Blockly that's more Python than JavaScript, powered with Skulpt
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acbart Merge pull request #35 from isnullxbh/hotfix/math-functions
ceil/floor functions from the Python math library
Latest commit 76ee192 Apr 12, 2018
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advertising New instructor API features Mar 4, 2017
blockly Properties=>Variables, Tifa improvements Jan 1, 2018
closure-library Updated codemirror Jun 22, 2015
docs Adding docs, removing bad old code Mar 26, 2017
fonts Upgrade bootstrap, hide/show settings menu May 8, 2017
images Fix +/- for tuples, separate blockly blocks Jun 24, 2017
libs AI improvements, callback fixed, skulpt file i/o Jul 25, 2017
skulpt NodeJS fixes Feb 4, 2018
src @feature(py2block) added cases for making blocks for floor/ceil func… Apr 12, 2018
tests Fixes for Upload mode Sep 13, 2017
.gitignore Node for gitiginore Oct 31, 2017
.gitmodules Initial building Oct 20, 2014
LICENSE Initial commit May 13, 2014 Update Aug 25, 2016
blockpy_new.html NodeJS fixes Feb 4, 2018 More Tifa bindings Jan 28, 2018
canvas_frame.html Major revisions for v3 May 11, 2016
engine_test.html Tifa improvements, properties=>variables, engine only mode Jan 10, 2018 Upload mode, corgis integration, uploading block images Aug 9, 2016
iframe_test.html Glyphicon fonts, alternative layout Jun 25, 2015 PAISC supports list comprehensions Sep 26, 2017
makefile New PYAIJS and Instructor stuff Oct 22, 2017 Add pytifa to, and new function_prints test Jan 20, 2018
package-lock.json NodeJS fixes Feb 4, 2018
package.json NodeJS fixes Feb 4, 2018
replay.html Created some utility functions Dec 6, 2017
server.js NodeJS fixes Feb 4, 2018
todo.txt New instructor API features Mar 4, 2017
treeCompTest.html Updates to some tests. Feb 28, 2018



BlockPy is a web-based Python environment that lets you work with blocks, text, or both. Designed for Data Science and equipped with powerful tools like the State Explorer and Guided Feedback, the goal of BlockPy is to let you solve authentic, real-world problems.

The goal of BlockPy is to give you a gentle introduction to Python but eventually mature you into a more serious programming environment (such as Spyder or PyCharm). Long-term, we may support some game/animation design stuff that Scratch/Snap does, but that's not the real goal.

The BlockPy project is aimed at solving some hard technical problems: having a block-based environment for a dynamic language can be tricky - are a given pair of square brackets representing list indexing or dictionary indexing? Our goal is to use advanced program analysis techniques to provide excellent support to learners.


The core architecture of BlockPy is a synthesis of:

  • Blockly: a visual library for manipulating a block canvas that can generate equivalent textual code in a variety of languages
  • Skulpt: an in-browser Python-to-JavaScript compiler/intepreter, that aims to emulate the full language with precision if not speed.

By combining these two technologies, we end up with a powerful system for writing Python code quickly. Everything is meant to run locally in the client, so there's no complexity of sandboxing students' code on the server.

The major innovations are:

  • PythonToBlocks: by parsing the AST generated by Skulpt, we can build equivalent Blockly code, effectively allowing round-trips between text and blocks.
  • CORGIS Datsets: new blocks access real-world datasets (although currently these are only cached versions, for performance reasons).
  • Interactive Guided Problems: Problem text is given to students, along with teacher provided code that can do analysis on the students' code and make suggestions (e.g., observing that they haven't printed anything yet).
  • Data Explorer: The data explorer allows users to walk through their code.


First, clone it locally. This could take a little while.

> git clone

You'll need to build Skulpt and Blockly. Both of these depend on the Closure Compiler, so you'll need to put that in the empty closure-library folder. You can follow the [Blockly instructions here] ( , but the gist will be:

> wget -O
> unzip

CD into the new blockpy directory

> cd blockpy/

And add the relevant subtree information to your .git/config:

> vi .git/config

Replace the contents of that file with the information found here: (TODO: show the actual commands used to set this)

Next, you'll need to build Blockly:

> cp blockly/msg/en.js en.js
> cd blockly
> python
> cd ..
> mv en.js blockly/msg/en.js

And then you'll build Skulpt:

> cd skulpt
> python dist
> cd ..

If you are on windows, you may encounter the message "No gzip executable", you can safely ignore this.

And now you should be able to try out the example file!

> start blockpy_new.html

The server has its own requirements.txt and uses a python runserver

If you make edits to either Blockly or Skulpt, you'll need to rerun their build commands. Simiarly, if you edit src/interface.html than you'll need to rebuild it:

> python

Otherwise, you should be able to edit the src/*.js files freely. To get a sense of the dependencies, check out the blockpy_new.html file and then the src/main.js file. These should be good starting points.


Both Blockly and Skulpt are subtrees.

Push changes to the subtrees' repos:

> git subtree push --prefix=skulpt/ --squash skulpt master
> git subtree push --prefix=blockly/ --squash blockly master
> git subtree push --prefix=server/ --squash server master
> git subtree push --prefix=server/static/blockly-games --squash blockly_games master

Pull changes from upstream repos (e.g., official Blockly and Skulpt, our production server):

> git subtree pull --prefix=skulpt --squash skulpt_upstream master
> git subtree pull --prefix=blockly --squash blockly_upstream master
> git subtree pull --prefix=server --squash server master
> git subtree pull --prefix=server/static/blockly-games --squash blockly_games master

Note: if you get an error about a "fatal entry", make sure you don't have a trailing slash on the prefix!