Python Decorators Lecture Notes

Introduction

• Speaker: Devin Wendy
• Topic: Decorators in Python

Functions Recap

• Purpose: Perform specific tasks
• Example: Division function
  • Function: def division(a, b): return a / b
  • Usage: print(division(4, 2)) outputs 2.0
  • Expected Result: print(division(2, 4)) outputs 0.5

Problem Statement

• Requirement: Ensure numerator is always greater than or equal to denominator
• Solution Proposal: Automatically swap values if numerator < denominator

Initial Code Modification

• Logic: Swap logic
  • Before modification: def division(a, b): return a / b
  • After modification: def division(a, b): if a < b: a, b = b, a return a / b
  • Output: division(2, 4) returns 2.0

Problem with Direct Modification

• Scenario: Existing function in another file
  • No access to modify original function code

Introducing Decorators

• Purpose: Add functionality to existing function without modifying it
• Definition: A decorator is a function that takes another function and extends its behavior

Creating a Decorator

• Decorator Function: def smart_div(func): def inner(a, b): if a < b: a, b = b, a return func(a, b) return inner
• Usage: @smart_div def division(a, b): return a / b
  • Call: print(division(2, 4)) should output 2.0

Key Points

• Function as Parameter: Decorators take a function as an argument
• Function Inside Function: Can define a function within another function
• Returning Functions: The decorator returns the inner, modified function
• Assigning New Function:
  • Example: division = smart_div(division)

Benefits of Decorators

• Modifies behavior without altering original function
• Compilation Time Changes: Behavior is modified at compile-time

Summary

• Decorators: Enhance or modify functionality of functions
• Use Cases: Useful when original function cannot be modified or should remain unchanged
• Python Decorators: Demonstrates Python's ability to handle function-based programming paradigms

Conclusion

• Feedback: Encouraged to ask questions and subscribe for more content