如何访问 tkinter 类中 __init__() 方法中的元素？

Question

I'm trying to access an element from a list that is created in the following. The program switches between multiple pages, and I want receive input from the user to store as a string in another file.

class SignupPage(tk.Frame):
    def __init__(self, parent, controller):

        tk.Frame.__init__(self, parent, bg='light blue')

        ulabel = tk.Label(self, text="User Name").pack()
        uname = tk.StringVar()
        uEntry = tk.Entry(self, textvariable=uname). pack()

        plabel = tk.Label(self, text='Password').pack()
        psswd = tk.StringVar()
        pEntry = tk.Entry(self, textvariable=psswd).pack()

        def Signup():
            username = uname.get()
            password = psswd.get()

            credentials_list = [username, password]
            print(credentials_list)
            print(username, password)

            controller.show_frame(SignupPage2)

        nextbutton = tk.Button(self, text='Next', command=Signup).pack()
        backbutton = tk.Button(
            self, text='Back', command=lambda: controller.show_frame(WelcomePage)).pack()

I want to access the username variable in another file, so I imported the class SignupPage.

from app import SignupPage

However, trying to access the element by typing the following doesn't work.

print(SignupPage.__init__.Signup.credentials_list[0])

How can I access the username variable?

Answer 1

Let's start with the following function inside your SignupPage class`:

def Signup():
    username = uname.get()
    password = psswd.get()

    ...

You want to access username inside that function. Unfortunately, username only exists inside Signup() , and cannot be accessed by using the dot operator. The same goes for the rest of the variables inside the function. So, you cannot get the username value by using

SignupPage.__init__.Signup.credentials_list[0]

We have to do something else. One thing we could do is put Signup() outside of __init__() and give SignupPage some instance variables. The SignupPage class would look something like the following.

class SignupPage(tk.Frame):
    def __init__(self, parent, controller):
        tk.Frame.__init__(self, parent, bg='light blue')

        self.credentials_list = list()

        ulabel = tk.Label(self, text="User Name").pack()
        self.uname = tk.StringVar()
        uEntry = tk.Entry(self, textvariable=self.uname). pack()

        plabel = tk.Label(self, text='Password').pack()
        self.psswd = tk.StringVar()
        pEntry = tk.Entry(self, textvariable=self.psswd).pack()

        nextbutton = tk.Button(self, text='Next', command=self.Signup).pack()
        backbutton = tk.Button(self, text='Back', command=lambda: controller.show_frame(WelcomePage)).pack()
        self.pack()

    def Signup(self):
        username = self.uname.get()
        password = self.psswd.get()

        self.credentials_list = [username, password]
        print(self.credentials_list)
        print(username, password)

        controller.show_frame(SignupPage2)

With this one, when we press the "Next" button, an instance of the SignupPage class will hold the values entered in the username and password text fields. To create an instance of the class, we simply do:

# root = tk.Tk()
signupPage = SignupPage(root, controller)

At this point, we can now access credentials_list by doing:

signupPage.credentials_list

Remember to pass the same instance of SignupPage to anything that will get the value of any attributes the class has.

I reckon that what I suggested is not the best design, but it should at least give you an idea on how to solve your problem.

---

Side Note : One way you can improve upon this is to use to provide a getter method for SignupPage that returns the value of credentials_list , instead of having to access the aforementioned variable by doing <instance>.credentials_list . Doing this is generally a better programming practice than the other method.