Python, Tkinter entry get to function (error was with function call from button)

Question

The entry value is just simply doesn't get passed into the function, whatever I do.

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

        name_var = tk.StringVar()

        name_entry = ttk.Entry(self, textvariable=name_var)
        name_entry.grid(row=1, column=1)

        button1 = ttk.Button(self, text="Registration", command=self.RegFunction(name_var.get()))
        button1.grid(row=4, column=4)

    def RegFunction(self, name)
        print(name)

Edit:
I just realized, if I add a variable to the function, it gets called as soon as I run the program, and it doesn't care about the button; but if I don't give it a variable, it works as it should, only when I push the button.

Here is the whole code

import tkinter as tk
from tkinter import ttk

class ToDoList(tk.Tk):

    def __init__(self, *args, **kwargs):

        tk.Tk.__init__(self, *args, **kwargs)


        container = tk.Frame(self)
        container.pack(side="top", fill="both", expand=True)

        container.grid_rowconfigure(0, weight=1)
        container.grid_columnconfigure(0, weight=1)

        self.frames = {}


        for F in (LogIn, Registration):
            frame = F(container, self)

            self.frames[F] = frame

            frame.grid(row=0, column=0, sticky="nsew")

        self.show_frame(LogIn)

    def show_frame(self, cont):
        frame = self.frames[cont]
        frame.tkraise()

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

        # label of frame Layout 2
        label = ttk.Label(self, text="Log In")

        label.grid(row=0, column=4, padx=10, pady=10)

        username_label = ttk.Label(self, text="Username :")
        username_label.grid(row=1, column=1)

        password_label = ttk.Label(self, text="Password:")
        password_label.grid(row=2, column=1)

        usrname_entry = ttk.Entry(self)
        usrname_entry.grid(row=1, column=2)

        password_entry = ttk.Entry(self)
        password_entry.grid(row=2, column=2)


        button2 = ttk.Button(self, text="Registration",
                             command=lambda: controller.show_frame(Registration))


        button2.grid(row=4, column=1, padx=10, pady=10)


class Registration(tk.Frame):
    def __init__(self, parent, controller):
        tk.Frame.__init__(self, parent)
        label = ttk.Label(self, text="Registration")
        label.grid(row=0, column=4, padx=10, pady=10)

        name_label = ttk.Label(self, text="Username:")
        name_label.grid(row=1, column=0)
        pass1_label = ttk.Label(self, text="Password:")
        pass1_label.grid(row=2, column=0)
        pass2_label = ttk.Label(self, text="Password again:")
        pass2_label.grid(row=3, column=0)

        name_var = tk.StringVar()
        name_entry = ttk.Entry(self, textvariable=name_var)
        name_entry.grid(row=1, column=1)

        pass1_entry = ttk.Entry(self)
        pass1_entry.grid(row=2, column=1)
        pass2_entry = ttk.Entry(self)
        pass2_entry.grid(row=3, column=1)
        k = 12

        button1 = ttk.Button(self, text="Registration", command=self.RegFunction(k))

        button1.grid(row=4, column=4, padx=10, pady=10)

        button2 = ttk.Button(self, text="Back to Login",
                             command=lambda: controller.show_frame(LogIn))

        button2.grid(row=4, column=0, padx=10, pady=10)

    def RegFunction(self, x):
        print("Something", x)


app = ToDoList()
app.mainloop()

You are passing the result of the function, rather than the function itself to ttk.Button — mousetail
– mousetail, Commented Jan 15, 2021 at 13:09
use self.name_var and in the regFunction use self.name_var.get() and change command=self.RegFunction(name_var.get()) to command=RegFunction — JacksonPro
– JacksonPro, Commented Jan 15, 2021 at 13:23

Nimantha · Accepted Answer · 2021-10-31 08:35:00Z

There's a difference between calling a function and passing in a function's name so it can be called later on. The ttk.Button command= expects a function name (or reference) to be passed in, so that the named or referenced function can be called later. You are calling the function rather than passing in its name, so things go awry.

Change:

    button1 = ttk.Button(self, text="Registration", command=self.RegFunction(name_var.get()))

to:

    button1 = ttk.Button(self, text="Registration", command=lambda: self.RegFunction(name_var.get()))

and you'll be closer to your goal. The lambda tells Python not to call the function but rather just return a reference to it that can be used to call it later.

Once you do that, you'll see that you have a typo in your function definition -- you're missing a colon at the end of the def statement. So, change:

def RegFunction(self, name)

to:

def RegFunction(self, name): # colon added at end

acw1668 · Accepted Answer · 2021-01-15 13:16:29Z

command=self.RegFunction(name_var.get()) will execute self.RegFunction() immediately. You need to use lambda:

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

        name_var = tk.StringVar()

        name_entry = ttk.Entry(self, textvariable=name_var)
        name_entry.grid(row=1, column=1)

        button1 = ttk.Button(self, text="Registration", command=lambda: self.RegFunction(name_var.get()))
        button1.grid(row=4, column=4)

    def RegFunction(self, name):
        print(name)

Note that your code did not call super().__init__(parent) inside __init__().

Y.Ynot · Accepted Answer · 2021-01-15 13:19:17Z

0

You are not calling the entry function, but the outcome of the function. Try it without the brackets:

button1 = ttk.Button(self, text="Registration", command=self.RegFunction(name_var))

Also, the RegFunction misses the colon:

def RegFunction(self, name):
        print(name)

edited Jan 15, 2021 at 13:19

answered Jan 15, 2021 at 13:10

Y.Ynot

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4 Comments

acw1668 Over a year ago

Did you test your proposal? It doesn't work.

Andreasz Over a year ago

still not working, but it also says in command line: <bound method StringVar.get of <tkinter.StringVar object at 0x7f52f302b6d8>>

JacksonPro Over a year ago

@Andreasz use @ acw1668 answer or just look into my comment.

Andreasz Over a year ago

sorry :D in the code, its there, i just forgot it here but it still doesnt work. I just realized, if I add a variable to the function, it gets called as soon as I run the program, and it doesn't care about the button; but if I don't give it a variable, it works as it should, only when I push the button. I'm clueless

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