Python Functions & Variable Scope | Nested Functions, Global & Local Variables Explained!

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📌 Python Programming Class 9 - Functions & Scope of Variables
Welcome to Class 9 of Python Programming! In this session, we continue our exploration of functions and dive deeper into variable scope and namespaces in Python.

📖 Key Topics Covered
✅ Defining Functions: Writing functions using def and following Python’s naming conventions.
✅ Nested Functions: How to write a function inside another function.
✅ Scope of Variables: Understanding local, global, and non-local variables.
✅ Namespaces in Python: Where variables live in memory and how their scope is determined.
✅ Accessing and Modifying Variables:
    🔹 Using global to modify global variables inside a function.
    🔹 Using nonlocal to modify variables in nested functions.
✅ Passing Functions as Arguments: How to send a function as a parameter to another function.
✅ Returning Values from Functions: How Python processes return statements.
✅ Positional & Keyword Arguments: Understanding *args and **kwargs for handling flexible function arguments.

📌 YouTube Video Summary (With Time Stamps) 📌
👋 Welcome to Python Programming - Class 9!
In this session, we explore functions in Python, focusing on their scope, execution flow, nested structures, and argument handling.

🕒 Time Stamps & Topics Covered
🔹 0:00 - Introduction
▶️ Overview of today's session: Functions, scope, and variables.

🔹 0:05 - Function Basics in Python
✔️ Defining a function (def function_name()).
✔️ Naming conventions & use of underscores (new_function).
✔️ Writing function body and parameters.

🔹 0:38 - Understanding Function Scope
🔹 What is variable scope?
🔹 Introduction to local & global variables.
🔹 Why some variables are not accessible outside their functions.

🔹 1:08 - Nested Functions & Indentation
🔹 What are nested functions?
🔹 Writing an inner function inside an outer function.
🔹 Understanding indentation rules in Python.

🔹 2:16 - Local vs Global Variables
✔️ Declaring global variables (a = 10).
✔️ Accessing global variables inside a function.
✔️ Why some variables are restricted within functions.
✔️ Example: Why D is accessible only within its function but A is accessible globally.

🔹 4:17 - Understanding Name Space in Python
🔹 What is namespace?
🔹 How Python assigns memory to variables.
🔹 Practical example: How Python stores variables in memory.

🔹 5:31 - Printing Variables & Execution Flow
✔️ Printing global variables inside functions.
✔️ What happens if we try to modify global variables within a function?
✔️ Understanding how Python tracks changes in variables.

🔹 6:41 - Can You Change Global Variables Inside Functions?
🔹 Example: Changing a inside a function – is it possible?
🔹 Why does Python raise an error when trying to modify a global variable inside a function?
🔹 Solution: Using the global keyword to modify global variables.

🔹 7:06 - Nested Functions & Scope of Variables
✔️ Understanding nested function execution.
✔️ Can we access variables from the outer function inside an inner function?
✔️ How control flows in nested functions.

🔹 8:07 - What is the Nonlocal Keyword?
🔹 How to modify variables inside a nested function.
🔹 Difference between global and nonlocal.
🔹 Example: Using nonlocal to modify a variable inside a nested function.

🔹 10:13 - Function Calls & Execution Order
✔️ Understanding how Python executes function calls.
✔️ Why inner functions cannot be accessed directly.
✔️ Example of calling nested functions correctly.

🔹 12:03 - Function Arguments & Parameters
🔹 Sending different types of data to functions:
🔸 Numbers
🔸 Strings
🔸 Lists
🔸 Other functions
🔹 How arguments are passed inside functions.

🔹 14:46 - Can You Pass a Function as an Argument?
🔹 Example: Passing a function inside another function.
🔹 How function calls execute in a nested manner.
🔹 Why returning values correctly is important.

🔹 16:31 - Returning Values from Functions
✔️ Understanding the return statement.
✔️ Why print() inside a function is not enough.
✔️ Using return values for further processing.

*🔹 18:52 - Understanding args and kwargs in Functions
🔹 What is *args? (Handling multiple positional arguments)
🔹 What is **kwargs? (Handling multiple keyword arguments)
🔹 Example: Sending multiple values to a function.
🔹 Why **kwargs returns a dictionary instead of a tuple.

🔹 22:42 - Conclusion & Next Steps
✔️ Key takeaways from today’s session.
✔️ Overview of Object-Oriented Programming (OOP) (coming up next!).
✔️ Transitioning into Data Science with Python.

🎯 By the End of This Video, You Will Learn:
✔️ How functions work in Python.
✔️ What local, global, and nonlocal variables are.
✔️ How nested functions impact variable scope.
✔️ How to pass lists, numbers, and even functions as parameters.
✔️ The role of *args and **kwargs in handling flexible arguments.

🚀 Stay tuned for the next class on Object-Oriented Programming! 🎉
💬 Comment below if you have any questions.