Python event driven framwork
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Publisher.evt_foo event should be published when foo method runs, and the code corresponds to this is self.evt_foo(). They are used when user do help(Publisher). Aregument of event.Event contains document about the event itself. You can easily know what kind of events this class publishes with this way. Now events are members of the class (not of instance). You will find that the event-related codes are written more declaratively and naturally there: Usageīefore event.py, Let’s look at the sample script code which uses it. Here’s the implementation that avoids the matters above. Is it impossible unless revising the specifications of Python? Well, no, it is possible think how they implement the Python's property mechanism. Imagine defining events of a class as just like a methods or properties of that. However, it is not recommended that forcing subclassing upon them. that is called EventPublisher) with a mechanism that fires event, and ask users to subclass it. However, this approach needs codes like self.evt_foo = eventEvent(self) in _init_, so only moves points of the problem.Īnother approach: you design a class (e.g.
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You may pass the sender objects of the events in _init_, to fire events like self.evt_foo().
PYTHON EVENT DRIVEN FRAMWORK HOW TO
How about that? If you are sure that they understand what event mechanism is and how to use our module, that’s totally OK. See Python document about these special methods.Ī script which uses this module will be like this: The last 3-line-code enables you to write your code like e += handler, e -= handler and e(earg) instead of e.add(handler), e.remove(handler) and e.fire(earg). Let's start with a simple implementation: I, however, don't have much time to do that now.) Simpler implementation (TODO: Maybe I should explain the C#’s event mechanism and show how wonderful it is. This article shows yet another implementation of event mechanism in Python, which is a little bit improved by using an interesting feature of Python, descriptor. You can find a lot of event implementations in Python too see search results for “c# event python” in Google for instance. Some people implement the same mechanism in their favorite languages other than C#. This is quite simply not true.The event mechanism in C# is nice. For applications that need true concurrency, Twisted provides alternatives, such as Ampoule.īecause people tend to hear "don't use threads, use Twisted" within one minute of each other, people mistakenly assume that writing programs asynchronously means that things can't be evaluated in parallel. For most applications that Twisted is a good idea for, that's not really a big problem. Yes, most Twisted applications don't do computational concurrency. In fact, it's one of the more problematic ones. Many people say "threading" when they mean "concurrency", but here is a key difference: Threading isn't the only concurrency model by far. Twisted lets you write them in a single thread, which makes debugging much less of a pain.īut all new processors have billions of cores, single threaded apps are terrible?! For networking apps, threading is still the predominant implementation. Two typical examples of these are:Įveryone writing GUI apps (like PyQt) is already writing asynchronously, even if they cheat by using threads. If you can't find what you need in the Twisted API docs, try one of the following:Īn asynchronous event loop is generally useful, but particularly well suited to applications that spend most of their time waiting.
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Twisted supports a whole boatload of things, not necessarily limited to networking protocols. When you're writing Twisted-powered applications, you typically won't be doing that. However, if you've written a GUI, you've probably sidestepped that event loop by having your application run in a separate thread. Most GUIs use an event loop, just like Twisted.
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If you've ever used a GUI toolkit, you probably have, though. It's a different to how you're used to writing things. Twisted is a framework for writing asynchronous applications in Python. Twisted, an event-driven networking engine for Python