Python strings are missing a findall function analog to find

Question

Python strings appear to be missing a function that returns the index of all matches.

There is a re.findall() in the Python module that supplies the power of regular expressions within the standard library. But using the re module to find all occurrences of one string in another seems excessive to me. There's no need for regular expressions in this case.

Answer 1

One solution is a custom findall() function to that finds all occurrences of a string. It is a mix of the methods of the re.findall() and the str.find() method and returns a list indexes where all the matches start.

from typing import Optional

def findall(
    pattern: str, string: str, start: Optional[int] = None, end: Optional[int] = None
):
    """Find all matches of a pattern in a string.

    Arguments
    ---------
    pattern : str
        The string to find.
    string : str
        The string to search in.
    start : int or None
        Where in the string to start the search for matches.
    end : int or None
        Where in the string to end the search for matches.
    
    Returns
    -------
    list
        A list of of the index of the start of all matches.
        If no matches are found the list is empty.
    """

    i = string.find(pattern, start, end)

    if i == -1:
        return []
    else:
        return [i] + findall(pattern, string, i + 1, end)