Return the next name that numerically follows `old`

def get_next_name(old, fmt='%i'):
    """Return the next name that numerically follows `old`"""
    nums = re.findall('\d+', old)
    if not nums:
        raise ValueError("Could not get the next name because the old name "
                         "has no numbers in it")
    num0 = nums[-1]
    num1 = str(int(num0) + 1)
    return old[::-1].replace(num0[::-1], num1[::-1], 1)[::-1]