Openerp Message_post Error..nameerror: Global Name '_' Is Not Defined

I have created a custom module with chatter in the form. I want to post a custom message. but I am getting following error. File '/opt/openerp/my_modules/forum/forum.py', line 22,

Solution 1:

try this to import in your .py file

from openerp import tools

from openerp.tools.translate import _

_ is used for a translation the message when active user's language is changed according to. It's translate the message as in your .po file.