Python internals: adding a new statement to Python

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]

來自 “ ITPUB部落格 ” ，連結：http://blog.itpub.net/301743/viewspace-719756/，如需轉載，請註明出處，否則將追究法律責任。