How to get all the indexes of leading zeroes using regex in python

Question

Using Regex in Python (library re (only)), I want to create a function that gives me the position of all leading 0s in a string.

For example, if the string was: My house has 01 garden and 003 rooms.
I would want me the function to return 13, 27 and 28.

I tried for example:

import re
string = "My house has 01 garden and 003 rooms."
pattern = "(0+)[1-9]d*"

print(re.findall(pattern,string))

Obviously, the output gives me the matches but no position…

Asked By: Katharina Böhm

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Source

Answer 1

You can do the following:

import re

text = "My house has 01 garden and 003 rooms."
pattern = re.compile(r"b0+")


def leading_zeros_index(s: str) -> list:
    return [i for m in pattern.finditer(s) for i in range(m.start(), m.end())]


print(leading_zeros_index(text))

output:

[13, 27, 28]

Basically you use .finditer() in order to get the match object, then you create a range() object from match object’s .start() and .end().

I used b0+ as the pattern. There is no need to check the other characters come after zeros. b is word boundary, here means, zeros should be at the start of the words.

Answered By: S.B

How to get all the indexes of leading zeroes using regex in python

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