04 Dec 2014

Distutils with resource files

I had a little university homework with Tegi to create a GUI for rsync. We used PyQt5 and Python3 to do the job and the result can be found here. It won’t create peace or more cute animgifs, but it’s ours and we could learn some new things from it.One of them was using distutils and resource files together.

Problem

I wanted to use QML resource files in this project and reference them with their relative path to the project’s root directory in my runner script.

The problem is, when I install this little program, the runner script ends up in a bin directory somewhere on my computer. It can import the yarg package, but it won’t find the *.qml files, because it tries to locate them with their relative paths, as if they were in the development environment.

Solution

You can check the layout of this project: * all python files are under yarg/ package * all QML files are under yarg/resource/ * a main program is a script called runner.py (in the repo’s root dir), which references a QML with path: yarg/resource/main.qml

The following things are needed to solve this problem: * in setup.py, I use data_files to tell distutils, what are my resource files:

 data_files=[('resource', ['yarg/resource/main.qml'])],

• there is also a package_data line, which defines the resources needed by the yarg package:

 package_data={'yarg': ['resource/*']},

• the find_packages() function is required, because distutils won’t copy all Python packages into the EGG,
• in my runner script, I use the pkg_resources module, to access to the resource files bundled in a single EGG file, which is a simple compressed file with a specific directory and file layout and some meta files. When you use pkg_resouces, it will decompress your resources in a temporary directory and tells you the location of this place:

  import pkg_resources
  ...
  # This will decompress the whole yarg/resource directory into a temp. dir. and returns
  # the path of that dir.
  # I need this, because my root QML file (main.qml) imports the others next to it.
  pkg_resources.resource_filename('yarg', 'resource')
  ...
  # This function returns the path of the yarg/resource/main.qml files.
  pkg_resources.resource_filename('yarg.resource', 'main.qml')

And now, I’m able to use the same code in development and after installation. pkg_resources will find the most appropriate locations.

Till next time,
Tibor Benke at 23:00