char_counter.py

def compression(input_str):
    def _compression(_input_str):
        i = -1
        counter = 1
        for char in _input_str:
            i += 1
            if i == 0:
                continue
            previous = _input_str[i - counter]
            if previous == char:
                counter += 1
            elif counter > 1:
                yield previous + str(counter)
                counter = 1
            else:
                yield char
        if counter > 1:
            yield _input_str[i - 1] + str(counter)
    return ''.join(_compression(input_str))

print(compression("bbbbcccrrrr  rrrr"))