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Python Academy · Lesson

Why C Extensions? Use Cases and Trade-offs

Understand when and why to extend Python with native C code.

What Is a C Extension?

A C extension is a compiled shared library (.so on Linux/macOS, .pyd on Windows) that Python can import. It exposes functions and types implemented in C.

# After building the extension:
import myext
result = myext.fast_sum([1, 2, 3, 4, 5])
print(result)   # 15 (computed in C)

When to Use C Extensions

Use C extensions for: CPU-bound numerical loops, wrapping existing C libraries, bypassing the GIL for multi-threaded workloads, or achieving extreme memory efficiency.

# Good candidates for C extensions:
# - NumPy array operations
# - Image processing pixel loops
# - Cryptographic primitives
# - Wrapping libpng, libssl, sqlite3

All lessons in this course

  1. Why C Extensions? Use Cases and Trade-offs
  2. ctypes: Calling C Libraries from Python
  3. cffi: C Foreign Function Interface
  4. Writing a Python C Extension Module
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