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POPolymorphism with callables in Python
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9459580
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CreationDate
2012-02-27T03:11:21.280
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1
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2012-02-29T12:57:06.943
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2012-02-27T07:55:13.703
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1
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2
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text
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I have an interface class called iResource, and a number of subclasses, each of which implement the "request" method. The request functions use socket I/O to other machines, so it makes sense to run them asynchronously, so those other machines can work in parallel. The problem is that when I start a thread with iResource.request and give it a subclass as the first argument, it'll call the superclass method. If I try to start it with "type(a).request" and "a" as the first argument, I get "" for the value of type(a). Any ideas what that means and how to get the true type of the method? Can I formally declare an abstract method in Python somehow? EDIT: Including code. <pre><code>def getSocialResults(self, query=''): #for a in self.types["social"]: print type(a) tasks = [type(a).request for a in self.types["social"]] argss = [(a, query, 0) for a in self.types["social"]] grabbers = executeChainResults(tasks, argss) return igrabber.cycleGrabber(grabbers) </code></pre> "executeChainResults" takes a list "tasks" of callables and a list "argss" of args-tuples, and assumes each returns a list. It then executes each in a separate thread, and concatenates the lists of results. I can post that code if necessary, but I haven't had any problems with it so I'll leave it out for now. The objects "a" are DEFINITELY not of type iResource, since it has a single constructor that just throws an exception. However, replacing "type(a).request" with "iResource.request" invokes the base class method. Furthermore, calling "self.types["social"][0].request" directly works fine, but the above code gives me: "type object 'instance' has no attribute 'request'". Uncommenting the commented line prints <code><type 'instance'></code> several times.
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<python><instance><callable>
Title
Polymorphism with callables in Python
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