gevent.hub
- Event-loop hub¶get_hub
(*args, **kwargs)¶Return the hub for the current thread.
If a hub does not exist in the current thread, a new one is
created of the type returned by get_hub_class()
.
Hub
(loop=None, default=None)¶Bases: greenlet.greenlet
A greenlet that runs the event loop.
It is created automatically by get_hub()
.
Switching
Every time this greenlet (i.e., the event loop) is switched to, if
the current greenlet has a switch_out
method, it will be called. This
allows a greenlet to take some cleanup actions before yielding control. This method
should not call any gevent blocking functions.
NOT_ERROR
= (<class 'greenlet.GreenletExit'>, <type 'exceptions.SystemExit'>)¶Instances of these classes are not considered to be errors and do not get logged/printed when raised by the event loop.
SYSTEM_ERROR
= (<type 'exceptions.KeyboardInterrupt'>, <type 'exceptions.SystemExit'>, <type 'exceptions.SystemError'>)¶If instances of these classes are raised into the event loop, they will be propagated out to the main greenlet (where they will usually be caught by Python itself)
backend
= None¶format_context
= 'pprint.pformat'¶loop_class
= ['gevent.core.loop']¶resolver
¶resolver_class
= ['gevent.resolver_thread.Resolver', 'gevent.resolver_ares.Resolver', 'gevent.socket.BlockingResolver']¶The class or callable object, or the name of a factory function or class,
that will be used to create resolver
. By default, configured according to
Name Resolution (DNS). If a list, a list of objects in preference order.
threadpool
¶threadpool_class
= ['gevent.threadpool.ThreadPool']¶threadpool_size
= 10¶handle_error
(context, type, value, tb)¶Called by the event loop when an error occurs. The arguments
type, value, and tb are the standard tuple returned by sys.exc_info()
.
Applications can set a property on the hub with this same signature to override the error handling provided by this class.
Errors that are system errors
are passed
to handle_system_error()
.
Parameters: | context – If this is None , indicates a system error that
should generally result in exiting the loop and being thrown to the
parent greenlet. |
---|
handle_system_error
(type, value)¶print_exception
(context, type, value, tb)¶switch
()¶switch_out
()¶wait
(watcher)¶Wait until the watcher (which should not be started) is ready.
The current greenlet will be unscheduled during this time.
See also
gevent.core.io
, gevent.core.timer
,
gevent.core.signal
, gevent.core.idle
, gevent.core.prepare
,
gevent.core.check
, gevent.core.fork
, gevent.core.async
,
gevent.core.child
, gevent.core.stat
cancel_wait
(watcher, error)¶Cancel an in-progress call to wait()
by throwing the given error
in the waiting greenlet.
run
()¶Entry-point to running the loop. This method is called automatically when the hub greenlet is scheduled; do not call it directly.
Raises LoopExit: | |
---|---|
If the loop finishes running. This means that there are no other scheduled greenlets, and no active watchers or servers. In some situations, this indicates a programming error. |
join
(timeout=None)¶Wait for the event loop to finish. Exits only when there are no more spawned greenlets, started servers, active timeouts or watchers.
If timeout is provided, wait no longer for the specified number of seconds.
Returns True if exited because the loop finished execution. Returns False if exited because of timeout expired.
destroy
(destroy_loop=None)¶Waiter
(hub=None)¶Bases: object
A low level communication utility for greenlets.
Waiter is a wrapper around greenlet’s switch()
and throw()
calls that makes them somewhat safer:
get()
method currently;switch()
and throw()
switch()
/throw()
is called before the receiver calls get()
, then Waiter
will store the value/exception. The following get()
will return the value/raise the exception.The switch()
and throw()
methods must only be called from the Hub
greenlet.
The get()
method must be called from a greenlet other than Hub
.
>>> result = Waiter()
>>> timer = get_hub().loop.timer(0.1)
>>> timer.start(result.switch, 'hello from Waiter')
>>> result.get() # blocks for 0.1 seconds
'hello from Waiter'
If switch is called before the greenlet gets a chance to call get()
then
Waiter
stores the value.
>>> result = Waiter()
>>> timer = get_hub().loop.timer(0.1)
>>> timer.start(result.switch, 'hi from Waiter')
>>> sleep(0.2)
>>> result.get() # returns immediatelly without blocking
'hi from Waiter'
Warning
This a limited and dangerous way to communicate between
greenlets. It can easily leave a greenlet unscheduled forever
if used incorrectly. Consider using safer classes such as
gevent.event.Event
, gevent.event.AsyncResult
,
or gevent.queue.Queue
.
ready
()¶Return true if and only if it holds a value or an exception
successful
()¶Return true if and only if it is ready and holds a value
switch
(value=None)¶Switch to the greenlet if one’s available. Otherwise store the value.
throw
(*throw_args)¶Switch to the greenlet with the exception. If there’s no greenlet, store the exception.
get
()¶If a value/an exception is stored, return/raise it. Otherwise until switch() or throw() is called.
Next page: gevent.core
- event loop based on libev