Thanks for the note, Nick. I ended up with cycles as a historical reason. Some code that were written long time ago did not anticipate that part of it will get sub-classed.
Thanks again. Nick Vatamaniuc wrote: > John, > Cycles are tricky. Python is an interpreted dynamic language, whatever > object you instantiate in your methods is a different thing than class > hierarchy. Your class hierarchy is fine: ClassA->ClassASubclass->ClassC > and it should work. If it doesn't, create a quick mock example and > post it along with the error. > > In general try to model your problem to avoid cycles if possible, I > know sometimes they are un-avoidable, but more often then not, they > are. Python might or might not allow cycles in certain situations > (packages, imports, class hierarchy and during usage i.e. in your > semantics) but regardless, if they make your code hard to understand so > try to not introduce them if possible. > > Hope this helps, > Nick V. > > > John Henry wrote: > > Hi list, > > > > I am trying to understand better Python packaging. This might be a > > messed up class hierachy but how would I break this cyclic relatioship? > > > > In file A: > > > > from B import B_Class > > > > Class_A_Main(): > > def .... > > def SomeMethod(self): > > res=B_Class(self) > > > > Class_A_SubClass(Class_A_Main): > > def ... > > > > > > In file B: > > > > Class B_Class(): > > def __init__(self,parent): > > ... > > def SomeMethod(self): > > res=C_Class(self) > > > > > > In file C: > > > > from file A import Class_A_SubClass > > > > Class C_Class(Class_A_SubClass): > > def __init__(self, parent): > > ... > > > > > > As you can see, the cyclic relationship exists because C_Class is a > > sub-class of SubClass which is in turn a sub-class of Class_A_Main and > > in one of the methods of Class_A, it has a need to create a C_Class > > object. > > > > I tried to merge the files A and C (by placing C_Class behind A_Class) > > and have the method in A_Class create C_Class directly but that doesn't > > work because Python says C_Class is not defined when it's processing > > the A_Class method. May be somebody can tell me how to "forward > > declare" a class? > > > > Regards, -- http://mail.python.org/mailman/listinfo/python-list
