当else做得最多的时候，最有效的方式来执行if-elif-elif-else语句吗？

Question

我有一条if-elif-elif-else语句，其中99％的时间执行else语句：if something == 'this':    doThis()elif something == 'that':    doThat()elif something == 'there':    doThere()else:    doThisMostOfTheTime()这个构造完成了很多，但是由于它在碰到其他情况之前会遍历所有条件，所以我觉得这不是很有效，更不用说Pythonic了。另一方面，它确实需要知道是否满足任何这些条件，因此无论如何都应该对其进行测试。是否有人知道是否以及如何才能更有效地完成此工作，或者这仅仅是做到这一点的最佳方法？

Answer 1

你可以使用pypy吗？

保留原始代码，但在pypy上运行可使我的速度提高50倍。

CPython：

matt$ python

Python 2.6.8 (unknown, Nov 26 2012, 10:25:03)

[GCC 4.2.1 Compatible Apple Clang 3.0 (tags/Apple/clang-211.12)] on darwin

Type "help", "copyright", "credits" or "license" for more information.

>>>

>>> from timeit import timeit

>>> timeit("""

... if something == 'this': pass

... elif something == 'that': pass

... elif something == 'there': pass

... else: pass

... """, "something='foo'", number=10000000)

1.728302001953125

pypy：

matt$ pypy

Python 2.7.3 (daf4a1b651e0, Dec 07 2012, 23:00:16)

[PyPy 2.0.0-beta1 with GCC 4.2.1] on darwin

Type "help", "copyright", "credits" or "license" for more information.

And now for something completely different: ``a 10th of forever is 1h45''

>>>>

>>>> from timeit import timeit

>>>> timeit("""

.... if something == 'this': pass

.... elif something == 'that': pass

.... elif something == 'there': pass

.... else: pass

.... """, "something='foo'", number=10000000)

0.03306388854980469