Why is my Tk button being pressed automatically?

Question

In the code below, clicking the button should change the black text from Hello to Goodbye. But when I run the program, it immediately says Goodbye.

Answer 1

For future reference:

If you want to send parameters to the function, simply add lambda:

Example for a button with the command callback():

yourButton = Tkinter.Button(root, text="Go!", command= lambda: callback(variableOne, variableTwo, variableThree)).pack()