Idle — Idle watcher

class Idle(loop, callback[, data=None, priority=0])
Parameters:
  • loop (Loop) – loop object responsible for this watcher (accessible through loop).
  • callback (callable) – see callback.
  • data (object) – any Python object you might want to attach to the watcher (stored in data).
  • priority (int) – see priority.

Idle watchers trigger events when no other events of the same or higher priority are pending (Prepare, Check and other Idle watchers do not count as receiving “events”).

That is, as long as your process is busy handling sockets or timeouts (or even signals, imagine) of the same or higher priority it will not be triggered. But when your process is idle (or only lower-priority watchers are pending), the idle watchers are being called once per event loop iteration - until stopped, that is, or your process receives more events and becomes busy again with higher priority stuff.

The most noteworthy effect is that as long as any Idle watchers are active, the process will not block when waiting for new events.

Apart from keeping your process non-blocking (which is a useful effect on its own sometimes), Idle watchers are a good place to do “pseudo-background processing”, or delay processing stuff to after the event loop has handled all outstanding events.

See also

ev_idle - when you’ve got nothing better to do…