python 二进制数相加

def add_binary_nums(x,y):

        max_len = max(len(x), len(y))

        x = x.zfill(max_len)

        y = y.zfill(max_len)

        result = ''

        carry =

        for i in range(max_len-, -, -):

            r = carry

            r +=  if x[i] == '' else

            r +=  if y[i] == '' else

            result = ('' if r %  ==  else '') + result

            carry =  if r <  else

        if carry != : result = '' + result

        return result.zfill(max_len)

print(add_binary_nums('', ''))

print(add_binary_nums('', ''))

print(add_binary_nums('', ''))

print(add_binary_nums('', ''))