Functions in Python

Functions in Python are reusable blocks of code that perform a specific task. They help in organizing code, reducing redundancy, and improving readability.

1. Defining a Function

A function is defined using the def keyword.

def greet():
    print("Hello, World!")
 
# Calling the function
greet()

2. Function with Parameters

Functions can accept parameters to pass data.

def greet(name):
    print(f"Hello, {name}!")
 
# Calling the function
greet("Alice")

3. Function with Return Value

Functions can return values using the return statement.

def add(a, b):
    return a + b
 
# Calling the function
result = add(5, 3)
print("Sum:", result)

4. Default Parameters

Functions can have default values for parameters.

def greet(name="Guest"):
    print(f"Hello, {name}!")
 
# Calling the function
greet()  # Uses default value
greet("Bob")

5. Keyword Arguments

Keyword arguments allow specifying parameters by name.

def introduce(name, age):
    print(f"Name: {name}, Age: {age}")
 
# Calling the function with keyword arguments
introduce(age=25, name="Charlie")

6. Variable-Length Arguments

Functions can accept multiple arguments using *args and **kwargs.

Using *args for Positional Arguments

def add_numbers(*args):
    return sum(args)
 
print(add_numbers(1, 2, 3, 4, 5))  # Output: 15

Using **kwargs for Keyword Arguments

def display_info(**kwargs):
    for key, value in kwargs.items():
        print(f"{key}: {value}")
 
display_info(name="David", age=30, country="USA")

7. Lambda Functions

Lambda functions are anonymous functions that can have only one expression.

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

Conclusion

Functions help in making Python programs modular and efficient. Understanding functions enables better code organization and reuse.