删除Python中用点分隔的字符串的最后一部分 [英] Remove the last part of string separated with dot in Python

问题描述

如何以优雅的方式转换字符串，例如:

'test.test1.test2''test.test3.test4'

变成这样的字符串:

'test.test1''test.test3'

解决方案

这里不需要正则表达式.

使用 str.rsplit():

output = inputstr.rsplit('.', 1)[0]

或str.rpartition():

output = inputstr.rpartition('.')[0]

str.rpartition() 是两者中速度更快的，但您需要 Python 2.5 或更新版本.

演示:

<预><代码>>>>'test.test1.test2'.rsplit('.', 1)[0]'test.test1'>>>'test.test1.test2'.rpartition('.')[0]'test.test1'>>>'test.test3.test4'.rsplit('.', 1)[0]'test.test3'>>>'test.test3.test4'.rpartition('.')[0]'test.test3'

与一百万次运行的时间比较:

<预><代码>>>>从时间导入时间>>>timeit("s.rsplit('.', 1)[0]", "s = 'test.test1.test2'")0.5848979949951172>>>timeit("s.rpartition('.')[0]", "s = 'test.test1.test2'")0.27417516708374023

您可以以 100 万次 str.rsplit() 的价格运行 200 万次 str.rpartition() 调用.

How is it possible to convert in elegant way strings like:

'test.test1.test2'
'test.test3.test4'

into strings like these:

'test.test1'
'test.test3'

解决方案

No need for regular expressions here.

Use str.rsplit():

output = inputstr.rsplit('.', 1)[0]

or str.rpartition():

output = inputstr.rpartition('.')[0]

str.rpartition() is the faster of the two but you need Python 2.5 or newer for it.

Demo:

>>> 'test.test1.test2'.rsplit('.', 1)[0]
'test.test1'
>>> 'test.test1.test2'.rpartition('.')[0]
'test.test1'
>>> 'test.test3.test4'.rsplit('.', 1)[0]
'test.test3'
>>> 'test.test3.test4'.rpartition('.')[0]
'test.test3'

And a time comparison against a million runs:

>>> from timeit import timeit
>>> timeit("s.rsplit('.', 1)[0]", "s = 'test.test1.test2'")
0.5848979949951172
>>> timeit("s.rpartition('.')[0]", "s = 'test.test1.test2'")
0.27417516708374023

where you can run 2 million str.rpartition() calls for the price of 1 million str.rsplit()'s.

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