Python: Format a number of bytes into a human readable format (non looping solution)

format_bytes_1.py

def format_bytes(num, suffix='B'):
    magnitude = int(math.floor(math.log(num, 1024)))
    val = num / math.pow(1024, magnitude)
    if magnitude > 7:
        return '{:.1f}{}{}'.format(val, 'Yi', suffix)
    return '{:3.1f}{}{}'.format(val, ['', 'Ki', 'Mi', 'Gi', 'Ti', 'Pi', 'Ei', 'Zi'][magnitude], suffix)