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148 lines
4.5 KiB
Markdown
148 lines
4.5 KiB
Markdown
# Python 简介
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## **Python** 历史
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`Python` 的创始人为荷兰人吉多·范罗苏姆（`Guido van Rossum`）。1989年的圣诞节期间，吉多·范罗苏姆为了在阿姆斯特丹打发时间，决心开发一个新的脚本解释程序，作为 ABC 语言的一种继承。之所以选中 `Python` 作为程序的名字，是因为他是 BBC 电视剧——蒙提·派森的飞行马戏团（`Monty Python's Flying Circus`）的爱好者。
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1991年，第一个 Python 编译器诞生。它是用C语言实现的，并能够调用C语言的库文件。
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`Python 2.0` 于 2000 年 10 月 16 日发布，增加了实现完整的垃圾回收，并且支持 `Unicode`。
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`Python 3.0` 于 2008 年 12 月 3 日发布，此版不完全兼容之前的 `Python` 源代码。不过，很多新特性后来也被移植到旧的 `Python 2.6/2.7` 版本。
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## 第一行Python代码
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安装好 `Python` 之后，在命令行下输入：
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```py
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python
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```
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就可以进入 `Python` 解释器的页面。
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按照惯例，第一行代码应该是输出 `"hello world!"`：
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In [1]:
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```py
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print "hello world!"
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```
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```py
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hello world!
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```
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相对与 `Java，C` 等语言，`Python` 仅仅使用一行语句就完成的了这个任务。
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可以将这句话的内容保存到一个文本文件中，并使用后缀名 `.py` 结尾，例如 `hello_world.py`，在命令行下运行这个程序：
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```py
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python hello_world.py
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```
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也会输出 `"hello world!"` 的结果。
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## Python 之禅
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在 **Python** 解释器下输入
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`import this`
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会出来这样一首小诗：
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In [2]:
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```py
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import this
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```
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```py
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The Zen of Python, by Tim Peters
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Beautiful is better than ugly.
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Explicit is better than implicit.
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Simple is better than complex.
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Complex is better than complicated.
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Flat is better than nested.
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Sparse is better than dense.
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Readability counts.
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Special cases aren't special enough to break the rules.
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Although practicality beats purity.
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Errors should never pass silently.
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Unless explicitly silenced.
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In the face of ambiguity, refuse the temptation to guess.
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There should be one-- and preferably only one --obvious way to do it.
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Although that way may not be obvious at first unless you're Dutch.
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Now is better than never.
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Although never is often better than *right* now.
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If the implementation is hard to explain, it's a bad idea.
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If the implementation is easy to explain, it may be a good idea.
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Namespaces are one honking great idea -- let's do more of those!
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```
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这首诗反映了**Python**的设计哲学——**Python**是一种追求优雅，明确，简单的编程语言，但事实上，产生这首诗的代码并没有写的那么简单易懂：
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In [3]:
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```py
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s = """Gur Mra bs Clguba, ol Gvz Crgref
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Ornhgvshy vf orggre guna htyl.
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Rkcyvpvg vf orggre guna vzcyvpvg.
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Fvzcyr vf orggre guna pbzcyrk.
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Pbzcyrk vf orggre guna pbzcyvpngrq.
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Syng vf orggre guna arfgrq.
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Fcnefr vf orggre guna qrafr.
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Ernqnovyvgl pbhagf.
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Fcrpvny pnfrf nera'g fcrpvny rabhtu gb oernx gur ehyrf.
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Nygubhtu cenpgvpnyvgl orngf chevgl.
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Reebef fubhyq arire cnff fvyragyl.
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Hayrff rkcyvpvgyl fvyraprq.
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Va gur snpr bs nzovthvgl, ershfr gur grzcgngvba gb thrff.
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Gurer fubhyq or bar-- naq cersrenoyl bayl bar --boivbhf jnl gb qb vg.
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Nygubhtu gung jnl znl abg or boivbhf ng svefg hayrff lbh'er Qhgpu.
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Abj vf orggre guna arire.
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Nygubhtu arire vf bsgra orggre guna *evtug* abj.
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Vs gur vzcyrzragngvba vf uneq gb rkcynva, vg'f n onq vqrn.
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Vs gur vzcyrzragngvba vf rnfl gb rkcynva, vg znl or n tbbq vqrn.
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Anzrfcnprf ner bar ubaxvat terng vqrn -- yrg'f qb zber bs gubfr!"""
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d = {}
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for c in (65, 97):
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for i in range(26):
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d[chr(i+c)] = chr((i+13) % 26 + c)
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print "".join([d.get(c, c) for c in s])
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```
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```py
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The Zen of Python, by Tim Peters
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Beautiful is better than ugly.
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Explicit is better than implicit.
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Simple is better than complex.
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Complex is better than complicated.
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Flat is better than nested.
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Sparse is better than dense.
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Readability counts.
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Special cases aren't special enough to break the rules.
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Although practicality beats purity.
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Errors should never pass silently.
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Unless explicitly silenced.
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In the face of ambiguity, refuse the temptation to guess.
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There should be one-- and preferably only one --obvious way to do it.
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Although that way may not be obvious at first unless you're Dutch.
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Now is better than never.
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Although never is often better than *right* now.
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If the implementation is hard to explain, it's a bad idea.
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If the implementation is easy to explain, it may be a good idea.
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Namespaces are one honking great idea -- let's do more of those!
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```
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> Life is short. Use Python. |