Welcome To Lighning Python

Lightning Python is a project seeking to provide an implementation of CPython (the reference implementation) compiled using the Open Watcom compiler. Originally meant to provide a port of Python for Windows compiled with Open Watcom, the project is being extended to more generally encompass compiling Python using the Open Watcom toolchain regardless of platform.

As this port is "in progress," a number of standard library modules may not be implemented if they use C extensions. The specifics are covered for each platofm below.

The name "Lightning" just references the logo for Open Watcom. It does not imply Lightning Python is faster than stock Python. In fact, it is considerably slower at this moment on Windows.


In general terms, Lightning Python for Windows is complete with a few exceptions. At the moment, SQLite, hashlib, and tkinter are all absent; these missing modules will be implemented in the future.
Furthermore, there may be bugs in the interpretter itself. The standard library's regression test suite fails or outright crashes in a number of locations. Crashes are most likely due to a problems with cffi.

Python 3.4 is currently supported on Windows.


The Linux port is actually relatively straightforward and functional. However, Open Watcom lacks support for shared objects under Linux. Due to this missing feature, the interpreter must be statically linked, and a number of native modules are currently not included in the build.

Python 3.5 is currently supported on Linux.


To build Python, you'll first need to acquire Open Watcom. The unofficial version 2.0 fork is necessary as it implements a number of modern Windows API and C runtime calls that are not available in the last official release (from over two years ago).

The builds of the Open Watcom compiler can be downloaded from links on the project's GitHub page:

Alternatively, nightly binaries are available as simple archives from:

Once Open Watcom is installed, you'll need to acquire the source to Lightning Python.


After downloading the source, the project "python.wpj" in the "OWbuild-Windows" directory should be opened using the Open Watcom IDE. The target "python34.dll" should be built first as most everything else relies on it. Next, it is suggested that the "python.exe" target should be built. Finally, the remaining DLL projects, which are subsequently copied into the appropriate pyd files, can be built.

The Windows port also includes a distribution system for generating a true MSI installer in the LRelease-Windows directory.


After downloading an appropriate source distribution, you'll need to first apply the needed patch from Patches/. Next, copy the build script from OWbuild-Linux/ to the root of the Python source tree. Finally, execute and wait a minute or two for the interpreter to be built. More details are at OWbuild-Linux/


Lightning Python is generally compatible with stock Python, excpeting missing native modules as pointed out earlier.


Lightning Python is hosted on bitbucket, where you can find the bug tracker, a wiki, and downloads:

The current lead, Jeff Armstrong, is available at:

Twitter: @fortranjeff