如何修复 tkinter 按钮命令调用自身不起作用的错误？

Question

I want to have a button that has a command which quit/destroys a few other objects, including itself:

example:

B1 = Button(root, command= delete) # contains other settings too
def delete():
    B1.destroy()
    # contains destruction of other objects too

example code of it in the script(incomplete):

def mainpage():
    signup_btn = Button(root,text="Sign-Up", width=10, height=3, font=("courier", 16, "bold"), command=signup_page())
    signup_btn.place(relx=0.5 , rely=0.4, anchor=(CENTER))
    login_btn = Button(root,text = "Log-In", width=10, height=3, font=("courier", 16, "bold"), command=login_page())
    login_btn.place(relx=0.5 , rely=0.6, anchor=(CENTER)) 


    def signup_page():
        # destroy previous page
        signup_btn.destroy()
        login_btn.destroy()

        # setup new page
        title = Label(root, text="Enter your username and password, then press save and proceed to the log-in page!", height= 4, width=30, font=("courier", 16, "bold"))
        title.place(relx=0.5, rely=0.2, anchor=TOP)





    def login_page():
        signup_btn.destroy()
        login_btn.destroy()

in this case, the login_btn contains a function, calling to destroy itself and another button. this causes an error because if I place the UDF above the button's initialisation, the UDF has an error because the button being called inside is not initialised and vice versa if I put the button above the UDF

this causes an error in which when the button is initialised, the command does not exist. and if i initiate the command first, the button does not exist. its not just this specific scenario, it happen many times throughout the script where i an trying to call a variable/udf that is not yet created but its the same the other way round.

for some reason,e it works in 1 part of the script but the same logic works nowhere else. so i think im missing something about the part that works

i tried classes, different structures, or editing the button afterwards but it doesn't work.

Answer 1

Try changing command=signup_page() to command=lambda: signup_page() and command=login_page() to command=lambda: login_page()

You could also write your program using classes, it should look somewhat like this:

from tkinter import *


class App(Tk):
    def __init__(self):
        super().__init__()

        self.geometry("720x480")
        self.title('Test')

        self.signup_btn = Button(self, text="Sign-Up", width=10, height=3,
                                 font=("courier", 16, "bold"), command=self.signup_page)
        self.signup_btn.place(relx=0.5, rely=0.4, anchor=(CENTER))

        self.login_btn = Button(self, text="Log-In", width=10, height=3,
                                font=("courier", 16, "bold"), command=self.login_page)
        self.login_btn.place(relx=0.5, rely=0.6, anchor=(CENTER))

    def signup_page(self):
        # destroy previous page
        self.signup_btn.destroy()
        self.login_btn.destroy()

        # setup new page
        title = Label(self, text="Enter your username and password, then press save and proceed to the log-in page!",
                      height=4, width=30, font=("courier", 16, "bold"))
        title.place(relx=0.5, rely=0.2, anchor=(N))

    def login_page(self):
        self.signup_btn.destroy()
        self.login_btn.destroy()


if __name__ == "__main__":
    app = App()
    app.mainloop()