问题销毁按钮 Tkinter，NameError

Question

I am relatively new to programming with Python, and was building a fairly simple Rock Paper Scissors game with Tkinter. Basically, I have a button, that calls this function, and in this function, I want to destroy the button that I had created, but a NameError arises.

Here is the relative code:

def choose(choice):
    if choice == "rock":
        Paper.destroy()
        Scissors.destroy()

def play():
    global Rock
    Rock = Button(root, image = rock_photo, padx = 30, pady = 10, bg = "#fcf003", command = lambda: choose("rock"))
    global Paper
    Paper = Button(root,image = paper_photo, padx = 30, pady = 10, bg = "#c603fc", command=lambda: choose("paper"))
    global Scissors
    Scissors = Button(root,image = scissor_photo, padx = 30, pady = 10, bg = "#39fc03", command=lambda: choose("scissors"))

    Rock.grid(row = 1, column = 0)
    Paper.grid(row = 1, column = 2)
    Scissors.grid(row = 1, column = 1)
play()

Furthermore, the Error:

NameError: name 'Paper' is not defined

Please let me know if I need to provide any more information. Also, I am using a 3.8 Interpreter and would like to not use classes just yet(I'm aware I'll have to start learning it soon).

Answer 1

global variables in a python function simply allow a function to read and modify a variable in the global scope. It does not create a variable. Assuming that your play() function is the first time that you define Rock , Paper , and Scissors , you must first create 3 variables outside of any function like this:

Rock = None
Paper = None
Scissors = None

Then in your choose() function, add the global variables, like this:

def choose(choice):
    global Rock
    global Paper
    global Scissors
    if choice == "rock":
        Paper.destroy()
        Scissors.destroy()

See Global and Local Variables in Python

Answer 2

You have to include the global keyword in every scope you want to use that global variable in. This works:

def choose(choice):
    global Paper
    global Scissors
    if choice == "rock":
        Paper.destroy()
        Scissors.destroy()

But generally, for things like these, I would pass the objects as parameters to the function instead, that is:

def choose(choice, paper, scissors):
    if choice == "rock":
        paper.destroy()
        scissors.destroy()