Show MessageBox if Entry empty

Question

Could someone tell me what`s wrong I did?! I am tring to create GUI with tkinter in Python 3. If user click the button and in the same time Entry is empty I want to show messageBox. Here below my code that I used.

Right know I have this ERROR:

if len(self.entryBox.get()) == 0:
AttributeError: 'NoneType' object has no attribute 'get'

Also I tried to use this if self.entryBox is None: but in that case I see messageBox immediately after run the project which is now correct. I am really comfused.

CODE:

    from tkinter import *

    class Application(Frame):
         def __init__(self, master):
            super(Application, self).__init__(master)
            self.grid()
            self.widgets()

         def widgets(self):
            self.entryBox = Entry(self).grid()
            Button(self, text="Submit", command=self.search()).grid()

         def search(self):
             if len(self.entryBox.get()) == 0:
                 tkinter.messagebox.showinfo("Warning!", "Box is empty! Write something")
             else:
                 do_something()

    # main
    root = Tk()
    root.title("Title")
    app = Application(root)
    root.mainloop()

Answer 1

1. The line self.entryBox = Entry(self).grid() will assign the result of .grid() to self.entryBox. Intead, try this:

   self.entryBox = Entry(self)
   self.entryBox.grid()
   

2. By doing Button(self, text="Submit", command=self.search()).grid() you have a similar problem, as you run the search method once and then bind the result of that method to the command parameter. Instead, this should work (note the absence of ():

   Button(self, text="Submit", command=self.search).grid()