Tkinter command parameters

[Gustavo Cordova]

> 
> When I try to pass an argument to a button's function, it executes the
> function
> upon loading rather than when the button is pressed.  When the button
> is pressed nothing happens.
> 
> the code is something like this:
> 
> self.mybutton = Button(parent, command = func(1))
> self.mybutton.grid()
> 
> def func(number):
> 	print str(number)
> 
> What am I doing wrong?
> 

Because, with ''' command = func(1) ''' you're assigning to "command"
the result of calling "func" with an argument "1"; consider the parenthesis
a "call" operation.

What you need is to set "command" to a reference of the function
you want called whenever the button is pressed. Also, if you want
to defer calling "func" with an argumento "1", you need to create
a function without arguments which will in turn call "func(1)".

You can do that with:

def _(): func(1)
self.mybutton = Button(parent, command = _)

(I'm using "_" as a throwaway function name)

Or, also with lambda:

self.mybutton = Button(parent, command = lambda : func(1))

-gustavo