The Ruby Language

20 min tutorial

https://www.ruby-lang.org/en/documentation/quickstart/

From Python to Ruby

https://www.ruby-lang.org/en/documentation/ruby-from-other-languages/to-ruby-from-python/

Style guides

https://rubystyle.guide/

https://github.com/airbnb/ruby

Ruby with Sinatra

Basic Webapp

https://roberteshleman.com/blog/2014/06/26/creating-a-basic-web-app-with-ruby-and-sinatra/

Official Sinatra documentation

https://sinatrarb.com/intro.html

Ruby and SQLite

Queries

https://zetcode.com/db/sqliteruby/queries/