AssertionError: yield from wasn't used with future The stack trace looks like: main function encountered error Traceback most recent call last : File "b. AssertionError: yield from wasn't used with future I think the asyncio. I advise you to ask on the Twisted mailing list to get more detailed feedback.
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Featured on Meta. New post summary designs on greatest hits now, everywhere else eventually. Related 6. Hot Network Questions. Question feed. If True , registration will be done, otherwise it will not be. This should happen in the during startup event trigger phase. I add reader to the set of file descriptors to get read events for. Parameters reader An IReadDescriptor provider that will be checked for read events until it is removed from the reactor with removeReader.
I add writer to the set of file descriptors to get write events for. Parameters writer An IWriteDescriptor provider that will be checked for write events until it is removed from the reactor with removeWriter. Remove all readers and writers. Should not remove reactor internal reactor connections like a waker. Return the list of file descriptors currently monitored for input events by the reactor. Returns the list of file descriptors monitored for input events.
Return the list file descriptors currently monitored for output events by the reactor. Returns the list of file descriptors monitored for output events. See twisted. Connects a given DatagramProtocol to the given path.
Connects a ConnectedDatagramProtocol instance to a path. Create a new IListeningPort from an already-initialized socket. Extend the base implementation in order to remember whether signal handlers should be installed later. A flag which indicates whether any signal handlers will be installed during startup.
Extend the base implementation by also installing signal handlers, if self. See IReactorCore. A flag which is true between paired calls to reactor. A flag which is true from the time reactor. Your program might use the simplest of all possible models, in which it actually sits and waits for data to be sent and received, but in this case it has some very obvious and basic limitations: it can't send many emails at once; and in fact it can't do anything else while it is sending an email.
Hence, all but the simplest network programs avoid this model. You can use one of several different models to allow your program to keep doing whatever tasks it has on hand while it is waiting for something to happen before a particular task can continue.
When dealing with many connections in one thread, the scheduling is the responsibility of the application, not the operating system, and is usually implemented by calling a registered function when each connection is ready to for reading or writing -- commonly known as asynchronous , event-driven or callback-based programming.
What advantage does the above sequence have over our original blocking sequence? The advantage is that while the email sending function can't do the next part of its job until the connection is open, the rest of the program can do other tasks, like begin the opening sequence for other email connections.
Hence, the entire program is not waiting for the connection. The typical asynchronous model for alerting an application that some data is ready for it is known as a callback.
The application calls a function to request some data, and in this call, it also passes a callback function that should be called when the data is ready with the data as an argument.
The callback function should therefore perform whatever tasks it was that the application needed that data for. In synchonous programming, a function requests data, waits for the data, and then processes it.
In asynchronous programming, a function requests the data, and lets the library call the callback function when the data is ready. Twisted uses the Deferred object to manage the callback sequence. The client application attaches a series of functions to the deferred to be called in order when the results of the asychronous request are available this series of functions is known as a series of callbacks , or a callback chain , together with a series of functions to be called if there is an error in the asychronous request known as a series of errbacks or an errback chain.
The asychronous library code calls the first callback when the result is available, or the first errback when an error occurs, and the Deferred object then hands the results of each callback or errback function to the next function in the chain. It is the second class of concurrency problem — non-computationally intensive tasks that involve an appreciable delay — that Deferreds are designed to help solve.
Functions that wait on hard drive access, database access, and network access all fall into this class, although the time delay varies. Deferreds are designed to enable Twisted programs to wait for data without hanging until that data arrives. They do this by giving a simple management interface for callbacks to libraries and applications. Libraries know that they always make their results available by calling Deferred. Applications set up result handlers by attaching callbacks and errbacks to deferreds in the order they want them called.
The basic idea behind Deferreds, and other solutions to this problem, is to keep the CPU as active as possible. If one task is waiting on data, rather than have the CPU and the program!
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