A directory of Python files (essentially, a module) can be packaged into a .pyz file—a .zip -format archive—and given to someone else who has the Python runtime.

Devs unknowingly use “malicious” modules snuck into official Python repository Code packages available in PyPI contained modified installation scripts.

Cython generates the second kind of module: C libraries that talk to Python’s internals, and that can be bundled with existing Python code. Cython code looks a lot like Python code, by design.