Count the number of occurrences in a string over consumption

countOccurrences.py

# python 3

def span(string, char):
    i = 0
    while i < len(string) and string[i] == char:
        i += 1
    return string[0:i], string[i:]


def count_occurrences(string):
    if string:
        print(len(span(string, string[0])[0]), string[0], sep='', end='')
        count_occurrences(span(string, string[0])[1])
    else:
        print()
        
count_occurrences('aaaaabbbbccccccaaaaaaa') # '5a4b6c7a'

# not my solution but very concise (https://www.linkedin.com/groups/25827/25827-6166706414627627011)
import itertools as it
"".join(str(sum(1 for _ in j))+i for i,j in it.groupby('5a4b6c7a')) #'5a4b6c7a'