Python Consecutive characters

[TomToad]

You can do this with regular expressions

import re
regex = re.compile(r'((.)\2*)')

matches = regex.finditer("aaaabbbccddddddddeee")
s = ""
for match in matches:
    if len(match.group(0)) > 3:
        s += str(len(match.group(0)))+"Z"+match.group(0)[0]
    else:
        s += match.group(0)

print(s)