Can I remove all the letters from a string and keep just the numbers?

Question

I'm working in python 2.6 and I would like to take "gpmetisfile.txt.part.4" and return just the number 4. (Ordinarily I would just lop off and save the end value, but its length and arrangement may change in the future and I would rather be safe and just obtain the numbers, in order, from the string itself).

There was a question similar to mine in 2009, but the answers were conflicting.

Thanks in advance.

See [answer](http://stackoverflow.com/questions/4289331/extract-numbers-of-a-string) by fmark. — Ryan, Jun 22 '12 at 17:56

score 3 · Accepted Answer · answered Jun 22 '12 at 17:57

3

The following does what your question answer says: removes everything but the numbers. Is that what you need?

In [1]: s = 'gpmetisfile.txt.part.4'

In [2]: import re

In [3]: re.sub('\D', '', s)
Out[3]: '4'

The reason why I ask is that, for instance, 'gpmetisfile.txt.06_2012.part.4' will become '0620124'.

answered Jun 22 '12 at 17:57

Lev Levitsky

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This is exactly what I need. Only one number will appear in the string, ie now my file is "gpmetis.part.1205.txt". Thank you for checking. – Ason Jun 22 '12 at 18:06

score 3 · Answer 2 · answered Jun 22 '12 at 19:23

3

>>> s = 'as!das42!fsd'
>>> ''.join(filter(str.isdigit, s))
'42'

answered Jun 22 '12 at 19:23

Aleksei astynax Pirogov

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Great! this also works. Is there a benefit of using one method over another? – Ason Jun 22 '12 at 19:41
@AllysonKim, this solution is two times faster than regex :) Regular expressions are good for complex text processing, but are overkill in this case, IMHO – Aleksei astynax Pirogov Jun 23 '12 at 04:11
Thank you! I wish I could select both answers. – Ason Jun 25 '12 at 18:23

Can I remove all the letters from a string and keep just the numbers?

2 Answers2