The line of code `output_label.config(text="Invalid input.")` is used in a...

The line of code output_label.config(text="Invalid input.") is used in a graphical user interface (GUI) application, generally created using the Tkinter library in Python.

Here’s what this specific line does:

• output_label is an instance of a Tkinter Label widget that displays text on the GUI.
• The .config() method is used to modify the properties (or configuration options) of the widget, in this case, the text property.
• text="Invalid input." updates the text displayed by the output_label widget to "Invalid input."

In plain terms:

This code updates the text of the output_label label to display the message "Invalid input." on the GUI. It is likely triggered when some part of the program detects an input error.