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Tkinter assign button command in loop with lambda

I'm trying to create a few buttons (with a for) like so:

def a(self, name):
    print name

users = {"Test":"", "Test2":""}
row = 1
for name in users:
    user_button = Tkinter.Button(self.root,
                                 command=lambda: self.a(name))
    user_button.grid(row = row, column = 0)

and for the buttons to each get their own parameter (Test getting Test and Test2 getting Test2) but when i press the buttons they both print "Test2" which means they are using the same function with the same parameter.

How can I solve this?

The problem is your lamba in the for loop. Your lambda is using the name variable, but the name variable gets reassigned each time through the for loop. So in the end, all of the buttons get the last value that name was assigned to in the for loop. To avoid this you can use default keyword parameters in your lamba expression like so:

user_button = Tkinter.Button(self.root,
                             command=lambda name=name: self.a(name))

This binds the current value of the name variable to the lamba's name keyword argument each time through the loop, producing the desired effect.

  • 43
Reply Report
    • It is not a tkinter issue, it is an issue concerning nesting of functions, closures, etc. It as well exists in completely other contexts. Nevertheless +1, as it otherwise describes exactly what happens.

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