How to extract numbers from a string in Python?

Question

I would like to extract all the numbers contained in a string. Which is better suited for the purpose, regular expressions or the isdigit() method?

Example:

line = "hello 12 hi 89" 

Result:

[12, 89] 

Answer 1

If you only want to extract only positive integers, try the following:

>>> txt = "h3110 23 cat 444.4 rabbit 11 2 dog" >>> [int(s) for s in txt.split() if s.isdigit()] [23, 11, 2] 

I would argue that this is better than the regex example because you don't need another module and it's more readable because you don't need to parse (and learn) the regex mini-language.

This will not recognize floats, negative integers, or integers in hexadecimal format. If you can't accept these limitations, jmnas's answer below will do the trick.

Answer 2

I'd use a regexp :

>>> import re >>> re.findall(r'\d+', 'hello 42 I\'m a 32 string 30') ['42', '32', '30'] 

This would also match 42 from bla42bla. If you only want numbers delimited by word boundaries (space, period, comma), you can use \b :

>>> re.findall(r'\b\d+\b', 'he33llo 42 I\'m a 32 string 30') ['42', '32', '30'] 

To end up with a list of numbers instead of a list of strings:

>>> [int(s) for s in re.findall(r'\b\d+\b', 'he33llo 42 I\'m a 32 string 30')] [42, 32, 30]