rezzie: A small library for accessing resources and data shipped with your package without using the pkg_resources API.

Background

Shipping data files with your Bioinformatic Python packages is a typical pattern. There are several ways of accessing these data files, but they can be cumbersome and error-prone. One common approach often recommended on StackOverflow is to use the module's __file__ attribute to find the path of the running script and, from there, find the relative path to the resource. But, this approach is fragile and can easily break if the resource is moved, and it doesn't deal with the case where the resource is in a zip file. Another approach is to use the pkg_resources API. But, that module is substantial and has a lot of dependencies, which can cause significant startup times for your command-line tools.

A third-party package called importlib_resources provides a nice API to deal with this problem, and in more recent versions of (Python ≥3.9), it has become part of the standard library and is built on the importlib.resource API of the standard library.

Here, we provide a simple library that has a single function to access the path to any resource shipped with your package. The function returns a pathlib.Path object. You can then read the contents of the file, pass it to a subprocess routine, or do anything else you may need or want to do. We have made it so that it transparently supports versions of Python ≥3.7. When using versions of Python ≥3.9, it uses the standard library importlib_resources API. Otherwise, it uses the importlib_resources package. It will only install the importlib_resources package if the Python version requires it. So, it should keep things lean if you use a recent Python version.

For that reason and many more, we recommend using Python ≥3.10. There are significant performance improvements in the standard library importlib API and notable performances in Python overall to warrant the upgrade.

Installation

You can install rezzie from PyPI using pip:

    pip install rezzie

Usage

To use rezzie, you need to have a package that has resources that you want to access. For example, let's say you have a package called my_package that has a resource called my_resource.txt in a folder called data, that you want to access. You can do that using the rezzie API as follows:

    from rezzie import get_path

    resource_path = get_path("my_package", "data", "my_resource.txt")

The get_path function takes two arguments: the name of the package, and the path and name of the resource.

Example

Let's say you have a package called my_package that has a resource called my_resource.txt in a folder called data, that you want to access.

The my_package package has the following structure:

    my_package
    ├── __init__.py
    ├── data
    │   └── my_resource.txt
    └── __main__.py

Your pyproject.toml file should look like this to ensure the data files are packaged correctly (this assumes using setuptools as the build backend):

    [build-system]
    requires = ["setuptools>=42", "wheel"]
    build-backend = "setuptools.build_meta"

    [project]
    name = "my_package"
    
    [tool.setuptools]
    include-package-data = true

    [tool.setuptools.package-data]
    my_package = ["*.txt"]

The my_package/__init__.py file should look like this:

    from rezzie import get_path

    resource_path = get_path("my_package", "data", "my_resource.txt")

Author

Anders Goncalves da Silva (@andersgs)