Using Star Growth with letters in a string

Question

I have this activity where I have to use star growth in a string where it grows with the amount of a character in the string. Here is an example: star_match_growth("incandescent", "c") and have it return as: inc*andesc**ent and have it continue if there are any more c's in the string. This is what I have to far:

def star_match_growth(word, letter):
  builder = ""
  for i in range(0, len(word)):
    word_2 = word.replace(letter, str(star_growth(word.count(letter))))
  return word_2 




def star_growth(top):
  word = top * "*"
  builder = ""
  for i in range(1, len(word) + 1):
    builder += word[0:i] + " "
  return builder[:-1]

print(star_match_growth("incandescent", "c"))

and the output is:

inc* **andesc* **ent

Note it also has to ignore capitalization Note I'm also not allowed to import anything into the code iteself

Answer 1

You can provide re.sub with a callable (function, lambda, etc.) which must accept a single regex match-object as an argument, and which must return a string with which to replace that match. In my snippet, I'm taking advantage of a persistent default argument it, which is an iterator that yields ascending integers (starting at 1 in this case). The state of the iterator is preserved between invocations, which has the effect of appending more and more stars to subsequent matches:

def star_match_growth(string, pattern):
    import re
    from itertools import count

    def replace(match, it=count(1)):
        return match.group() + ("*" * next(it))

    return re.sub(pattern, replace, string, flags=re.IGNORECASE)


print(star_match_growth("incandescent", "C"))

    

Output:

inc*andesc**ent
>>> 

---

EDIT - Not taking advantage of the standard library, and using a generator that yields characters (and sometimes strings of stars):

def star_match_growth(string, letter):
    num_stars = 1
    for char in string:
        yield char
        if char in {letter.lower(), letter.upper()}:
            yield "*" * num_stars
            num_stars += 1

print("".join(star_match_growth("incandescent", "C")))