Parent is a class – blue print not an instance of it, in OOPS to access attributes of an object it requires instance of the same, Here self/child is instance while Parent/Child are classes… see the answer below, may clarify your doubts. class Parent(): def __init__(self): self.myvar = 1 class Child(Parent): def __init__(self): Parent.__init__(self) # … Read more
Well sure! Let’s assume that you have in interface IMyCollection. It has a method boolean isMutable(). Now you have two classes, class MyMutableList and class MyImmutableList, which both implement IMyCollection. Each of them would override the instance method isMutable(), with MyMutableList simply returning true and MyImmutableList returning false. isMutable() in both classes is an instance … Read more
It depends if you want a pointer or not. It’s better to call your structure like this : typedef struct s_data { int a; char *b; // etc.. } t_data; After to instanciate it for a no-pointer structure : t_data my_struct; my_struct.a = 8; And if you want a pointer you need to malloc it … Read more
One way to keep track of instances is with a class variable: class A(object): instances = [] def __init__(self, foo): self.foo = foo A.instances.append(self) At the end of the program, you can create your dict like this: foo_vars = {id(instance): instance.foo for instance in A.instances} There is only one list: >>> a = A(1) >>> … Read more
From here, a static call is 4 to 5 times faster than constructing an instance every time you call an instance method. However, we’re still only talking about tens of nanoseconds per call, so you’re unlikely to notice any benefit unless you have really tight loops calling a method millions of times, and you could … Read more
To understand the “display class” you have to understand closures. The lambda you pass here is a closure, a special type of method that magically drags in state from the scope of the method it’s in and “closes around” it. …except of course that there’s no such thing as magic. All that state has to … Read more
As Jon first suggested, you can try creating a mutex. Call CreateMutex. If you get a non-null handle back, then call GetLastError. It will tell you whether you were the one who created the mutex or whether the mutex was already open before (Error_Already_Exists). Note that it is not necessary to acquire ownership of the … Read more
The singleton scope When a bean is a singleton, only one shared instance of the bean will be managed, and all requests for beans with an id or ids matching that bean definition will result in that one specific bean instance being returned by the Spring container. To put it another way, when you define … Read more
inspect.ismethod is what you want to find out if you definitely have a method, rather than just something you can call. import inspect def foo(): pass class Test(object): def method(self): pass print inspect.ismethod(foo) # False print inspect.ismethod(Test) # False print inspect.ismethod(Test.method) # True print inspect.ismethod(Test().method) # True print callable(foo) # True print callable(Test) # True … Read more
This is because of the way Python resolves names with the .. When you write self.list the Python runtime tries to resolve the list name first by looking for it in the instance object, and if it is not found there, then in the class instance. Let’s look into it step by step self.list.append(1) Is … Read more