Interactive notebooks ~ Pluto.jl | Fons van der Plas | JuliaCon 2020

Fons van der Plas introduces Pluto.jl, a reactive notebook system for Julia that automatically updates cells based on a dependency graph.

Introducing a fresh, new notebook system for rapid prototyping! Pluto understands global references between cells, and reactively re-evaluates cells affected by a code change. At JuliaCon, we will show how Pluto can liven up your workflow. Whether you’re a scientist, a finance professional or an engineer, you use notebooks like Jupyter to tell a story. You fiddle a bit with your code, running cells here and there, and when you’re done - you restart the kernel and keep your fingers crossed that it’ll all work together when you press “run all”. 🙋 In Pluto, things work differently. When you change a variable, Pluto automatically re-runs the cells that refer to it. And when you delete a cell, the variables, methods and imports from the old code disappear. Unlike Jupyter or Matlab, there is no mutable workspace, but rather a one-to-one correspondence between variables and code. 🚨 Reactivity is not just fun for mathematical tricks! It guarantees that the code you see exactly matches the variables you're working with, eliminating bugs before you even knew you had them. ⚡ Your notebook becomes interactive by splitting your code into multiple cells! Changing one cell instantly shows effects on all other cells, giving you a fast and fun way to experiment with your model. And to really spice up your notebook, you can use HTML sliders, or even custom JavaScript widgets, to drive your Julia variables. Change λ = 5 to @bind λ Slider(1:10), and all cells that use λ are controlled by a slider. 💾 Notebooks are saved as pure Julia files and can be exported as rich documents with cell output to HTML or PDF. By separating source code and output, you can take full advantage of git for version control and you can import Pluto notebooks as if they are written in a regular editor. After a live demo, the second part of the talk will unveil some of the tricks that power Pluto. The core concepts are: - static code analysis to find global definitions and references in cells; - directed graph of cells, which tells Pluto which cells to run, in which order; - managed workspace for code to live in, and cleaning the workspace in milliseconds; - responsive connection between JavaScript clients and Julia. Pluto is written in pure Julia, which comes with two benefits: first, it’s easily installable as a package without requiring Python - you only need Julia and a web browser. Second, it is ready to be improved by Julia developers who we hope to inspire at the conference. Pluto is an exciting project to work on, and we are eager to hear your ideas! Resources Pluto.jl home page: plutojl.org/ Pluto.jl repository: github.com/fonsp/Pluto.jl Contents 00:00 Opening 00:19 Introduction 00:42 Why we made Pluto? 01:06 Programming is easy, programming languages are powerful, but our environments are 70s vintage 01:47 Jupyter notebooks: strong points and pain points 02:23 Alternatives to Jupyter 03:09 Enter Pluto. Live demo 06:00 Pluto doesn't allow multiple expressi