Addition of specific example of great code from one of the listed repositories.

从 Reading Code 部分和链接的 howdoi/howdoi.py 示例开始。起草一份正式说明，解释 issue 中描述的 Python 2/3 import 处理、控制流和一致的 API，然后将其添加到适当的页面中。当示例及其教学要点包含在一个 pull request 中时，即视为完成。

I absolutely love the Reading Code section, and I've been going through some of the repositories and identifying specific examples of why the code is good.

I was hoping to add one such example to the page. Specifically, from howdoi. It's virtually at the top of the codebase and it deals with standardizing the repository for Python 2 and 3.

https://github.com/gleitz/howdoi/blob/master/howdoi/howdoi.py

# Handle imports for Python 2 and 3
if sys.version < '3':
    import codecs
    from urllib import quote as url_quote
    from urllib import getproxies

    # Handling Unicode: http://stackoverflow.com/a/6633040/305414
    def u(x):
        return codecs.unicode_escape_decode(x)[0]
else:
    from urllib.request import getproxies
    from urllib.parse import quote as url_quote

    def u(x):
        return x

I think that there are two (and a half) key pedagogical takeaways from this.

The half takeaway is that supporting different versions of Python need not be a grueling task.

The remaining two are -

1. Appropriate use of control flow for module imports and function creation
2. Standardizing an API so that its source is indistinguishable to the rest of the code and functionality is consistent.

I haven't formally written this up yet, but if you think it would be a useful example, I can do that and submit a pull request.