CFFI — C Foreign Function Interface for Python

CFFI (C Foreign Function Interface) lets Python code call C libraries by declaring C-like function signatures and types that can often be copy-pasted directly from header files. It supports four modes: ABI/API level each with inline or out-of-line (pre-compiled) preparation. The current stable release is 2.0.0 (released September 2025), requiring Python >=3.9. It is the recommended way to interface with C on PyPy and is used as a foundation by cryptography, bcrypt, and many other major Python packages.