cffi

cffi stands for the C Foreign Function Interface for Python. It is a library that provides a direct way to call C code from Python, offering an alternative to ctypes with an emphasis on simplicity, safety, and performance. cffi is designed to wrap existing C libraries and to expose their functionality to Python without requiring hand-written C extension modules.

cffi provides two main usage modes. In API mode, you write C declarations describing the C APIs you want to access and optionally include C source code; cffi then builds a Python extension module that exposes the declared functions and types. In ABI mode, you declare the same C interfaces and load an existing shared library at runtime with ffi.dlopen, obtaining callable wrappers for the functions without compiling new C sources. Both modes rely on libffi to generate the necessary wrappers, ensuring relatively portable and efficient call paths.

Key features include support for C data types such as pointers, arrays, structs, unions, enums, and function pointers, as well as the ability to create and manipulate C data from Python (via ffi.new and memory buffers) and to define Python-callable C callbacks. cffi also handles type conversions between Python and C and provides facilities for working with variadic functions to a practical extent.

Compared with ctypes, cffi generally offers a more straightforward declaration syntax and more robust handling of complex C types, while avoiding some of ctypes’ more brittle aspects. While not a full replacement for all C++ bindings, cffi is widely used for binding to C libraries and for projects that want low-overhead, maintainable bridges between Python and C.

The project is open source and is maintained to prioritize portability and ease of use within the Python ecosystem.