一个Python程序员的进化

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。下面让我们一起来看看一个Python程序员是进阶的全过程。

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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:
        resultresult = result * i
        ii = 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))

自己还是初学者

一年编程经验(读过 SICP)  用的是尾递归

Python 专家

fact = lambda x: reduce(int.__mul__, xrange(2, x + 1), 1)
print fact(6)

用的是reduce.

学习到：

xrange([start], stop[, step])

This function is very similar to range(), but returns an “xrange object” instead of a list. This is an opaque sequence type which yields the same values as the corresponding list, without actually storing them all simultaneously. The advantage of xrange() over range() is minimal (since xrange() still has to create the values when asked for them) except when a very large range is used on a memory-starved machine or when all of the range’s elements are never used (such as when the loop is usually terminated with break).

 

 

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