Python 2.7, how can I find the position of group of letters in a string?

Question

I need to know how can I find ALL the position of a group of letters in a string. For example, in the string "Canyoucanacanasacannercancanacan" the letters "an" recur 7 times. I want to know the exact position of each one, possibly in a list. How can I do?

Thank you!

Answer 1

Surprisingly I couldn't find a duplicate of this question! You can do this using str.index, while updating the starting position that you're looking from to exclude parts of the string you've already checked.

s = 'Canyoucanacanasacannercancanacan'
position_list = []
i = 0
while True:
    try:
        position = s.index('an', i)
    except ValueError:
        break
    position_list.append(position)
    i = position + 1
print(position_list)

As someone suggested, you could also use str.find, like this:

s = 'Canyoucanacanasacannercancanacan'
position_list = []
i = s.find('an')
while i != -1:
    position_list.append(i)
    i = s.find('an', i+1)
print(position_list)