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C Extensions & FFI: Escaping Python for Speed

Overview

C Extensions enable extreme performance: - ctypes: Call C libraries from Python - CFFI: C Foreign Function Interface - Cython: Write C-like Python (compiles to C) - PyPy C API: Integration with PyPy - Implications for ML: NumPy, PyTorch, TensorFlow use C extensions

Key Topics

  1. ctypes - Call C/DLL functions directly
  2. CFFI - More Pythonic C interface
  3. Cython - Mixed Python/C for speed
  4. PyPy Extensions - Using C extensions with PyPy
  5. Performance Patterns - When to use extensions

When to Use C Extensions

Scenario Best Choice
Call existing C library ctypes
Write new C code Cython
Complex C interface CFFI
NumPy-like operations Cython
Maximum performance Cython + pybind11

Performance Impact

Pure Python:     1x (baseline)
NumPy:          10-100x (C-optimized)
Numba JIT:      100-1000x
Cython:         10-100x
ctypes:         Similar to Cython
CFFI:           Similar to Cython