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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 file names and source line numbers
  • 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: .


First release! Extensive tests on both Windows and Linux have lead to the conclusion that Transcrypt is ready for production use. Any remaining bugs can reported as GitHub issues at: .

What’s new

  • Multi0level sourcemaps and annotated target code
  • Status moved to Production/Stable

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

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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.

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