4. Add Radio Buttons for Pizza Types

• Objective: Add radio buttons for selecting pizza types.

• Content:

  • Introduction to radio buttons.

  • Creating and positioning radio buttons for Pizza Type.

  • Using StringVar to manage radio button values.

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4.1. Introduction to Radio Buttons

• Radio buttons allow users to select one option from a set of mutually exclusive options.

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4.2. Creating and Positioning Radio Buttons for Pizza Type

Place the following code below the other widget code in Section "4. TKINTER WIDGETS"

This code creates a label and a set of radio buttons for selecting a pizza type.

The selected pizza type is stored in a StringVar named pizza_var, which is initialized to "Margherita".

The radio buttons are placed vertically inside a frame and aligned to the left.

# Pizza Type (Radio buttons)
pizza_label = tk.Label(root, text="Pizza Type:")
pizza_label.grid(row=1, column=0, padx=10, pady=5, sticky="ne")

pizza_var = tk.StringVar(root)
pizza_var.set("Margherita")

pizza_frame = tk.Frame(root)
pizza_frame.grid(row=1, column=1, padx=10, pady=5, sticky="w")

for pizza in ["Margherita", "Pepperoni", "Hawaiian", "Veggie"]:
    radio_button = tk.Radiobutton(pizza_frame, text=pizza, variable=pizza_var, value=pizza)
    radio_button.pack(anchor="w")

1. Label Creation:

   pizza_label = tk.Label(root, text="Pizza Type:")
   pizza_label.grid(row=1, column=0, padx=10, pady=5, sticky="ne")
   

   • This line creates a label widget with the text "Pizza Type:".

   • The grid method places the label in the second row (row=1), first column (column=0) of the grid layout.

   • padx and pady add padding around the label for better spacing.

   • sticky="ne" aligns the label to the northeast (top-right) of its grid cell.

2. StringVar Initialization:

   pizza_var = tk.StringVar(root)
   pizza_var.set("Margherita")
   

   • pizza_var is a StringVar object that holds the value of the selected pizza type.

   • pizza_var.set("Margherita") sets the default value to "Margherita".

   • This means that when the GUI is first displayed, "Margherita" will be the pre-selected option.

Tkinter variables (StringVar, IntVar, etc.) aren't normal Python strings; they are special objects linked to Tkinter's internal engine.

By passing root, tk.StringVar(root), you are saying, "This variable belongs to this specific window."

If that window is ever closed or destroyed, the memory used by that variable is safely cleaned up along with it.

3. Frame Creation:

   pizza_frame = tk.Frame(root)
   pizza_frame.grid(row=1, column=1, padx=10, pady=5, sticky="w")
   

   • This creates a frame widget to contain the radio buttons.

   • The grid method places the frame in the second row (row=1), second column (column=1) of the grid layout.

   • sticky="w" aligns the frame to the west (left side) of its grid cell.

4. Radio Buttons Creation:

   for pizza in ["Margherita", "Pepperoni", "Hawaiian", "Veggie"]:
       radio_button = tk.Radiobutton(pizza_frame, text=pizza, variable=pizza_var, value=pizza)
       radio_button.pack(anchor="w")
   

   • This loop creates a radio button for each pizza type in the list.

   • Each Radiobutton is placed inside pizza_frame.

   • text=pizza sets the label of the radio button.

   • variable=pizza_var links the radio button to the pizza_var variable.

   • value=pizza sets the value of pizza_var when the radio button is selected.

   • pack(anchor="w") arranges the radio buttons vertically, aligned to the left.