String splitting in Python using regex

Question

I'm trying to split a string in Python so that I get everything before a certain regex.

example string: "Some.File.Num10.example.txt"

I need everything before this part: "Num10", regex: r'Num\d\d' (the number will vary and possibly what comes after).

Any ideas on how to do this?

score 13 · Accepted Answer · edited May 11 '12 at 08:39

13

>>> import re
>>> s = "Some.File.Num10.example.txt"
>>> p = re.compile("Num\d{2}")
>>> match = p.search(s)
>>> s[:match.start()]
'Some.File.'

This would be more efficient that doing a split because search doesn't have to scan the whole string. It breaks on the first match. In your example it wouldn't make a different as the strings are short but in case your string is very long and you know that the match is going to be in the beginning, then this approach would be faster.

I just wrote a small program to profile search() and split() and confirmed the above assertion.

edited May 11 '12 at 08:39

kragniz

305
1
12

answered May 10 '12 at 23:40

varunl

19,499
5
29
47

You can use `p = re.compile("Num\d")` simply as number can be anything so we are just concerned when it starts in the string. – theharshest May 11 '12 at 06:57

score 10 · Answer 2 · answered May 10 '12 at 23:34

10

>>> import re
>>> text = "Some.File.Num10.example.txt"
>>> re.split(r'Num\d{2}',text)[0]
'Some.File.'

answered May 10 '12 at 23:34

jamylak

128,818
30
231
230

score 5 · Answer 3 · edited May 12 '12 at 01:20

5

You can use Python's re.split()

import re

my_str = "This is a string."

re.split("\W+", my_str)

['This', 'is', 'a', 'string', '']

edited May 12 '12 at 01:20

octopusgrabbus

10,555
15
68
131

answered May 10 '12 at 23:29

Ignacio Vazquez-Abrams

776,304
153
1,341
1,358

String splitting in Python using regex

3 Answers3

Linked