python - Python 中的阶乘函数

Question

我是 Python 的新手，正在学习语法和各种功能。我想知道是否

x=reduce((lambda x,y: x*y) , [x for x in range(5) if x > 0])

是计算数字阶乘的正确函数吗？

亲切的问候

Answer 1

类似于 http://www.willamette.edu/~fruehr/haskell/evolution.html 的内容

# beginner

def fac(n):
    f = 1
    i = 1
    while i <= n:
        f *= i
        i += 1
    return f

# advanced beginner

def fac(n):
    return n * fac(n - 1) if n > 1 else 1

# intermediate

def fac(n):
    return reduce(lambda x, y: x * y, range(1, n + 1))

# advanced intermediate

import operator
def fac(n):
    return reduce(operator.mul, xrange(1, n + 1))

# professional

import math
print math.factorial(5)

# guru

import scipy.misc as sc
print sc.factorial(5, exact=True)