Given an array of characters chars, compress it such that consecutive duplicate characters are replaced with the character followed by the count of duplicates. If the count is 1, omit it.

compress.py

from itertools import groupby

def compress(items):
    if not items:
        return []
    
    result = []
    for item, group in groupby(items):
        group_length = sum(1 for _ in group)
        result.append(item)
        if group_length > 1:
            result.append(f"{group_length}")
    
    return result

print(compress(["a", "a", "b", "b", "c", "c", "c"]))