[Tkinter] Make my button text update?

[deanhystad]

The easiest way to do this is make bankValue a StringVar or IntVar. In this example I make it a StringVar so I can format it to have two decimal places.

import tkinter as tk

def addToBank(amount):
    balance = float(bankValue.get()) + amount
    bankValue .set(f'{balance:.2f}')

gameWindow = tk.Tk()
bankValue = tk.StringVar()
bankValue.set('0.00')
button1 = tk.Button(gameWindow, command=lambda:addToBank(1.25), textvariable=bankValue)
button1.pack()

gameWindow.mainloop()

This code sets your callback function to None.

command=addToBank(1)

command is None because addToBank(1) calls the function and uses the return value (None) and the value for command. You probably wanted this:

command=addToBank

But this does not provide an argument for "amount" in addToBank(). You could get around this by providing a default value for amount.

def addToBank(amount=1.25):
    balance = float(bankValue.get()) + amount
    bankValue .set(f'{balance:.2f}')

You can also use a lambda expression to bind an argument to the function. The same kind of thing can be done using functools.partial