Python & FastAPI•Part 3: Asynchronous Programming & Concurrency (26 - 40)
I/O Multiplexing (`epoll` / `kqueue`):
In Simple Words: OS kernel primitives that monitor thousands of file descriptors and network sockets, waking up the Python event loop only when a socket has data ready to read/write.
python
# Low-level selectors module wrapping epoll/kqueue:
import selectors, socket
sel = selectors.DefaultSelector() # Uses epoll on Linux, kqueue on macOS
server = socket.socket()
server.bind(('localhost', 9000))
server.listen()
server.setblocking(False)
sel.register(server, selectors.EVENT_READ, data=None)