On 10/20/2010 11:49 PM, Zachary Pincus wrote:
Hi Robert, so in a big data analysis framework, that is essentially written in C ++, exposed to python with SWIG, plus dedicated python modules, the user performs an analysis choosing some given modules by name,as in : myOpt="foo" my_analyse.perform(use_optimizer=myOpt)
The attribute use_optimizer is then checked to perform the right calls/instantiations of python but also C++ objects..... and the actual crunching number is in the C++ part. But then I realize that I need to tweak this optimizer's state, and the optimizer object is accessible from a library pyOpt that has been swigified from a C++ library. Then I access the object by calling optObject = eval("pyOpt.%s(some_args)"%myOpt) where myOpt would be "foo" in this particular analysis. This is because what the attribute use_optimizer expects is also the object name in the library, of course. It goes without saying that I could do : if myOpt=="foo": optObject=pyOpt.foo(some_args) else: .... and if you guys tell me it is way safer, I will do that instead of the use of eval that I liked because of the compactness.....
Well, optObject=getattr(pyOpt, myOpt) is a bit nicer and marginally more likely to return sane error messages than optObject=eval("pyOpt. %s"%myOpt). Then you could do result=optObject(some_args)...
ok I definitely like that better than eval.
But why not have the user just pass in the relevant optObject from the pyOpt namespace (or some restricted namespace that just has the relevant functions exposed)? E.g. my_analysis.perform(optimizer=pyOpt.Amoeba) rather than my_analysis.perform(optimizer='Amoeba')
Well, that means that the user now needs to know about the underlying C++ library, etc.... Just requiring from the user that he knows the *name* of the optimizer was the primary driver. But I understand that it easily drives to a dead-end. my_analysis.perform(optimizer=pyOpt.Amoeba) is definitely allowed in the code as well, and that is what I do after I have fiddle with the optimizer object. Thanks to all for the tips and advices! Johann
This lets users do introspection on the pyOpt namespace to see what functions they can choose from, which is rather friendlier in an interactive environment.
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