What are Python modules?

Modules are essential building blocks in Python, especially when handling large projects. Simply put, modules are Python files that can be imported and utilized across different programs as reusable pieces of code. They help organize code logically and make it more maintainable. By breaking large codebases into smaller, manageable, and reusable components, modules enhance code readability and reduce redundancy.

How to make a Python module

As mentioned earlier, a Python module is simply a file containing Python code. The file name is the module name with the suffix .py added. Modules can contain functions, classes, variables, and runnable code. This code can be imported and used in other files and enables us to organize our code logically.

Here’s a sample code that we can save in a .py file and create a Python module.

What can we include in a module?

There is a limitation as to what we can include in a module and what we cannot.

We can include:

• Functions

• Classes

• Variables

• Executable code (although it’s generally recommended to limit this to improve reusability)

We cannot include:

• Code that has to be executed as part of another environment or language

• Direct dependencies on hardware or specific OS-level features unless the module is specifically designed for them

Where should we save the module?

After writing the code for a custom module, it’s important to save it in a location accessible to the Python interpreter. By default, Python looks for modules in:

• The directory of the script being run

• The PYTHONPATH environment variable (if set)

• The standard library directories

So, we can save the module in the same directory as the script that will import it, or we can place it in one of the directories specified in sys.path. To see a sample list of directories included in the Python path, run the code below.

How to import and use a Python module

To import a module, we use the import statement. Once imported, we can use the module’s functions, classes, and variables.

Syntax

To import a module, we simply write the import statement followed by the module name.

We can also import specific components using the from keyword:

Example

We have saved the module we created earlier as mymodule.py in the /usercode directory that was a part of the list of Python paths we obtained. In this code, let’s import that module and use its code.

Built-in Python modules

Each version of Python comes with a rich standard library, a collection of modules that provide standardized solutions for many problems that Python programmers face. Some popular built-in modules include:

• math: This provides access to mathematical functions

• datetime: This supplies classes for manipulating dates and times

• os: This provides a way of using operating system-dependent functionality

• sys: This provides access to system-specific parameters and functions

• random: This implements pseudo-random number generators

These modules can vary depending on the version of Python you have installed. For a complete list of built-in modules specific to your version of Python, refer to the Python Module Index.

Example

Using the math module to calculate the square root of a number:

Mastering modules is a key step in becoming a proficient Python developer. By learning how to create, import, and manage modules, you can write cleaner, more maintainable code and take full advantage of Python’s rich ecosystem.