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PScript is a Python to JavaScript compiler, and is also the name of the subset of Python that this compiler supports. It was developed as a part of Flexx (as flexx.pyscript) and is now represented by its own project. Although it is still an important part of Flexx, it can also be useful by itself.


PScript is pure Python and requires Python 2.7 or 3.5+ (including Pypy). It has no further dependencies.

  • pip install pscript, or
  • conda install pscript -c conda-forge

Short example

   from pscript import py2js

   def foo(a, b=2):
      print(a - b)



   var foo;
   foo = function flx_foo (a, b) {
      b = (b === undefined) ? 2: b;
      console.log((a - b));
      return null;

Supported browsers

PScript aims to support all modern browsers, including Firefox, Chrome and Edge. Internet Explorer is in principal supported from version 9, though some constructs (e.g. async and await) do not work in Internet Explorer.

PScript in the wild

To give an idea of what PScript can do, here are some examples in the wild:

  • Obviously, everything built in Flexx uses PScript, see e.g. these examples
  • The front-end of is built in Python using PScript.

Let us know if you know more!


PScript makes use of the liberal 2-clause BSD license. See LICENSE for details.