may i know how to run python .py file with arguments

I would like to know how to run python .py file where it has main method taking inputfilename and outputfilename as arguments
main methid should be run while i enters .pyin cmd prompt

Set path to the directory where Python is installed
My Computer(Right Click)->Properties->Advanced Settings->Environmental Variables->PATH->Edit
Set to the directory where Python is installed In my case it is C:\Python27\ . This should make pythn command usable in cmd prompt. As for your 1st part i did not understand.

As for arguments you can give the arguments and then use them in your program as sys.argv[1] as 1st argument sys.argv[2] as 2nd argument. Example Try this simple piece of code
import sys print sys.argv[1].(Note sys.argv[0] is the command itself similar to argument handling in C)