TkInter buttons - callback (command) function

[erasmus]

It seems that in some cases the callback (command) function in a TkInter Button runs automatically when drawn for the first time. Example:
b=Button(frame, text="Click me",command=myFunction())
b.pack()
..
so, myFunction() executes when the screen is drawn for the first time.
But (!) if I do not include the "()" after myFunction, then it does not run until it is explicitly clicked. IE:
b=Button(frame, text="Click me", command=myFunction)
..
In this case myFunction does not run until clicked.
Is this correct behavior? It seems strange to me, and I do not find it documented anywhere.
(I am using a very recent version of python/tkinter on XP)
Thanks!
Erasmus

[erasmus]

oops. I see whats going on .. obviously: Python calls the function and returns the result to command. So is there any way to send parameters directly in a callback function?

It seems that in some cases the callback (command) function in a TkInter Button runs automatically when drawn for the first time. Example:
b=Button(frame, text="Click me",command=myFunction())
b.pack()
..
so, myFunction() executes when the screen is drawn for the first time.
But (!) if I do not include the "()" after myFunction, then it does not run until it is explicitly clicked. IE:
b=Button(frame, text="Click me", command=myFunction)
..
In this case myFunction does not run until clicked.
Is this correct behavior? It seems strange to me, and I do not find it documented anywhere.
(I am using a very recent version of python/tkinter on XP)
Thanks!
Erasmus

[ilikepython]

oops. I see whats going on .. obviously: Python calls the function and returns the result to command. So is there any way to send parameters directly in a callback function?

Do you mean like this:?

but = Button(text = "Press", command = lambda x = "blah": myFunction(x))
 

Notice that the function doesn't get called right away, it is in the body of the lambda.