Tkinter mainloop broken, messagebox keeps popping up [duplicate]

Question

class StartUp():
    def __init__(self):
        pass

    def verify(self):
        username = ("s")
        password = ("s")
        
        usernameEntry = usernameVar.get()
        passwordEntry = passVar.get()

        start = StartUp()

        if usernameEntry == username and passwordEntry == password:
            start.login() 
        else: 
            #messagebox.showerror("Error","Wrong Credentials")

            
    def login(self):
        #Create a window
        global usernameVar, passVar
        
        verify = StartUp()
        
        window = Tk()
        window.title("Login")
            
        userPassLabel = Label(window, font="Helvetica 18 bold", text="Royal Mail")
        userPassLabel.grid(row=0, column=0, sticky=W)

        usernameVar = StringVar()
        usernameLabel = Label(window, font="Arial", text="Username:")
        usernameLabel.grid(row=1, column=0, sticky=W)
        usernameEntry= Entry(window, width=30, bg="light blue",textvariable = usernameVar, )
        usernameEntry.grid(row=1, column=1, sticky=W)
            
        passVar = StringVar()
        passLabel = Label(window, font="Arial", text="Password:")
        passLabel.grid(row=2, column=0, sticky=W)
        passEntry= Entry(window, width=30, bg="light blue",textvariable = passVar, show ="●")
        passEntry.grid(row=2, column=1, sticky=W)
        
        b1= Button(window, text="Enter", command=verify.verify())
        b1.grid(row=3, column=0, sticky=W)

        window.mainloop()


start = StartUp()
start.login()

The code seems to not work. The message box will just pop up. The enter button then doesn't work. Not sure what is wrong. I'm very new to OOP so not sure whether it's to do with that.

An additional question is how am I able to carry one variable from an input box in one window/class to another window/class? Is global a viable option or is there a better way I can use .get() from an Entry box.

Thanks for the help

Delrius Euphoria · Accepted Answer · 2021-04-04 15:09:52Z

2

When you use (), you are calling the function immediately. And when you use () with a button, it destroys the purpose of having a button itself. So remove the parenthesis, ().

b1 = Button(window, text="Enter", command=verify.verify)

When the function gets called, the value inside the entry are empty and hence else is triggered.

answered Apr 4, 2021 at 15:09

Delrius Euphoria

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8 Comments

sebtheoo Over a year ago

This fixed it, thanks :)

martineau Over a year ago

@CoolCloud: Re-answering duplicate questions is not the best way to boost your rep…

sebtheoo Over a year ago

@CoolCloud yeah, you answered so quick I had to wait 5 mins :)

TheLizzard Over a year ago

@martineau Most of the time it's easier to just answer the question. I think that that is a flaw with stackoverflow. The only solution that I can think of is a website with the most common tkinter mistakes that I can just bookmark.

Delrius Euphoria Over a year ago

@martineau Laziness? I mean we all have our own job apart from answering questions and looking for duplicates too right? I did have all this copied somewhere, but I lost all of it on a system reset too. We could just ignore this question and wait for someone else to mark as duplicate too though. But I don't think ignoring and hoping is the best practice.

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