Q:

Tkinter creating a widget without storing it in a some kind of container like a variable?

Good day. I was confused when creating a radiobutton or any kind of widget like the label widget inside a class method because it was not stored in a some kind of container like a variable. It's my first time seeing this kind of code: here it is
class Application(Frame):
    """ GUI Application for favorite movie type. """
    def __init__(self, master):
        """ Initiale Frame. """
        super(Application, self).__init__(master)
        self.grid()
        self.create_widgets()

    def create_widgets(self):
        """ Create widgets for movie type choices. """
        # Create description label
        Label(self,
              text = "Choose your favorite type of movie"
              ).grid(row=0, column=0, sticky= W)

        # create instruction label
        Label(self,
              text="Select one:"
              ).grid(row=1,column=0, sticky=W)

        Radiobutton(self,
                    text="Comedy",
                    variable=self.favorite,
                    value = "comedy.",
                    command = self.update_text
                    ).grid(row = 2, column = 0, sticky=W)

        # create Drama radio button
        Radiobutton(self,
                    text = "Drama",
                    variable = self.favorite,
                    value = "drama.",
                    command = self.update_text
                    ).grid(row = 3, column = 0, sticky = W)

        # create Romance button
        Radiobutton(self,
                    text = "Romance",
                    variable = self.favorite,
                    value = "romance.",
                    command = self.update_text
                    ).grid(row = 4, column = 0, sticky = W)

I usually see codes like this:
radio = Radiobutton(root)
radio.grid() 

Can you explain me what happen with the first code? How did it create a widget without storing it in a some kind of a variable like in a second code

A:

Tkinter is just a thin wrapper around an embedded Tcl interpreter which itself has the tk toolkit loaded. When you create a widget, the actual widget is represented as an object inside the tcl interpreter. 
Tkinter will create a python object that holds a reference to this tcl object, but the existence of the python object isn't required for the tcl/tk object to exist. If you create a widget without saving a reference, the widget is still created and still exists in the tcl/tk interpreter. 

