pymongo连接mongodb鉴权失败

报错信息：

xmlrpclib.Fault: <Fault 1: "<class 'pymongo.errors.OperationFailure'>:command SON([('saslStart', 1), ('mechanism', 'SCRAM-SHA-1'), ('payload', Binary('n,,n=admin,r=NDkzNDIzMzI3OTY1', 0)), ('autoAuthorize', 1)]) on namespace malware_detection_cache.$cmd failed: Authentication failed.">

解决方法：

 在Mongodb 4 中增加authSource信息，解决方法如下

client = MongoClient(host=<<hostname>>,
                     port=<<port>>, 
                     username=<<user_name>>, 
                     password=<<password>>,
                    authSource="admin")
db_obj = client[db_name]