Tkinter assign button command in loop with lambda

Question

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

def a(self, name):     print(name)  users = {"Test": "127.0.0.0", "Test2": "128.0.0.0"} row = 1 for name in users:     user_button = Tkinter.Button(self.root, text=name,                                  command=lambda: self.a(name))     user_button.grid(row=row, column=0)     row += 1 

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?

Answer 1

The problem is your lambda expression in the for loop. It is using the name variable, but the name variable gets reassigned each iteration of 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 lambda expression like so:

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

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