{{ user:username }} not always returning right username

[NeitruptNep]

I am using Pyro CMS and implementing its custom module.In this module when I am to get the user name by \[code\]{{user:username}}\[/code\] it returns wrong value.So I want to ask that is it correct way to get username or here is any error.I there any other way to get the username in pyroCMS.Thanks.