python计算阶乘函数

#从functools中调用reduce()函数
from functools import reduce
#使用lambda，匿名函数，迭代
num = reduce(lambda x,y:x*y,range(1,n))  # 计算n的阶乘
print(num)

import math
value = math.factorial(n)  # 计算n的阶乘
print(value)

def main(num):
    a=1
    for i in range(1,num+1):
        a*=i
    return a
print(main(10))

from functools import reduce
def main(num):
    print("方法二：导入functools中的reduce")
    return reduce(lambda x,y:x*y,range(1,num+1))
print(main(10))

import math
def main(num):
    return math.factorial(num)
print(main(5))

def main(num):
    def factorial(n):
        if n==1:
            return 1
        else:
            return factorial(n-1)*n
    return factorial(num)
print(main(5))

def main(num):
	return eval('*'.join(map(str,range(1,num+1))))
print(main(5))