Modules and Packages in Python

In Python, modules and packages are fundamental components for organizing and reusing code. They help you to structure your code into manageable and logical units. This section covers the basics of creating and using modules and packages in Python.

10.1 Modules

A module is a file containing Python definitions and statements. The file name is the module name with the suffix .py appended. Modules help in organizing code logically and allow you to reuse code across different programs.

10.1.1 Creating a Module

To create a module, you simply create a Python file with some functions or variables. For example, create a file named math_functions.py with the following content:

# math_functions.py

def add(x, y):
    return x + y

def subtract(x, y):
    return x - y

10.1.2 Using a Module

Once you have created a module, you can use it in other Python files using the import statement. For example:

# main.py

import math_functions

result_add = math_functions.add(5, 3)
result_subtract = math_functions.subtract(5, 3)

print("Addition:", result_add)
print("Subtraction:", result_subtract)

This code imports the math_functions module and uses its functions to perform addition and subtraction.

10.2 Packages

A package is a way of organizing related modules into a directory hierarchy. A package is a directory that contains a special file named __init__.py and other module files. The __init__.py file is executed when the package is imported and can be used to initialize the package or set up the namespace.

10.2.1 Creating a Package

To create a package, follow these steps:

1. Create a directory for your package.
2. Add an __init__.py file inside the directory.
3. Add module files to the directory.

For example, create a directory named my_package with the following structure:

my_package/
    __init__.py
    module1.py
    module2.py

Here is an example content for module1.py:

# module1.py

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

10.2.2 Using a Package

To use a package, import the modules from the package. For example:

# main.py

from my_package import module1

message = module1.greet("Alice")
print(message)

This code imports the module1 from the my_package package and uses its greet function.

10.3 Standard Library and Third-Party Packages

The Python Standard Library is a collection of modules and packages that come with Python and provide a wide range of functionality. Examples include math, datetime, and os.

Third-party packages are additional packages that you can install using package managers like pip. Examples include requests, numpy, and pandas.

10.3.1 Installing Third-Party Packages

To install a third-party package, use the pip command. For example:

pip install requests

This command installs the requests package, which allows you to send HTTP requests easily.