Trying to create a login page using tkinter in python, doesn't seem to work

Question

The below code is what i am working on, I am trying to create a login page and validate username and password. Ideally loginValidate function should be invoked when i click on the submit button, but it is invoked even before i do so. Also the user_login and pwd_login values doesn't seems to be passed to the function loginvalidate. Kindly help me in resolving the issue.

import tkinter as tk
import tkinter.messagebox as tm
from tkinter import *
import sys

FONTT = ("Times", "12", "bold italic")

class myApp(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 = {}

        frame = LoginPage(container,self)
        self.frames[LoginPage] = frame
        frame.grid(row = 0,column = 0,sticky = "nsew")

        self.show_frame(LoginPage)

    def show_frame(self,cont):

        frame = self.frames[cont]
        frame.tkraise()    

def loginValidate(user,pwd):
    if(user == "yogesh" and pwd == "123456"):
        print("1")
    else:
        print("2")
        tm.showerror("Login error", "Incorrect username or password")

class LoginPage(tk.Frame):

    def __init__(self,parent,controller):
        tk.Frame.__init__(self,parent)
        usr_login = StringVar()
        pwd_login = StringVar()
        userLabel = tk.Label(self,text = "Name",font = FONTT )
        passwordLabel = tk.Label(self,text = "Password", font = FONTT)

        userEntry = tk.Entry(self, textvariable = usr_login, bd=5)
        passwordEntry = tk.Entry(self, textvariable=pwd_login,bd=5,show = "*")

        submitButton = tk.Button(self,text = "Login",command = lambda: loginValidate(usr_login.get(),pwd_login.get()))
        quitButton = tk.Button(self,text = "Quit",command =lambda: app.destroy)

        userLabel.grid(row = 0,sticky = "E",padx =10,pady =10)
        passwordLabel.grid(row =1,sticky = "E",padx =10,pady =10)
        userEntry.grid(row=0,column=1,padx =10,pady =10)
        passwordEntry.grid(row=1,column=1,padx =10,pady =10)
        submitButton.grid(row =2,column =1,padx =10,pady =10)
        quitButton.grid(row=2,column=2,padx =10,pady =10)

app = myApp()
app.mainloop()

Answer 1

Look at what you've passed for the command:

loginValidate(usr_login.get(),pwd_login.get())

You're calling the function and passing what this function returns as the command.

Simple fix = use lambda

lambda: loginValidate(usr_login.get(), pwd_login.get())