Counting how many times a condition is met in Python

In python, I sometimes write a while statement like

i = 0
while <condition that involves i>:
    i += 1

The goal is, of course, to check the number of time the condition is true.
I was wondering if there’s a more simple, pythonic way to do it ? something like i = while <condition that involves i>, maybe with the walrus operator ?

Here’s a more concrete example:

def get_word_num_with_character_index(string: str, index: int) -> int:
    returns the number of the word containing a character, specified by an index

    :param string: the string to analyze
    :param index: the index of the character
    :return: the number of the word containing the specified character

    split_string = string.split(" ")

    i = 0
    while len(" ".join(split_string(:i))) <= index:
        i += 1

    return i - 1

print(get_word_num_with_character_index("jean de la fontaine", 8))
# prints 2, the index of the word containing the 8th character

How to simplify it ?