Project: Overview

Plan a mini app managing tasks with a stack and queue.

In this project we build an undo system for a text editor. Stack, queue and state printing will accumulate.

Step 1: prepare empty stack. Step 2: add action. Step 3: undo. Step 4: print state.

Each lesson includes the previous solution; the code grows step by step.

Stack logic

A stack works with LIFO (last-in first-out) logic: the last added is the first removed. Ideal for an undo system.

Each action is pushed onto the stack. When undoing it is popped. The most recent action is undone first.

In Python a list is used: append for push, pop for pop.

Write init_undo(). Return an empty list. Print [] with print(init_undo()).

Show example solution

def init_undo():
    # Empty undo stack
    return []
print(init_undo())

Next lesson: Undo stack