Remove the last part of string separated with dot in Python

Question

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'

Answer 1

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.

Answer 2

Use rsplit to split from the end, limit to 1 split:

your_string.rsplit('.', 1)