python源码解析0：趣事

About 两处python源码的趣味解读。

The Zen of Python

我们知道，import this会打印如下“蟒蛇之禅”：

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The Zen of Python, by Tim Peters

Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Complex is better than complicated.
Flat is better than nested.
Sparse is better than dense.
Readability counts.
Special cases aren't special enough to break the rules.
Although practicality beats purity.
Errors should never pass silently.
Unless explicitly silenced.
In the face of ambiguity, refuse the temptation to guess.
There should be one-- and preferably only one --obvious way to do it.
Although that way may not be obvious at first unless you're Dutch.
Now is better than never.
Although never is often better than *right* now.
If the implementation is hard to explain, it's a bad idea.
If the implementation is easy to explain, it may be a good idea.
Namespaces are one honking great idea -- let's do more of those!

但是在source里面也就是2.7/Lib/this.py里，是这样的：

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s = """Gur Mra bs Clguba, ol Gvz Crgref

Ornhgvshy vf orggre guna htyl.
Rkcyvpvg vf orggre guna vzcyvpvg.
Fvzcyr vf orggre guna pbzcyrk.
Pbzcyrk vf orggre guna pbzcyvpngrq.
Syng vf orggre guna arfgrq.
Fcnefr vf orggre guna qrafr.
Ernqnovyvgl pbhagf.
Fcrpvny pnfrf nera'g fcrpvny rabhtu gb oernx gur ehyrf.
Nygubhtu cenpgvpnyvgl orngf chevgl.
Reebef fubhyq arire cnff fvyragyl.
Hayrff rkcyvpvgyl fvyraprq.
Va gur snpr bs nzovthvgl, ershfr gur grzcgngvba gb thrff.
Gurer fubhyq or bar-- naq cersrenoyl bayl bar --boivbhf jnl gb qb vg.
Nygubhtu gung jnl znl abg or boivbhf ng svefg hayrff lbh'er Qhgpu.
Abj vf orggre guna arire.
Nygubhtu arire vf bsgra orggre guna *evtug* abj.
Vs gur vzcyrzragngvba vf uneq gb rkcynva, vg'f n onq vqrn.
Vs gur vzcyrzragngvba vf rnfl gb rkcynva, vg znl or n tbbq vqrn.
Anzrfcnprf ner bar ubaxvat terng vqrn -- yrg'f qb zber bs gubfr!"""

d = {}
for c in (65, 97):
    for i in range(26):
        d[chr(i+c)] = chr((i+13) % 26 + c)

print "".join([d.get(c, c) for c in s])

哈哈，这不就是凯撒密码么。。。每个字母分大小写(65:A, 97:a)都被对应到ASCII 表后13个位置，于是就有

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{'A': 'N',
 'B': 'O',
 'C': 'P',
 'D': 'Q',
 'E': 'R',
 'F': 'S',
....
's': 'f',
 't': 'g',
 'u': 'h',
 'v': 'i',
 'w': 'j',
 'x': 'k',
 'y': 'l',
 'z': 'm'}

所以，原作者应该是这样写出来的密码的

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s = """The Zen of Python, by Tim Peters

Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Complex is better than complicated.
Flat is better than nested.
Sparse is better than dense.
Readability counts.
Special cases aren't special enough to break the rules.
Although practicality beats purity.
Errors should never pass silently.
Unless explicitly silenced.
In the face of ambiguity, refuse the temptation to guess.
There should be one-- and preferably only one --obvious way to do it.
Although that way may not be obvious at first unless you're Dutch.
Now is better than never.
Although never is often better than *right* now.
If the implementation is hard to explain, it's a bad idea.
If the implementation is easy to explain, it may be a good idea.
Namespaces are one honking great idea -- let's do more of those!"""

d = {}
for c in (65, 97):
    for i in range(26):
        d[chr(i+c)] = chr((i-13) % 26 + c)

print("".join([d.get(c, c) for c in s]))

很神奇吧？哈哈，其实就是逆向一下就ok😎

antigravity

我们知道，在python里，import antigravity会让我们弹到一个网站，里面有这幅著名的图画

python带我们飞！那么为什么会这样呢？

看看源码，

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import webbrowser

webbrowser.open("http://xkcd.com/353/")

哈哈，原来就这两行，Are you kidding me?

关于这个的来龙去脉，可以看看这里：The History of Python: import antigravity以及这里：import antigravity | sciyoshi.com，大意是源自google的一个复活节彩蛋。值得注意的是，python3的antigravity彩蛋升级了！不信你看

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import webbrowser
import hashlib

webbrowser.open("https://xkcd.com/353/")

def geohash(latitude, longitude, datedow):
    '''Compute geohash() using the Munroe algorithm.

    >>> geohash(37.421542, -122.085589, b'2005-05-26-10458.68')
    37.857713 -122.544543

    '''
    # http://xkcd.com/426/
    h = hashlib.md5(datedow).hexdigest()
    p, q = [('%f' % float.fromhex('0.' + x)) for x in (h[:16], h[16:32])]
    print('%d%s %d%s' % (latitude, p[1:], longitude, q[1:]))

里面隐藏了一个计算Geohashing的算法，可以根据给定点坐标的经纬度以及当前时间计算一个随机的新的点坐标。