Dynamic Versioning: A Guide To Pyproject.toml

Hey guys! Let's dive into dynamic versioning in pyproject.toml. Dynamic versioning allows you to define your Python package's version based on runtime information, such as the current date or any other dynamic data. This is super useful for automating your version management and keeping things smooth.

Configuration Steps

To get dynamic versioning working in your pyproject.toml, follow these steps:

Define the Version Dynamically in Your Code

First, in your package's __init__.py, you need to define the version dynamically. Here's how you can do it:

__version__ = f"{1}.{2}.{3}"  # Replace with your dynamic logic

Make sure you replace {1}.{2}.{3} with your actual dynamic logic. This could involve fetching data from an external source, calculating a version based on the current date, or any other method that suits your needs.

Set Up pyproject.toml

Next up, your pyproject.toml should include the following sections:

[project]
name = "your_package_name"
dynamic = ["version"]

[build-system]
requires = ["setuptools>=61.0.0", "setuptools-scm"]
build-backend = "setuptools.build_meta"

[tool.setuptools.dynamic]
version = { attr = "your_package_name.__version__" }

Let's break this down:

• [project] section:
  • name: This is where you put the name of your package. Make sure it matches the name you've chosen.
  • dynamic: This array tells setuptools that the version field will be determined dynamically.
• [build-system] section:
  • requires: This specifies the dependencies needed to build your package. setuptools>=61.0.0 and setuptools-scm are essential for dynamic versioning.
  • build-backend: This tells setuptools to use its build meta backend.
• [tool.setuptools.dynamic] section:
  • version: This is where you link the version in your pyproject.toml to the __version__ attribute in your Python code. The attr key specifies the path to this attribute.

Important Considerations

When dealing with dynamic versioning, there are a few key things to keep in mind. These considerations can help you avoid common pitfalls and ensure a smooth build process.

Static vs. Dynamic Versioning

It's crucial to understand the difference between static and dynamic versioning. If you set the version as a static string (e.g., __version__ = "1.2.3"), it's straightforward. Setuptools will simply use this value. However, when you use a dynamic expression (like a function call), setuptools needs to execute that expression during the build process. This is where things can get tricky.

For example, if you have:

__version__ = get_dynamic_version()

and get_dynamic_version() involves complex logic or external dependencies, it might lead to errors during the build. Make sure your dynamic logic is simple and doesn't rely on unavailable resources during the build.

Handling Build Errors

If you encounter build errors, the first step is to carefully examine the error message. Common errors include AttributeError or ModuleNotFoundError. These errors usually indicate that the attribute you referenced in pyproject.toml is either not defined correctly or not accessible during the build process. The build system needs to access this attribute at build time, so ensure it is available.

To troubleshoot, double-check the following:

1. Attribute Path: Verify that the attr value in your pyproject.toml is correct. It should accurately point to the __version__ attribute in your package. For example, if your package is named my_package and __version__ is defined in my_package/__init__.py, the attr should be my_package.__version__.
2. Code Execution: Ensure that the code defining __version__ can be executed without errors during the build process. This means that any dependencies required to calculate the version must be available when setuptools is building the package.
3. Circular Dependencies: Avoid circular dependencies that might prevent setuptools from accessing the __version__ attribute. Circular dependencies occur when two or more modules depend on each other, creating a loop that can prevent proper initialization.

Best Practices for Dynamic Versioning

To make your life easier, here are some best practices for dynamic versioning:

• Keep It Simple: Avoid overly complex logic in your dynamic versioning code. Simpler code is easier to debug and less likely to cause build errors.
• Isolate Dependencies: If possible, isolate the code that calculates the version from the rest of your package. This reduces the risk of dependency conflicts during the build.
• Test Thoroughly: Always test your build process to ensure that the dynamic versioning works as expected. Use tools like tox to test your package in different environments.
• Use setuptools-scm: Consider using setuptools-scm for managing your package version. It automatically determines the version from your Git repository, making dynamic versioning much simpler.

Example with setuptools-scm

To use setuptools-scm, first, install it:

pip install setuptools-scm

Then, update your pyproject.toml:

[project]
name = "your_package_name"
dynamic = ["version"]

[build-system]
requires = ["setuptools>=61.0.0", "setuptools-scm"]
build-backend = "setuptools.build_meta"

[tool.setuptools_scm]

With this setup, setuptools-scm will automatically determine the version from your Git tags. You no longer need to define __version__ in your code.

References and Further Reading

For more information, check out these resources:

• setuptools Documentation
• tox Configuration

By following these steps and keeping the important considerations in mind, you can effectively implement dynamic versioning in your pyproject.toml. This will help you automate your version management and ensure that your package always has the correct version.