My personal configuration for waybar I will do my best to comment the configuration file. Feel free to crib/steal this for your own personal use.
For the bundled mediaplayer.py (this is from waybar) to work,
You must have gobject-introspection installed from your package manager so that you can install PyGObject with pip.
If you're on Arch Linux, you can directly install pacman -S python-gobject.
NOTE: If you use a Python version manager, such as asdf, installing python-gobject MAY NOT work.
This is because installing python-gobject installs it globally, and your versioned Python will have it's own pip and package directory.
If that's the case, then pip install PyGObject would be the way to go.
That being said, running waybar in sway will use the system Python, unless you set it up to use your version manager Python.
Run ./install.sh to link the configuration files to the proper location