Skip to main content

Python to JavaScript transpiler, supporting multiple inheritance and generating lean, highly readable code

Project description

Transcrypt is a tool to precompile a fairly extensive subset of Python into compact, readable Javascript. It has the following characteristics:

  • Allows for classical OO programming with multiple inheritance using pure Python syntax, parsed by CPython’s native parser

  • Seamless integration with the universe of high-quality web-oriented JavaScript libraries, rather than the desktop-oriented Python ones

  • Hierarchical URL based module system to prevent name conflicts

  • Simple relation between Python source and generated JavaScript code for easy debugging

  • Multi-level sourcemaps and optional annotation of target code with source references

  • Compact downloads, kB’s rather than MB’s

  • Lightning fast JavaScript code, using memoization (call caching) to optionally bypass the prototype lookup chain

  • Operator overloading can be switched on and off locally to facilitate use for numerical math that’s both readable and efficient


Transcription once used to be manual labour

Documentation with code examples

Take a look at the documentation with code examples at the Transcrypt website: .


Release 4 (version 3.5.161):

  • Almost all of the math module and most important part of random module added

  • Most important part of turtle module added. Uses SVG, see editable examples at:

  • Multi-level sourcemaps, annotated target code, virtualenv installation.

  • Automated tests of functionality of compiled code OK.

  • Manual tests of sourcemaps and random module OK.

  • Further tests and feedback very welcome.

  • Sourcemaps were tested on Chrome under Windows and Linux, but seem to work on Firefox under Linux as well.

What’s new

  • Aliases added: case translates to py_case, default translates to py_default (switch already translated to py_switch)

  • Readme adapted

  • Fixes for wrong evaluation order when using // (issue 50) and for error in set and array compare (issue 15)

  • Bug in random module fixed

  • Bug in Linux compilation path fixed

  • Python random module added, only most important functionality: seed, randint, choice, random

  • Python math module added, almost all functionality

  • Live on-line SVG based turtle graphics added to website + demo’s

  • Turtle graphics improved and expanded

  • SVG based turtle graphics module added

  • Multiple module initialization bug fixed

  • Alias py_name (in JS) for name (in Python) added

  • Installation procedure changed to benefit from virtualenv

  • Optional annotation of target code with source file names and source line numbers

  • Multi-level sourcemaps: Python source level debugging of both formatted and minified JavaScript code

  • Source code included in map rather than separate as was the case earlier

  • Switched from sectored V3 sourcemaps to monolithic V3 sourcemaps since they seem more mature and accepted

Known restrictions

  • No standard libs, use or encapsulate the JavaScript ones, that’s part of the concept. Some may be ported though.

  • Not all methods of builtin types are there by default. This results from a deliberate choice to keep Transcrypt lean. Such things can be distributed in separate libs.

  • No eval and exec of Python code. This is again part of the concept. Transcrypt code is compiled, optimized and minified in advance to warant fast page loads.

  • No threading of any kind. Will probably stay that way as long as JavaScript doesn’t properly support that.

  • No iterator, generator, xrange stuff. Maybe in the future if a broadly installed version of JavaScript suppports it.

Known bugs

  • None


As can be seen below, there’s a simple parallel between the Python and the JavaScript code. So it should be easy to debug. Also, code can be tested from the command prompt using stubs.

Screenshot of Python versus JavaScript code

Classic OO with multiple inheritance in JavaScript

Other packages you might like


Copyright 2014, 2015, 2016 Jacques de Hooge, GEATEC engineering,

Licensed under the Apache License, Version 2.0 (the “License”); you may not use this file except in compliance with the License. You may obtain a copy of the License at

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Project details

Release history Release notifications | RSS feed

Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Source Distribution (11.8 MB view hashes)

Uploaded Source

Supported by

AWS AWS Cloud computing and Security Sponsor Datadog Datadog Monitoring Fastly Fastly CDN Google Google Download Analytics Microsoft Microsoft PSF Sponsor Pingdom Pingdom Monitoring Sentry Sentry Error logging StatusPage StatusPage Status page