一个Python程序员的进化（转载）

不久前，在互联网上出现了一篇有趣的文章，讲的是对于同一个问题，不同层次的Python程序员编出的Python代码显示出了不同的风格，代码都很简单，有趣。
编程新手

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

一年编程经验(学Pascal的)

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

一年编程经验(学C的)

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

一年编程经验(读过 SICP)

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

一年编程经验(Python)

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)

更懒的Python程序员

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

Python 专家

fact = lambda x: reduce(int.__mul__, xrange(2, x + 1), 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

from c_math import fact  
print fact(6) 

大英帝国程序员

   from c_maths import fact  
print fact(6)

Web 设计人员

def factorial(x):  
#-------------------------------------------------  
        #--- Code snippet from The Math Vault          ---  
        #--- Calculate factorial (C) Arthur Smith 1999 ---  
       #-------------------------------------------------  
       result = str(1)  
       i = 1 #Thanks Adam  
       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)

企业级程序员

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))