Python - Locating the position of a regex match in a string?

Question

I\'m currently using regular expressions to search through RSS feeds to find if certain words and phrases are mentioned, and would then like to extract the text on either si

Answer 1

You could use .find("is"), it would return position of "is" in the string

or use .start() from re

>>> re.search("is", String).start()
2

Actually its match "is" from "This"

If you need to match per word, you should use \b before and after "is", \b is the word boundary.

>>> re.search(r"\bis\b", String).start()
5
>>>

for more info about python regular expressions, docs here

Answer 2

re.Match objects have a number of methods to help you with this:

>>> m = re.search("is", String)
>>> m.span()
(2, 4)
>>> m.start()
2
>>> m.end()
4

Answer 3

I don't think this question has been completely answered yet because all of the answers only give single match examples. The OP's question demonstrates the nuances of having 2 matches as well as a substring match which should not be reported because it is not a word/token.

To match multiple occurrences, one might do something like this:

iter = re.finditer(r"\bis\b", String)
indices = [m.start(0) for m in iter]

This would return a list of the two indices for the original string.