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Python internals: adding a new statement to Python

原创 Linux操作系统 作者:jieforest 时间:2012-03-28 17:22:11 0 删除 编辑

This article is an attempt tobetter understand how the front-end of Python works. Just reading documentationand source code may be a bit boring, so I’m taking a hands-on approach here:I’m going to add an until statement to Python.


All the coding for this article wasdone against the cutting-edge Py3k branch in the Python Mercurial repository mirror.


[size=15.0pt]The[size=15.0pt] [size=15.0pt]until[size=15.0pt] [size=15.0pt]statement[size=15.0pt]
[size=10.5pt]Some languages, like Ruby, have an until [size=10.5pt]statement, which is the complement to while [size=10.5pt](until num == 0 [size=10.5pt]is equivalent to while num != 0[size=10.5pt]). In Ruby, I can write:

CODE:

1.num = 3
2.until num == 0 do
3.puts num
4.num -= 1
5.end[size=10.5pt]And it will print:

CODE:

1.3
2.2
3.1[size=10.5pt]So, I want to add a similarcapability to Python. That is, being able to write:

CODE:

1.num = 3
2.until num == 0:
3.print(num)
4.num -= 1[size=10.5pt]

[size=10.5pt]
[size=10.5pt]

来自 “ ITPUB博客 ” ,链接:http://blog.itpub.net/301743/viewspace-719756/,如需转载,请注明出处,否则将追究法律责任。

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