Python Compression Run Length encoding

Question

I am trying to learn about run length encoding and I found this challenge online that I cant do. It requires you to write a compression function called compression(strg) that takes a binary string strg of length 64 as input and returns another binary string as output. The output binary string should be a run-length encoding of the input string.

compression('1010101001010101101010100101010110101010010101011010101001010101')

'1010101001010101*4'

Here is what I have, but this does NOT find the pattern:

from itertools import *

def compression(strg):
    return [(len(list(group)),name) for name, group in groupby(strg)]

I need some help solving this.

Answer 1

I believe that you are conflating RLE with Lempel/Ziv sliding window compression.

RLE strictly works on repeated characters: WWWWWWWW => W8

LZ has a sliding window that will pick up patterns as you describe.

David MacKay's site has example compression codes in Python, including LZ