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Week 8: Decorators & Data Structures

Why Learn This?

This week deepens your Python fluency:

  • Decorators help you modify or extend function behavior — great for logging, security, and more.
  • Abstract Data Structures like stacks and queues teach you how to manage data efficiently.
  • You’ll also explore idiomatic Python, learning patterns pros use every day.

These topics build the bridge from intermediate to advanced Python, preparing you for technical interviews and large-scale systems.

Concepts & Notes

Decorators

A decorator is a function that takes another function and extends or modifies its behavior.

Basic Decorator

def my_decorator(func):
    def wrapper():
        print("Before the function")
        func()
        print("After the function")
    return wrapper

@my_decorator
def say_hello():
    print("Hello!")

say_hello()

Decorator with arguments

def repeat(func):
    def wrapper(*args, **kwargs):
        for _ in range(3):
            func(*args, **kwargs)
    return wrapper

@repeat
def greet(name):
    print(f"Hello, {name}!")

greet("Pythonista")

Abstract Data Structures

Stack (LIFO)

stack = []
stack.append(1)
stack.append(2)
print(stack.pop())  # 2

Queue (FIFO)

from collections import deque

queue = deque()
queue.append(1)
queue.append(2)
print(queue.popleft())  # 1

LinkedList (basic custom example)

class Node:
    def __init__(self, data):
        self.data = data
        self.next = None

n1 = Node(1)
n2 = Node(2)
n1.next = n2
print(n1.next.data)  # 2

Idiomatic Python

  • List Comprehensions
  • Using enumerate()
for i, value in enumerate(["a", "b", "c"]):
    print(i, value)
  • Dictionary Comprehensions
squares = {x: x**2 for x in range(5)}

Quiz – Week 8

  1. What is a decorator?

  2. What does LIFO stand for?

  3. Which Python module supports queue structures?

  4. What keyword is used to apply a decorator?

  5. True or False: enumerate() returns (index, value) pairs.

  6. What is the result of [x*2 for x in range(3)]?

Coding Challenges – Week 8

🔹 Challenge 1: Create a Basic Decorator

Instructions: Write a decorator that prints "Starting..." before and "Done." after the function call.

Learning Objective: Understand how decorators wrap and extend functions.

# TODO: Write a decorator that prints "Starting..." before and "Done." after the function call.

Challenge 2: Decorator with Arguments

Instructions: Write a decorator that logs the arguments a function is called with.

Learning Objective: Use *args and **kwargs in decorators.

# TODO: Write a decorator that logs the arguments a function is called with.

Challenge 3: Implement a Stack

Instructions: Use a list to simulate a stack. Push 3 elements, then pop and print each.

Learning Objective: Reinforce stack logic (LIFO).

# TODO: Use a list to simulate a stack. Push 3 elements, then pop and print each.

Challenge 4: Implement a Queue

Instructions: Use deque to implement a simple queue. Enqueue 3 values, then dequeue all.

Learning Objective: Reinforce queue logic (FIFO).

# TODO: Use `deque` to implement a simple queue. Enqueue 3 values, then dequeue all.

Challenge 5: Use enumerate() in a Loop

Instructions: Print the index and value of each item in a list using enumerate().

Learning Objective: Write clean, idiomatic loops.

# TODO: Print the index and value of each item in a list using `enumerate()`.

Challenge 6: Dictionary Comprehension

Instructions: Create a dictionary where keys are numbers 1-5 and values are their cubes.

Learning Objective: Learn dictionary comprehensions.

# TODO: Create a dictionary where keys are numbers 1-5 and values are their cubes.

Week 8 Summary

  • You wrote decorators to enhance or modify function behavior.
  • You practiced custom data structures like stacks, queues, and linked lists.
  • You used idiomatic Python constructs like enumerate() and comprehensions.
  • You’re now comfortable writing clean, expressive, and reusable code.

These patterns will empower your final capstone project and any advanced Python work.

For Next Week

Reading

Assignments

Complete the following exercises -- you can, of course, do them all:

  • 07_decorators
    • 07_01_quote_wrap.py
    • 07_03_text_decoration.py
    • 07_05_decorated_logging.py
  • 08_data_structures
    • 08_01_stack.py

Finally, start planning and working on a capstone project for the course. Your final project should demonstrate what you've learned:

  • A real-world Python app
  • Uses an external API
  • Stores data in a SQL database
  • Interacts via command-line or simple interface
  • Optional: include testing & decorators!

Additional resource

Data Structures & Algorithms course