Structuring a Python Application

When developing a non-trivial end-user desktop application in Python, it’s essential to have a well-organized project structure. A good structure makes maintenance easier, is friendly to Integrated Development Environments (IDEs), and facilitates source control branching and merging, as well as the generation of install packages.

Project Structure Overview

A typical Python project should include several key directories and files:

• Top-level directory: This is the root directory of your project. It’s a good practice to name it after your project.
• bin/ or scripts/ directory: This directory contains executable scripts that serve as entry points for your application.
• Package directory: This directory holds the actual Python package and should be named after your project. Inside this directory, you can have subdirectories for different modules or components of your application.
• tests/ directory: This directory contains unit tests and acceptance tests for your application. It’s common to place it inside the package directory or as a separate top-level directory.
• docs/ directory: This directory stores project documentation, such as user manuals, API documentation, and installation guides.
• setup.py file: This file contains setup instructions for your project, including metadata like the project name, version, and dependencies.

Detailed Project Structure

Here’s a more detailed example of a Python project structure:

myproject/
|-- bin/
|   |-- myproject
|
|-- myproject/
|   |-- __init__.py
|   |-- main.py
|   |-- utils/
|   |   |-- __init__.py
|   |   |-- helper.py
|   |
|   |-- tests/
|       |-- __init__.py
|       |-- test_main.py
|
|-- docs/
|   |-- conf.py
|   |-- generated
|   |-- index.rst
|   |-- installation.rst
|   |-- modules.rst
|   |-- quickstart.rst
|   |-- myproject.rst
|
|-- requirements.txt
|-- setup.py
|-- README.md
|-- LICENSE

Best Practices

When structuring your Python project, keep the following best practices in mind:

• Avoid using a src/ or lib/ directory as the top-level package directory. Instead, use the project name directly.
• Keep tests inside the package directory to make it easier to run them against an installed version of the application.
• Use a consistent naming convention for your directories and files.
• Keep the top-level directory clean by avoiding clutter with too many files or subdirectories.

Example Code

Here’s an example of how you can structure a simple Python package using the above guidelines:

# myproject/__init__.py
from .main import main

def hello_world():
    print("Hello, World!")

# myproject/main.py
def main():
    print("My Project Main Function")

if __name__ == "__main__":
    main()

# myproject/tests/test_main.py
import unittest
from myproject.main import main

class TestMainFunction(unittest.TestCase):
    def test_main(self):
        # Test the main function
        pass

if __name__ == "__main__":
    unittest.main()

By following these guidelines and best practices, you can create a well-structured Python project that is easy to maintain, scalable, and friendly to IDEs and source control systems.