StringVar

Author: crmpicco

gui-programming.md

@@ -79,4 +79,19 @@ for item in ["Laudrup", "McCoist", "Albertz", "Ferguson"]:
     # insert the item at the END of the listbox
     hof_gers.insert(tk.END, item)
 ```
-* `Canvas` - a widget that can be used to draw shapes, images, and text. Tkinter does not support 3D graphics. For complex 3D graphics, libraries such as [PyOpenGL](https://pyopengl.sourceforge.net/) and [Visualisation Toolkit (VTK)](https://pypi.org/project/vtk/) would be more suitable.
+* `Canvas` - a widget that can be used to draw shapes, images, and text. Tkinter does not support 3D graphics. For complex 3D graphics, libraries such as [PyOpenGL](https://pyopengl.sourceforge.net/) and [Visualisation Toolkit (VTK)](https://pypi.org/project/vtk/) would be more suitable.
+
+`StringVar` - a special variable that can be used to store a string value. It is used to store the value of a widget, such as an `Entry` or a `Label`. It can be used to get and set the value of a widget.
+
+:information_source: You need to associate a `StringVar` with a widget to make it work. For example, you can associate a `StringVar` with an `Entry` widget to get the value of the entry field, or at the very least the master widget (e.g. the `Tk()` root window)
+
+For example, this would throw an error because the `StringVar` is not associated with any widget:
+```python
+import tkinter as tk
+
+rrp = tk.StringVar()
+rrp.set("I have come here to chew bubble gum and kick ass, and I'm all out of bubble gum")
+
+window = tk.Tk()
+window.mainloop()
+```