How can I get TK button commands to take in a parameter with a variable (Python)

Question

This has stumped me for over a week. As the title asks, how can I get TK button commands to take in a parameter with a variable?

Here is the exact code I'm using:

i=0

# Make a Staff list button
staffButton = Button(masterFrame,
                        text='Staff List',
                        width=20,
                        justify=LEFT,
                        #command=lambda:self.openTabHere(isLeft,STAFF_LIST_TAB))
                        command=lambda:self.openTabHere(isLeft,i))
staffButton.grid(column=0, row=1)

# Make a course list button
courseButton = Button(masterFrame,
                        text='Course List',
                        width=20,
                        justify=LEFT,
                        #command=lambda:self.openTabHere(isLeft,COURSE_LIST_TAB))
                        command=lambda:self.openTabHere(isLeft,i))
courseButton.grid(column=0, row=0)

i=1

Note that if I use the commented (hardcoded) command, it works as intended. However, if I use the code not commented, with the variable i, both buttons end up with the command for i=1.

Is it that the command gets the variable i at runtime? If so, or for some other reason, what can I do to accomplish what I'm trying to do?

This is because I do something similar for every staff member; a for loop intending to have buttons that open up a tab with a staff ID that is in the parameter as a variable that can't be hardcoded.

Thanks ahead of time.

I just tried it and found this isn't the solution. I get an invalid syntax when I try to run that. — narutoreplicate
– narutoreplicate, Commented Oct 29, 2012 at 0:59
Yes, I just noticed it was python instead of tcl, and deleted my stupid comment. Note, if you post a self-contained program instead of just the above extract others might be able to try it out and find the problem — James Waldby - jwpat7
– James Waldby - jwpat7, Commented Oct 29, 2012 at 1:01
Thanks for the tip; the main issue was that I didn't want to make a self-contained program that didn't fully represent my problem. I was worried I'd leave out some detail that doesn't convey the underlying problem :S — narutoreplicate
– narutoreplicate, Commented Nov 1, 2012 at 13:45

Bryan Oakley · Accepted Answer · 2012-10-29 02:30:55Z

1

You need to bind the value of i at the time you create the widget:

staffButton = Button(..., command=lambda btn=i:self.openTabHere(isLeft,btn))

You probably need to do the same thing for isLeft, unless that's a static value.

answered Oct 29, 2012 at 2:30

Bryan Oakley

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2 Comments

narutoreplicate Over a year ago

IT WORKS!!!!!! My week of hell is over (sort of). staffButton = Button(..., command=lambda i=i : self.openTabHere(isLeft,i)) This does the trick. Followup Question: As you said, I'll need to do this with isLeft, but what would be the appropriate syntax?

Bryan Oakley Over a year ago

@narutoreplicate: The syntax would look something like lambda A=isLeft, B=i: self.openTabHere(A,B) Notice the pattern? Think of a lambda as a function without a name. The part after lambda and before the :is a list of arguments and their default values, as if you had done def some_func(A="abc", B="123").

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