import reduce
print(reduce( lambda x,y:x*y,range(1,5)))            # 求1-4的阶乘，根据所求相应改变