Update failure in python google app engine -

i have installed google app engine sdk python in ubuntu-15.04. working fine localhost. there error arise given command.

$ dev_appserver.py . info     2015-07-21 06:18:19,221 api_server.py:205] starting api server at: http://localhost:55916 info     2015-07-21 06:18:19,224 dispatcher.py:197] starting module "default" running at: http://localhost:8080 info     2015-07-21 06:18:19,236 admin_server.py:118] starting admin server at: http://localhost:8000 info     2015-07-21 06:19:49,695 module.py:809] default: "get / http/1.1" 200 13 

everything working fine till now.

when want update it, give error

$ appcfg.py update . usage: appcfg.py [options] update <directory> | [file, ...]  appcfg.py: error: expected -a app_id when application property in file app.yaml not set 

what mean?can me fix error?if there problem of app id how app id? .

the last line of second dump telling 'application property' in config file app.yaml not set. add line in beginning this:

application: <name> 

where <name> replaced application name. can update using appcfg -a tag:

appcfg.py -a <name> update <directory> 

, again replacing <name> , <directory> desired application name , project directory app.yaml file exists.