How to Avoid Reassigning Button Commands in Tkinter For Loops Using Lambda Functions?

Assigning Button Commands in a Tkinter For Loop using Lambda

When creating buttons within a Tkinter for loop using lambda functions, it's crucial to avoid reassigning the same variable within the loop. This ensures that each button receives a unique parameter.

The Issue:

In the code provided:

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

The lambda function within the for loop references the same name variable, which gets reassigned during each iteration. As a result, all buttons invoke the same function with the last value assigned to name, leading to incorrect behavior.

The Solution:

To resolve this issue, you can bind the current value of the name variable to the lambda's keyword argument using default parameters:

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

By default keyword arguments, each button's lambda function has its own unique copy of the name variable, ensuring that the correct parameter is used when the button is clicked.

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