need help about time.sleep, timer

[Sinan Nalkaya]

hello,
i need a function like that,
wait 5 seconds:
    (during wait) do the function
but function waits for keyboard input so if you dont enter any it waits 
forever.
i tried time.sleep() but when i used time.sleep in while, the function 
in while never executed.
then i found something about Timer but couldnt realize any algorithm in 
my mind.
i`ll use the function like remote controller. as you know in remote 
controllers, tv waits you for second number input. if you dont press 
any, executes the first number that you have entered.
thanks.