twisted.internet.defer

Schedule the execution of a coroutine that awaits/yields from Deferreds, wrapping it in a Deferred that will fire on success/failure of the coroutine. If a Deferred is passed to this function, it will be returned directly (mimicking the asyncio.ensure_future function).

See Deferred.fromCoroutine for examples of coroutines.

Create a Deferred from a callable and arguments.

Call the given function with the given arguments. Return a Deferred which has been fired with its callback as the result of that invocation or its errback with a Failure for the exception thrown.

Return a Deferred that has already had .errback(result) called.

See succeed's docstring for rationale.

Returns, via a Deferred, a list with the results of the given Deferreds - in effect, a "join" of multiple deferred operations.

The returned Deferred will fire when all of the provided Deferreds have fired, or when any one of them has failed.

This method can be cancelled by calling the cancel method of the Deferred, all the Deferreds in the list will be cancelled.

This differs from DeferredList in that you don't need to parse the result for success/failure.

Determine whether Deferred debugging is enabled.

inlineCallbacks helps you write Deferred-using code that looks like a regular sequential function. For example:

    @inlineCallbacks
    def thingummy():
        thing = yield makeSomeRequestResultingInDeferred()
        print(thing)  # the result! hoorj!

When you call anything that results in a Deferred, you can simply yield it; your generator will automatically be resumed when the Deferred's result is available. The generator will be sent the result of the Deferred with the 'send' method on generators, or if the result was a failure, 'throw'.

Things that are not Deferreds may also be yielded, and your generator will be resumed with the same object sent back. This means yield performs an operation roughly equivalent to maybeDeferred.

Your inlineCallbacks-enabled generator will return a Deferred object, which will result in the return value of the generator (or will fail with a failure object if your generator raises an unhandled exception). Inside the generator simply use return result to return a value.

Be aware that generator must not return a Deferred. If you believe the thing you'd like to return could be a Deferred, do this:

    result = yield result
    return result

The Deferred returned from your deferred generator may errback if your generator raised an exception:

    @inlineCallbacks
    def thingummy():
        thing = yield makeSomeRequestResultingInDeferred()
        if thing == 'I love Twisted':
            # will become the result of the Deferred
            return 'TWISTED IS GREAT!'
        else:
            # will trigger an errback
            raise Exception('DESTROY ALL LIFE')

You can cancel the Deferred returned from your inlineCallbacks generator before it is fired by your generator completing (either by reaching its end, a return statement, or by calling returnValue). A CancelledError will be raised from the yielded Deferred that has been cancelled if that Deferred does not otherwise suppress it.

inlineCallbacks behaves very similarly to coroutines. Since Twisted 24.7.0 it is possible to rewrite functions using inlineCallbacks to async def in piecewise manner and be mostly compatible to existing code.

The rewrite process is simply replacing inlineCallbacks decorator with async def and all yield occurrences in the function body with await. The function will no longer return a Deferred but a awaitable coroutine. This return value will obviously not have Deferred methods such as addCallback, but it will be possible to yield it in other code based on inlineCallbacks.

Log and return failure.

This method can be used as an errback that passes the failure on to the next errback unmodified. Note that if this is the last errback, and the deferred gets garbage collected after being this errback has been called, the clean up code logs it again.

Invoke a function that may or may not return a Deferred or coroutine.

Call the given function with the given arguments. Then:

• If the returned object is a Deferred, return it.
• If the returned object is a Failure, wrap it with fail and return it.
• If the returned object is a types.CoroutineType, wrap it with Deferred.fromCoroutine and return it.
• Otherwise, wrap it in succeed and return it.
• If an exception is raised, convert it to a Failure, wrap it in fail, and then return it.

Undocumented

Select the first available result from the sequence of Deferreds and cancel the rest.

Return val from a inlineCallbacks generator.

Note: this is currently implemented by raising an exception derived from BaseException. You might want to change any 'except:' clauses to an 'except Exception:' clause so as not to catch this exception.

Also: while this function currently will work when called from within arbitrary functions called from within the generator, do not rely upon this behavior.

Enable or disable Deferred debugging.

When debugging is on, the call stacks from creation and invocation are recorded, and added to any AlreadyCalledErrors we raise.

Return a Deferred that has already had .callback(result) called.

This is useful when you're writing synchronous code to an asynchronous interface: i.e., some code is calling you expecting a Deferred result, but you don't actually need to do anything asynchronous. Just return defer.succeed(theResult).

See fail for a version of this function that uses a failing Deferred rather than a successful one.

Undocumented