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Functions in Python

 

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Functions in Python

Functions in Python are reusable blocks of code that perform a specific task. They help in organizing code into manageable sections and avoid repetition. Functions are defined using the def keyword followed by the function name and parentheses ().

Defining a Function

A function is defined using the def keyword. Here's a simple example of a function that takes a parameter and prints a greeting message:


# Defining a function
def greet(name):
    # Function body
    print("Hello, " + name + "!")

# Calling the function
greet("Alice")  # Output: Hello, Alice!

Return Statement

The return statement is used to return a value from a function. If no return statement is used, the function returns None by default.


# Function with return statement
def add(a, b):
    return a + b

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

Default Arguments

Functions can have default argument values, which are used if no value is provided when the function is called.


# Function with default arguments
def greet(name, message = "Hello"):
    print(message + ", " + name + "!")

# Calling the function
greet("Alice")  # Output: Hello, Alice!
greet("Bob", "Good morning")  # Output: Good morning, Bob!

Variable-Length Arguments

Functions can accept a variable number of arguments using the *args and **kwargs syntax.


# Function with *args
def sum_all(*args):
    total = 0
    for num in args:
        total += num
    return total

# Calling the function
result = sum_all(1, 2, 3, 4)
print(result)  # Output: 10
    

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

# Calling the function
print_info(name="Alice", age=25, city="Wonderland")

Lambda Functions

Lambda functions are small anonymous functions defined using the lambda keyword. They are useful for short, throwaway functions.


# Lambda function
square = lambda x: x ** 2

# Using the lambda function
print(square(5))  # Output: 25
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