Get started with Python / GTK3 / PyGObject in Ubuntu

 I found myself needing to make a GUI tool for work using a recent version of Ubuntu. These are the steps I followed.

*Install Ubuntu packages needed

sudo apt install pkg-config libglib2.0-dev libgtk-3-dev libgirepository1.0-dev;

You should already have python3 by default.

Note, in Ubuntu 20 you may also need these packages as well for the pycairo/wheels dependency:

sudo apt install libcairo2-dev python3-dev;

*Create a virtual env and set permissions

(Note: You will need to install the package for pip3 for python 3 if it is not already installed)

Choose a location on your machine to hold your python virtualenv, e.g mine will be "/opt/python3".

Find your python 3 path, e.g.

which python3

- mine is /usr/bin/python3

pip3 install virtualenv;

sudo mkdir -p /opt/py3env;

sudo chown scott:scott -R /opt/py3env;

sudo chmod 777 -R /opt/py3env;

virtualenv -p /usr/bin/python3 /opt/py3env;

*Start using the new virtualenv

source /opt/py3env//bin/activate;

pip install --upgrade pip

*Install PyGObject in the virtualenv

pip install pygobject

See the output: 

Successfully installed pycairo-1.20.0 pygobject-3.38.0

*Try a "hello world" program

Save this code in an editor, e.g. as a file named "hello_world.py": 

#!/usr/bin/env python

import gi

gi.require_version("Gtk", "3.0")

from gi.repository import Gtk

window = Gtk.Window(title="Hello World")

window.show()

window.connect("destroy", Gtk.main_quit)

Gtk.main()

*Run the program on the command line:

python hello_world.py

You should see a small GUI window appear! (You might need to stretch it to see its title bar "Hello World")