Finding multiple occurrences of a string within a string in Python

Question

How do I find multiple occurrences of a string within a string in Python? Consider this:

>>> text = "Allowed Hello Hollow" >>> text.find("ll") 1 >>>  

So the first occurrence of ll is at 1 as expected. How do I find the next occurrence of it?

Same question is valid for a list. Consider:

>>> x = ['ll', 'ok', 'll'] 

How do I find all the ll with their indexes?

Answer 1

Using regular expressions, you can use re.finditer to find all (non-overlapping) occurences:

>>> import re >>> text = 'Allowed Hello Hollow' >>> for m in re.finditer('ll', text):          print('ll found', m.start(), m.end())  ll found 1 3 ll found 10 12 ll found 16 18 

Alternatively, if you don't want the overhead of regular expressions, you can also repeatedly use str.find to get the next index:

>>> text = 'Allowed Hello Hollow' >>> index = 0 >>> while index < len(text):         index = text.find('ll', index)         if index == -1:             break         print('ll found at', index)         index += 2 # +2 because len('ll') == 2  ll found at  1 ll found at  10 ll found at  16 

This also works for lists and other sequences.