cpy3x 0.1.0

What is cpy3x?

cpy3x is a golang package, which is a wrapper around the python c API. This library assists the usage of python c API in golang, by exposing the the python c API through CGO.

What versions of python c API are supported?

Currently cpy3x supports python versions starting from 3.5.x till 3.10.x. It has multiple packages named as follows:

  • pycore – This package contains the APIs that are either part of Limited API or those APIs are common across versions 3.5-3.10.
  • py35 – Contains APIs and unit-tests specific to python version 3.5
  • py36 – Contains APIs and unit-tests specific to pythoh version 3.6
  • py37 – Contains APIs and unit-tests specific to pythoh version 3.7
  • py38 – Contains APIs and unit-tests specific to pythoh version 3.8
  • py39 – Contains APIs and unit-tests specific to pythoh version 3.9
  • py310 – Contains APIs and unit-tests specific to pythoh version 3.10

The main reason behind this approach of separating version specific APIs in different packages is to make the pycore package a generic one, which contains all the APIs required to build a regular c-python extension, which is compatible across multiple versions. If you use only pycore package in your program, it can be compiled any python version from 3.5 to 3.10.

As new APIs are introduced in the new versions and older APIs keep depricating, we have those version specific APIs in the version specific packages. If you are using a version specific package say py37 along with pycore, then make sure you link the version specific python during compilation.

These packages contain PyXYZ functions and macros of the public C-API of CPython have been exposed. Theoretically, you should be able use https://docs.python.org/3/c-api and know what to type in your go program.

relation to go-python/cpy3

This project is a successor to go-python/cpy3, which only supports python version 3.7. If cpy3x works as expected, I might raise a PR so that it could be merged to cpy3.



We will need pkg-config and a working version specific python3 environment to build these bindings. Make sure you have Python libraries and header files installed as well (python3.7-dev on Debian or python3-devel on Centos for example)..

By default pkg-config will look at the python3 library so if you want to choose a specific version just symlink python-X.Y.pc to python3.pc or use the PKG_CONFIG_PATH environment variable. You can take a look into interpreters folder to check what python3.pc files look like on Ubuntu. For more info on cflags and ldflags check out the documentation.

Go get

Then simply go get github.com/go-python/cpy3x@main


Some functions mix go code and call to Python function. Those functions will return and int and error type. The int represent the Python result code and the error represent any issue from the Go layer.


func PyRun_AnyFile(filename string) open filename and then call CPython API function int PyRun_AnyFile(FILE *fp, const char *filename).

Therefore its signature is func PyRun_AnyFile(filename string) (int, error), the int represent the error code from the CPython PyRun_AnyFile function and error will be set if we failed to open filename.

If an error is raise before calling th CPython function int default to -1.


  • TODO (You can get started by looking at some unittests in each package)

Tutorials and Blogs


View Github