Where to find geckodriver needed by Selenium Python package?

Find the latest release for your OS.

Extract it, and copy geckodriver to /usr/local/bin -- so if v0.11.1 was the most recent version, and you were on 64bit linux, you'd do this:

wget https://github.com/mozilla/geckodriver/releases/download/v0.11.1/geckodriver-v0.11.1-linux64.tar.gz
tar -xvzf geckodriver-v0.11.1-linux64.tar.gz
rm geckodriver-v0.11.1-linux64.tar.gz
chmod +x geckodriver
cp geckodriver /usr/local/bin/