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Functions in Python

📘 Python 👁 54 views 📅 Nov 05, 2025
⏱ Estimated reading time: 2 min

Functions in Python

Functions allow you to group code into reusable blocks that can be called multiple times.

1. Defining a Function

def greet():
    print("Hello, Python!")

  • def keyword is used to define a function.

  • Function name follows Python naming rules.

  • Parentheses () can contain parameters.

  • Colon : and indentation define the function body.

2. Calling a Function

greet()  # Output: Hello, Python!

3. Function with Parameters

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

greet_user("Alice")  # Output: Hello, Alice!

  • Parameters allow functions to accept input values.

4. Function with Return Value

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

result = add(5, 3)
print(result)  # Output: 8

  • return sends a value back to the caller.

5. Default Parameters

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

greet()        # Output: Hello, Guest!
greet("Alice") # Output: Hello, Alice!

  • Use default values if arguments are not provided.

6. Keyword Arguments

def describe_pet(name, animal="dog"):
    print(f"{name} is a {animal}")

describe_pet(animal="cat", name="Whiskers")  # Output: Whiskers is a cat

  • Pass arguments by name, not just position.

7. Variable-Length Arguments

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

print(add_numbers(1, 2, 3, 4))  # Output: 10

  • *args allows any number of positional arguments.

  • **kwargs allows any number of keyword arguments.

8. Key Points

  • Functions improve code reusability and readability.

  • Can accept parameters and return values.

  • Supports default, keyword, and variable-length arguments.

  • Always use meaningful function names for clarity.

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