AsyncFuture

from panda3d.core import AsyncFuture

class AsyncFuture

Bases:

Bases: TypedReferenceCount

This class represents a thread-safe handle to a promised future result of an asynchronous operation, providing methods to query its status and result as well as register callbacks for this future’s completion.

An AsyncFuture can be awaited from within a coroutine or task. It keeps track of tasks waiting for this future and automatically reactivates them upon this future’s completion.

A task itself is also a subclass of AsyncFuture. Other subclasses are not generally necessary, except to override the function of cancel().

Until the future is done, it is “owned” by the resolver thread, though it’s still legal for other threads to query its state. When the resolver thread resolves this future using set_result(), or any thread calls cancel(), it instantly enters the “done” state, after which the result becomes a read-only field that all threads can access.

When the future returns true for done(), a thread can use cancelled() to determine whether the future was cancelled or get_result() to access the result of the operation. Not all operations define a meaningful result value, so some will always return nullptr.

In Python, the cancelled(), wait() and get_result() methods are wrapped up into a single result() method which waits for the future to complete before either returning the result or throwing an exception if the future was cancelled. However, it is preferable to use the await keyword when running from a coroutine, which only suspends the current task and not the entire thread.

This API aims to mirror and be compatible with Python’s Future class.

New in version 1.10.0.

Inheritance diagram

static __await__() → object

__init__()

Initializes the future in the pending state.

static __iter__() → object

add_done_callback(fn: object) → object

cancel() → bool

Cancels the future. Returns true if it was cancelled, or false if the future was already done. Either way, done() will return true after this call returns.

Please note that calling this is not a guarantee that the operation corresponding this future does not run. It could already be in the process of running, or perhaps not respond to a cancel signal. All this guarantees is that the future is marked as done when this call returns.

In the case of a task, this is equivalent to remove().

cancelled() → bool

Returns true if the future was cancelled. It is always safe to call this.

done() → bool

Returns true if the future is done or has been cancelled. It is always safe to call this.

property done_event → string

Getter

Returns the event name that will be triggered when the future finishes. See set_done_event().

Setter

Sets the event name that will be triggered when the future finishes. Will not be triggered if the future is cancelled, but it will be triggered for a coroutine task that exits with an exception.

static gather(args: object) → object

static get_class_type() → TypeHandle

get_done_event() → str

Returns the event name that will be triggered when the future finishes. See set_done_event().

output(out: ostream)

result(timeout: object) → object

set_done_event(done_event: str)

Sets the event name that will be triggered when the future finishes. Will not be triggered if the future is cancelled, but it will be triggered for a coroutine task that exits with an exception.

set_result(param0: object)

static shield(future: AsyncFuture) → AsyncFuture

Creates a new future that shields the given future from cancellation. Calling cancel() on the returned future will not affect the given future.

wait()

Waits until the future is done.

wait(timeout: float)

Waits until the future is done, or until the timeout is reached. Note that this can be considerably less efficient than wait() without a timeout, so it’s generally not a good idea to use this unless you really need to.