Functions and OOPS | Lecture 14 | Python Full Course For Beginners

Introduction

This tutorial provides a comprehensive overview of functions and Object-Oriented Programming (OOP) in Python, as discussed in the lecture. You'll learn about creating and using functions, understanding arguments, and exploring OOP concepts such as classes, objects, inheritance, and more. This guide is ideal for beginners looking to strengthen their Python programming skills.

Step 1: Understanding Functions

• Functions are reusable blocks of code that perform specific tasks.
• Define a function using the def keyword followed by the function name and parentheses.
• Example:

  def my_function():
      print("Hello, World!")
  

Step 2: Working with Arguments

• Functions can take input values known as arguments.
• Types of arguments:
  • Positional arguments: Values passed in the order defined.
  • Keyword arguments: Values passed using key-value pairs.
• Example:

  def greet(name):
      print(f"Hello, {name}!")
  
  greet("Alice")  # Positional argument
  greet(name="Bob")  # Keyword argument
  

Step 3: Using the Return Keyword

• The return statement is used to send a value back from a function.
• Example:

  def add(a, b):
      return a + b
  
  result = add(5, 3)
  print(result)  # Output: 8
  

Step 4: Implementing Placeholder Values

• You can use placeholders in function definitions to indicate where values should be passed.
• Example:

  def placeholder_function(value):
      pass  # Placeholder for future code
  

Step 5: Iteration in Functions

• Functions can perform operations iteratively using loops.
• Example:

  def print_numbers(n):
      for i in range(n):
          print(i)
  
  print_numbers(5)  # Output: 0, 1, 2, 3, 4
  

Step 6: Adding Docstrings

• Docstrings are used to document what a function does.
• Place a string at the beginning of the function definition.
• Example:

  def multiply(a, b):
      """Returns the product of a and b."""
      return a * b
  

Step 7: Handling Multiple Arguments

• Functions can accept multiple arguments.
• Example:

  def calculate_total(*args):
      return sum(args)
  
  total = calculate_total(10, 20, 30)
  print(total)  # Output: 60
  

Step 8: Key-Value Pairs as Arguments

• You can pass arguments as key-value pairs to functions.
• Example:

  def display_info(name, age):
      print(f"{name} is {age} years old.")
  
  display_info(age=25, name="John")  # Output: John is 25 years old.
  

Step 9: Exploring Lambda Functions

• Lambda functions are anonymous functions defined with the lambda keyword.
• They can take multiple arguments but have a single expression.
• Example:

  square = lambda x: x * x
  print(square(4))  # Output: 16
  

Step 10: Introduction to OOP Concepts

• Object-Oriented Programming focuses on using objects to represent data.
• Key concepts include:
  • Classes: Blueprints for creating objects.
  • Objects: Instances of classes.

Step 11: Implementing Classes

• Define a class using the class keyword.
• Example:

  class Dog:
      def bark(self):
          print("Woof!")
  
  my_dog = Dog()
  my_dog.bark()  # Output: Woof!
  

Step 12: Understanding the Self Reference

• The self keyword refers to the instance of the class itself.
• It is used to access variables and methods within the class.

Step 13: Utilizing the Init Method

• The __init__ method initializes the object's attributes when it is created.
• Example:

  class Car:
      def __init__(self, model):
          self.model = model
  
  my_car = Car("Toyota")
  print(my_car.model)  # Output: Toyota
  

Step 14: Exploring Inheritance

• Inheritance allows a class to inherit properties and methods from another class.
• Example:

  class Animal:
      def speak(self):
          print("Animal speaks")
  
  class Cat(Animal):
      def meow(self):
          print("Meow")
  
  my_cat = Cat()
  my_cat.speak()  # Output: Animal speaks
  my_cat.meow()    # Output: Meow
  

Step 15: Understanding Method Resolution Order (MRO)

• MRO defines the order in which base classes are searched when executing a method.
• Use ClassName.__mro__ to see the order.

Step 16: Learning About Polymorphism

• Polymorphism allows methods to do different things based on the object calling them.
• Example:

  class Bird:
      def fly(self):
          print("Flies")
  
  class Ostrich(Bird):
      def fly(self):
          print("Cannot fly")
  
  def make_it_fly(bird):
      bird.fly()
  
  make_it_fly(Bird())  # Flies
  make_it_fly(Ostrich())  # Cannot fly
  

Step 17: Working with Public and Private Methods

• Public methods can be accessed from outside the class, while private methods are restricted.
• Use an underscore _ to indicate a method is private.
• Example:

  class Example:
      def public_method(self):
          print("This is public")
  
      def _private_method(self):
          print("This is private")
  

Step 18: Understanding Abstraction

• Abstraction hides complex reality while exposing only the necessary parts.
• It can be implemented using abstract classes and interfaces in Python.

Conclusion

In this tutorial, we've covered essential concepts of functions and Object-Oriented Programming in Python. From defining functions and handling arguments to understanding classes and inheritance, these foundational topics are crucial for your development as a Python programmer. Continue practicing these concepts to solidify your understanding and explore more advanced topics in Python programming.