What is the main function of the stack data structure and in what scenarios is it used?

A stack is a data structure that operates on the Last In, First Out (LIFO) principle, meaning the last added element is the first to be removed. The main operations of a stack are adding an element (push) and removing an element (pop).

Stacks are widely used in the following scenarios:

• Managing function calls (call stack) in programming.
• Reverse traversal of data, for example, when traversing graphs or trees.
• Implementing undo actions in applications.
• Parsing expressions and calculating arithmetic expressions.

An example of a simple stack in Python using a list:

stack = []

# Adding an element
stack.append(1)
stack.append(2)

# Removing an element
top = stack.pop()  # top will be 2