Jupyter - Project Jupyter exists to develop open-source software, open-standards, and services for interactive computing across dozens of programming languages. Ready to get started? Try it in your browser Install the Notebook.
Evernote - Bring your life's work together in one digital workspace. Evernote is the place to collect inspirational ideas, write meaningful words, and move your important projects forward.
Boostnote - Boostnote is an open-source note-taking app.
Joplin - Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. The notes are searchable, tagged and modified either from the applications directly or from your own text editor.
iPython - iPython provides a rich toolkit to help you make the most out of using Python interactively.
Google Keep - Capture notes, share them with others, and access them from your computer, phone or tablet. Free with a Google account.