To install Datasette using Homebrew:

brew tap simonw/datasette
brew install simonw/datasette/datasette

You can confirm that the install worked using:

$ datasette --version
datasette, version 0.46

Datasette plugins need to be installed into the same Python environment as datasette.

The easiest way to install them is to use the new datasette install command:

datasette install datasette-vega

If you want to install them using pip instead you can do this:

/usr/local/opt/datasette/libexec/bin/pip install datasette-vega

Run datasette plugins to see a list of currently installed plugins.