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Compatibility

zloop aims to be a faithful asyncio.AbstractEventLoop. This page is the honest map of what's supported.

Supported

These work, and are tested (zloop runs uvicorn's full suite, plus its own at 100% coverage):

Area Methods
Scheduling call_soon · call_later · call_at · call_soon_threadsafe · time
Lifecycle run_until_complete · run_forever · stop · is_running · is_closed · close
Futures & tasks create_future · create_task · set_task_factory · get_task_factory
I/O readiness add_reader · remove_reader · add_writer · remove_writer
Servers & connections create_server · create_unix_server · create_connection
Name resolution getaddrinfo · getnameinfo
Executors run_in_executor · set_default_executor · shutdown_default_executor
Signals add_signal_handler · remove_signal_handler (main thread)
Errors & debug call_exception_handler · set_exception_handler · get_exception_handler · default_exception_handler · set_debug · get_debug
Shutdown shutdown_default_executor · shutdown_asyncgens (a safe no-op; zloop tracks no asyncgens)
TLS create_server(ssl=...) · create_connection(ssl=...)

The full TCP socket Transport interface is implemented too (write, writelines, close, abort, pause_reading/resume_reading, write_eof, flow-control limits, get_extra_info, …) - see Transports.

Partially supported

  • create_connection honors local_addr. Some less-common parameters (happy_eyeballs_delay, interleave, all_errors) are accepted but not yet acted on.
  • TLS timeouts - create_server(ssl=...) / create_connection(ssl=...) work, but a couple of the timeout knobs (ssl_handshake_timeout on the server-accept path, ssl_shutdown_timeout) are accepted and not yet wired through to sslproto.

Not implemented

These raise NotImplementedError (most are inherited AbstractEventLoop stubs):

  • The low-level sock_* coroutine helpers - sock_recv, sock_recv_into, sock_sendall, sock_connect, sock_accept, sock_sendfile, … Most programs use the higher-level streams/transports instead.
  • loop.start_tls() - the standalone upgrade-an-existing-transport API. (Note: create_server/create_connection with ssl= are supported - this is the separate start_tls method.)
  • sendfile (loop.sendfile), create_unix_connection, and connect_accepted_socket.
  • Datagram / UDP (create_datagram_endpoint) and pipes / subprocess transports (connect_read_pipe, connect_write_pipe, subprocess_exec, subprocess_shell).
  • Windows - zloop is kqueue/epoll only. (IOCP is a different I/O model.)

Platforms & Python versions
Python CPython 3.12+
macOS / BSD ✅ via kqueue
Linux ✅ via epoll
Windows ❌ not supported

A word on honesty

This page lists what isn't done as plainly as what is. zloop's goal is to be a trustworthy drop-in for the common case (ASGI servers, HTTP clients, structured concurrency) - not to claim 100% of asyncio's surface on day one. If you hit a gap that matters to you, open an issue.