Tlis wrote: > I am using a software system with an embedded Python interpreter > (version 2.3) for scripting. The KcsPoint2D.py module contains a > Point2D class with the following method: > > def SetFromMidpoint(self, p1, p2): > if not isinstance(p1, Point2D) or not isinstance(p2, Point2D): > raise TypeError, 'some error message' > --- > > The problem is that after I launch my script once, and then use the > 'Reload modules' button (presumably it calls reload() on all loaded > modules), the isinstance() tests shown above fails, even though the > expressions: > > type(self) > type(p1) > type(p2) > > all show: class 'KcsPoint2D.Point2D' > > Could you explain, please what is going on? Why the isinstance() > function returns False?
You just discovered one reason why reload() is a bad idea and IMHO shouldn't be used at all - as tempting it might be. Reload will re-execute the importing of the module and perform all necessary initializations there, overwrite names in the module namespace and such. But it _won't_ magically change classes or other objects being referred to from other code that have been created prior to the reloading. Consider this example: class A(object): foo = 10 a = A() class A(object): foo = 20 print a.foo >>> 10 All that happens is that the name A is bound to a new class. So all subsequent instantiations are of the new type. But not the old instances - because the refer to their class not by NAME, but just have a pointer to it. Diez -- http://mail.python.org/mailman/listinfo/python-list
