What are Functions in Python and How to Define Them?

In Python, a function is a block of organized, reusable code that performs a single action. Functions provide better modularity and code reusability.

Defining a Function

Use the def keyword to define a function:

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

Calling a Function

Invoke the function by using its name followed by parentheses:

message = greet("Alice")
print(message)  # Output: Hello, Alice!

Function Parameters

Functions can have parameters that act as input variables:

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

Default Parameters

You can assign default values to parameters:

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

*args and **kwargs

For variable-length arguments:

def func(*args, **kwargs):
    print(args)
    print(kwargs)

Anonymous Functions (Lambda)

Use lambda for small anonymous functions:

square = lambda x: x * x
print(square(5))  # Output: 25

Returning Values

Functions can return values using the return statement:

def multiply(a, b):
    return a * b
result = multiply(3, 4)

Scope of Variables

Variables defined inside a function are local to that function.

Conclusion

Functions are fundamental in Python programming, enabling code reuse and better organization. Mastering functions is essential for efficient coding.