It’s a bit longer than what you started with, but this does what you asked for… and a little more besides – for example, callMethod(receiver, “voidMethod”) where voidMethod takes no arguments also works. static void callMethod(Object receiver, String methodName, Object… params) { if (receiver == null || methodName == null) { return; } Class<?> cls … Read more
Python’s scoping rules for barenames are very simple and straightforward: local namespace first, then (if any) outer functions in which the current one is nested, then globals, finally built-ins. That’s all that ever happens when a barename is looked up, and there’s no need to memorize or apply any complicated rules (nor is there any … Read more
Firstly, I recommend you follow Björn Pollex’s advice (+1). To get past this particular problem (type(l2 + l3) == CustomList), you need to implement a custom __add__(): def __add__(self, rhs): return CustomList(list.__add__(self, rhs)) And for extended slicing: def __getitem__(self, item): result = list.__getitem__(self, item) try: return CustomList(result) except TypeError: return result I also recommend… pydoc … Read more
Reclassing instances like this is done in Mercurial (a distributed revision control system) when extensions (plugins) want to change the object that represent the local repository. The object is called repo and is initially a localrepo instance. It is passed to each extension in turn and, when needed, extensions will define a new class which … Read more
In order to understand this, it’s probably important to understand the way an object is stored during runtime. There is a class object1, which holds all the method implementations, and separately, there is a structure with the storage for the instance’s variables. All instances of a class share the one class object. When you call … Read more
As float is immutable you have to overwrite __new__ as well. The following should do what you want: class Foo(float): def __new__(self, value, extra): return float.__new__(self, value) def __init__(self, value, extra): float.__init__(value) self.extra = extra foo = Foo(1,2) print(str(foo)) 1.0 print(str(foo.extra)) 2 See also Sub-classing float type in Python, fails to catch exception in __init__()
If you want to access properties of a subclass, you’re going to have to cast to the subclass. if (g instanceof Sphere) { Sphere s = (Sphere) g; System.out.println(s.radius); …. } This isn’t the most OO way to do things, though: once you have more subclasses of Geometry you’re going to need to start casting … Read more
PEP 487 sets out to take two common metaclass usecases and make them more accessible without having to understand all the ins and outs of metaclasses. The two new features, __init_subclass__ and __set_name__ are otherwise independent, they don’t rely on one another. __init_subclass__ is just a hook method. You can use it for anything you … Read more
Are you looking for: Super.class.isAssignableFrom(Sub.class)
Rounding up Ignacio’s answer and orokusaki’s comment you probably should write something like import turtle class TurtleGTX(turtle.Turtle): “””My own version of turtle””” def __init__(self,*args,**kwargs): super(TurtleGTX,self).__init__(*args,**kwargs) print(“Time for my GTX turtle!”) my_turtle = TurtleGTX() my_turtle.forward(100)