趣文：Python程序员的进化史

导读：下面代码来自 fmeyer ，列举了各种程序员所写的阶乘算法代码，甚至包括网页设计师的。 

#新手程序员

def factorial(x):
    if x == 0:
        return 1
    else:
        return x * factorial(x - 1)
print factorial(6)

 
#有一年 Pascal 经验的程序员

def factorial(x):
    result = 1
    i = 2
    while i <= x:
        result = result * i
        i = i + 1
    return result
print factorial(6)
 

#有一年 C 经验的程序员

def fact(x): #{
    result = i = 1;
    while (i <= x): #{
        result *= i;
        i += 1;
    #}
    return result;
#}
print(fact(6))
 

#有一年 SICP 经验的程序员

@tailcall
def fact(x, acc=1):
    if (x > 1): return (fact((x - 1), (acc * x)))
    else: return acc
print(fact(6))

#有一年 Python 经验的程序员

def Factorial(x):
    res = 1
    for i in xrange(2, x + 1):
        res *= i
    return res
print Factorial(6)

 
#懒惰的Python程序员

def fact(x):
    return x > 1 and x * fact(x - 1) or 1
print fact(6)

 
#更懒惰的Python程序员

f = lambda x: x and x * f(x - 1) or 1
print f(6)

#专家级Python程序员

import operator as op
import functional as f
fact = lambda x: f.foldl(op.mul, 1, xrange(2, x + 1))
print fact(6)

 
#Python 黑客

import sys
@tailcall
def fact(x, acc=1):
    if x: return fact(x.__sub__(1), acc.__mul__(x))
    return acc
sys.stdout.write(str(fact(6)) + '\n')
 

#专家级程序员

import c_math
fact = c_math.fact
print fact(6)

 
#英国专家级程序员 （译注：在英式英语中，“数学”的简写，多用“maths”，不是“math"。）

import c_maths
fact = c_maths.fact
print fact(6)

 
#网页设计师

def factorial(x):
    #-------------------------------------------------
    #--- 这段代码是从 Math Vault 那弄过来滴---
    #--- 计算阶乘 （C）亚瑟·史密斯 1999年---
    #-------------------------------------------------
    result = str(1)
    i = 1 #谢谢亚当
    while i <= x:
        #result = result * i #It's faster to use *=
        #result = str(result * result + i)
           #result = int(result *= i) #??????
        result str(int(result) * i)
        #result = int(str(result) * i)
        i = i + 1
    return result
print factorial(6)
 

#Unix 程序员

import os
def fact(x):
    os.system('factorial ' + str(x))
fact(6)

 
#Windows 程序员

NULL = None
def CalculateAndPrintFactorialEx(dwNumber,
                                 hOutputDevice,
                                 lpLparam,
                                 lpWparam,
                                 lpsscSecurity,
                                 *dwReserved):
    if lpsscSecurity != NULL:
        return NULL #Not implemented
    dwResult = dwCounter = 1
    while dwCounter <= dwNumber:
        dwResult *= dwCounter
        dwCounter += 1
    hOutputDevice.write(str(dwResult))
    hOutputDevice.write('\n')
    return 1
import sys
CalculateAndPrintFactorialEx(6, sys.stdout, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL)

 
#企业程序员

def new(cls, *args, **kwargs):
    return cls(*args, **kwargs)
 
class Number(object):
    pass
 
class IntegralNumber(int, Number):
    def toInt(self):
        return new (int, self)
 
class InternalBase(object):
    def __init__(self, base):
        self.base = base.toInt()
 
    def getBase(self):
        return new (IntegralNumber, self.base)
 
class MathematicsSystem(object):
    def __init__(self, ibase):
        Abstract
 
    @classmethod
    def getInstance(cls, ibase):
        try:
            cls.__instance
        except AttributeError:
            cls.__instance = new (cls, ibase)
        return cls.__instance
 
class StandardMathematicsSystem(MathematicsSystem):
    def __init__(self, ibase):
        if ibase.getBase() != new (IntegralNumber, 2):
            raise NotImplementedError
        self.base = ibase.getBase()
 
    def calculateFactorial(self, target):
        result = new (IntegralNumber, 1)
        i = new (IntegralNumber, 2)
        while i <= target:
            result = result * i
            i = i + new (IntegralNumber, 1)
        return result
 
print StandardMathematicsSystem.getInstance(new (InternalBase, new (IntegralNumber, 2))).calculateFactorial(new (IntegralNumber, 6))

下面代码是kohashi给出的，他说是在邮局看到的。

#VBA 程序员
def factorial(x):
    if x == 0:
        return 1
    if x == 1:
        return x
    if x == 2:
        return x * (x-1)
    if x == 3:
        return x * (x-1) * (x-2)
    if x == 4:
        return x * (x-1) * (x-2) * (x-3)
    if x == 5:
        return x * (x-1) * (x-2) * (x-3) * (x-4)
    if x == 6:
        return x * (x-1) * (x-2) * (x-3) * (x-4) * (x-5)
print factorial(6)

原文：fmeyer    编译：伯乐在线 – 黄利民