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Part 1: Programming & Python BasicsPart 2: Data Structures & FunctionsPart 3: Advanced Python & AI Foundation

Module 12: Functions

In this module, we will learn about Functions. A function is a block of reusable code designed to perform a specific task.

12.1 Why Functions?​

  • DRY (Don't Repeat Yourself): Instead of writing the same code in multiple places, you write it once inside a function and call it whenever needed.
  • Organized Code: Breaking down a large program into smaller functions makes it easier to read, understand, and debug.

12.2 Creating & Calling Functions​

In Python, we use the def keyword (short for "define") to create a function.

Syntax:​

def function_name():
    # code to execute

Example:​

# Creating a function
def greet():
    print("Welcome to Think IT Telugu!")

# Calling the function (running it)
greet() # Output: Welcome to Think IT Telugu!
greet() # Running it again

12.3 Parameters vs Arguments​

We can pass information into functions using variables:

  • Parameters: Variables listed inside the parentheses when defining the function.
  • Arguments: Actual values sent to the function when calling it.
# "name" is a Parameter
def greet_user(name):
    print(f"Hello {name}, welcome!")

# "Sai" and "Ram" are Arguments
greet_user("Sai")
greet_user("Ram")

12.4 The return Statement​

Instead of just printing a value, a function can send a value back to the main program using the return statement.

def add(a, b):
    return a + b

result = add(10, 20)
print("The sum is:", result) # Output: The sum is: 30

Note: A function stops executing immediately when it runs a return statement. Any code written below it will be skipped.

12.5 Default Parameters​

You can assign a default value to a parameter. If no argument is passed when calling the function, Python will use the default value.

def welcome(name, course="Python"):
    print(f"Hello {name}, welcome to the {course} course.")

welcome("Sai")            # Output: Hello Sai, welcome to the Python course.
welcome("Ram", "Java")    # Output: Hello Ram, welcome to the Java course.

12.6 Scope​

Scope refers to where a variable can be accessed in your code:

1. Local Scope:​

Variables created inside a function can only be used inside that function. They are not visible to the outside program.

def my_func():
    msg = "I am local"
    print(msg)

my_func()
# print(msg) # Throws an error! "msg" is not defined outside the function.

2. Global Scope:​

Variables created outside of all functions can be accessed anywhere in the program.

x = 100 # Global variable

def show():
    print("Inside function:", x) # Accessible inside the function

show()
print("Outside function:", x)

:::tip Best Practice Avoid modifying global variables inside functions. Keeping variables local to their functions makes your code cleaner and prevents bugs! :::

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