Functions (In Depth)

🐍 Lesson 60: Python Functions (Defining & Calling Functions in Depth)

1. What is a Function?

In short → A function is a code block you group together so you can call the same task over and over.

In other words → A function is a reusable block of code that performs a specific task.

2. Why Use Functions?

Makes your code reusable
Keeps your code clean and modular
Makes maintenance easier

3. Summary

✅ Function = reusable code block

✅ Parameters → input values

✅ Return values → output results

✅ Default parameters, keyword arguments supported

python

# ===== 1. Basic Function =====
def greet():
    print("Hello, welcome to Python!")

greet()

# ===== 2. Function with Parameters =====
print(f"\n===== With Parameters =====")

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

greet("Sai")
greet("Aye")

# ===== 3. Function with Return Value =====
print(f"\n===== With Return =====")

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

result = add(5, 7)
print(f"Sum: {result}")

# ===== 4. Default Parameters =====
print(f"\n===== Default Parameters =====")

def greet(name="Guest"):
    print(f"Hello, {name}")

greet()        # Hello, Guest
greet("Aye")   # Hello, Aye

# ===== 5. Keyword Arguments =====
print(f"\n===== Keyword Arguments =====")

def introduce(name, age):
    print(f"My name is {name}, I am {age} years old.")

introduce(age=25, name="Sai")

# ===== 6. Multiple Return Values =====
print(f"\n===== Multiple Returns =====")

def calculate(a, b):
    return a + b, a * b, a - b

sum_val, product, diff = calculate(10, 5)
print(f"Sum: {sum_val}, Product: {product}, Diff: {diff}")

# ===== 7. Variable Arguments =====
print(f"\n===== Variable Arguments =====")

def sum_all(*args):
    return sum(args)

print(f"Sum: {sum_all(1, 2, 3, 4, 5)}")

# ===== 8. Keyword Arguments (kwargs) =====
print(f"\n===== Keyword Arguments =====")

def print_info(**kwargs):
    for key, value in kwargs.items():
        print(f"{key}: {value}")

print_info(name="Sai", age=25, city="Yangon")

You should see

Hello, welcome to Python! ===== With Parameters ===== Hello, Sai Hello, Aye ===== With Return ===== Sum: 12 ===== Default Parameters ===== Hello, Guest Hello, Aye ===== Keyword Arguments ===== My name is Sai, I am 25 years old. ===== Multiple Returns ===== Sum: 15, Product: 50, Diff: 5 ===== Variable Arguments ===== Sum: 15 ===== Keyword Arguments ===== name: Sai age: 25 city: Yangon