13. Porting Python to a new platform

The first step is to familiarize yourself with the development toolchain on the platform in question, notably the C compiler. Make sure you can compile and run a hello-world program using the target compiler.

Next, learn how to compile and run the Python interpreter on a platform to which it has already been ported; preferably Unix, but Windows will do, too. The build process for Python, in particular the Makefile in the source distribution, will give you a hint on which files to compile for Python. Not all source files are relevant: some are platform specific, others are only used in emergencies (e.g. getopt.c).

It is not recommended to start porting Python without at least medium-level understanding of your target platform; i.e. how it is generally used, how to write platform specific apps, etc. Also, some Python knowledge is required, or you will be unable to verify that your port is working correctly.

You will need a pyconfig.h file tailored for your platform. You can start with pyconfig.h.in, read the comments, and turn on definitions that apply to your platform. Also, you will need a config.c file, which lists the built-in modules you support. Again, starting with Modules/config.c.in is recommended.

Finally, you will run into some things that are not supported on your target platform. Forget about the posix module in the beginning. You can simply comment it out of the config.c file.

Keep working on it until you get a >>> prompt. You may have to disable the importing of site.py by passing the -S option. When you have a prompt, bang on it until it executes very simple Python statements.

At some point you will want to use the os module; this is the time to start thinking about what to do with the posix module. It is okay to simply comment out functions in the posix module that cause problems; the remaining ones will be quite useful.

Before you are done, it is highly recommended to run the Python regression test suite, as described in Running & Writing Tests.