#不带==的解码
def safe_base64_decode(s):
    #若是bytes
    if isinstance(s,bytes):
        #将bytes转换成str
      s =str(s,encoding = "utf-8")
    #计算长度
    yu = len(s)%4
    return base64.b64decode(s+"="*yu)

# 测试:
assert b'abcd' == safe_base64_decode(b'YWJjZA=='), safe_base64_decode('YWJjZA==')
assert b'abcd' == safe_base64_decode(b'YWJjZA'), safe_base64_decode('YWJjZA')
print('Pass')