Functions in Programming

Functions

• A function is a group of statements within a program designed to perform a specific task.
• It's more efficient to break down large programs into smaller, manageable functions.
• This approach, known as the "divide and conquer" method, makes code more readable and easier to maintain.
• Modularized programs structure each task as a separate function.

Benefits of Modularizing Programs

• Simple Code: Small functions are easier to understand than long, complex code blocks.
• Code Reusability: Define a function once and use it repeatedly.
• Improved Testing: Each function can be tested independently.
• Faster Development: Functions can be developed for common tasks and re-used in other parts of the program.
• Teamwork Facilitation: Different programmers can work on separate functions concurrently.

Void Functions and Value-Returning Functions

• Void Functions: Perform certain actions, but do not return a value back to the calling part of the program.
• Value-Returning Functions: Perform actions and return a value to the calling part of the program.

Function Names

• Function names follow the same rules as variable names (e.g., no spaces, start with a letter or underscore).
• Use descriptive verbs emphasizing the function’s action.
• Examples: calculate_area, display_message, get_input.
• Capitalization and lowercase letters are considered distinct.

Function Definitions (Python)

• General format:

def function_name():
    statement
    statement

Local Variables

• Created inside a function and cannot be accessed outside the function.
• A local variable’s scope is the function in which it's created.
• Can only be used after it's created; using a local variable before its creation will generate an error.

Passing Arguments

• Arguments are data values passed into a function when it's called.
• Parameters are variables that accept arguments within a function.
• Python allows you to pass multiple arguments (data), and specify which parameter the argument should be assigned to, if necessary.

Global Variables

• A variable accessible to all functions within a program file.
• Modifying a global variable inside a function will only affect that variable's value locally.
• Modifying a global variable within a function can be achieved by using the 'global' keyword

Value-Returning Functions

• A function that returns a value back to the program.
• Python provides pre-built functions, which need to be imported (e.g., using the import keyword) to be used.

Returning Multiple Values

• Functions can return multiple values separated by commas.

Modules

• A module is a Python file containing code.
• It helps make large programs more manageable through modularization (splitting into smaller modules).
• Filenames should typically end with .py.
• Cannot be a Python reserved word (e.g., for).
• Modules are imported using the import keyword.

Docstrings

• Docstrings provide clear descriptions of a function's purpose and how it works.
• They aid in documentation and understanding code.
• Docstrings are enclosed in triple quotes ("""Docstring here""") and placed at the beginning of a function, module, or class.
• They are used to generate documentation and explain what the code is designed to do.