What’s the difference? SomeBaseClass.__init__(self) means to call SomeBaseClass‘s __init__. while super().__init__() means to call a bound __init__ from the parent class that follows SomeBaseClass‘s child class (the one that defines this method) in the instance’s Method Resolution Order (MRO). If the instance is a subclass of this child class, there may be a different parent … Read more
The first is used to initialise newly created object, and receives arguments used to do that: class Foo: def __init__(self, a, b, c): # … x = Foo(1, 2, 3) # __init__ The second implements function call operator. class Foo: def __call__(self, a, b, c): # … x = Foo() x(1, 2, 3) # __call__
I’ll take the risk of stating the obvious: You call the function, if it’s defined in the base class it’s automatically available in the derived class (unless it’s private). If there is a function with the same signature in the derived class you can disambiguate it by adding the base class’s name followed by two … Read more
Use the super() function: class Foo(Bar): def baz(self, **kwargs): return super().baz(**kwargs) For Python < 3, you must explicitly opt in to using new-style classes and use: class Foo(Bar): def baz(self, arg): return super(Foo, self).baz(arg)
In Python, there is a difference between functions and bound methods. >>> def foo(): … print “foo” … >>> class A: … def bar( self ): … print “bar” … >>> a = A() >>> foo <function foo at 0x00A98D70> >>> a.bar <bound method A.bar of <__main__.A instance at 0x00A9BC88>> >>> Bound methods have been … Read more
Let’s take your example of a Dog and a Cat class, and let’s illustrate using C#: Both a dog and a cat are animals, specifically, quadruped mammals (animals are waaay too general). Let us assume that you have an abstract class Mammal, for both of them: public abstract class Mammal This base class will probably … Read more
When do you choose functional programming over object oriented? When you anticipate a different kind of software evolution: Object-oriented languages are good when you have a fixed set of operations on things, and as your code evolves, you primarily add new things. This can be accomplished by adding new classes which implement existing methods, and … Read more
UPDATE: This question was the subject of an immensely long blog series, which you can read at Monads — thanks for the great question! In terms that an OOP programmer would understand (without any functional programming background), what is a monad? A monad is an “amplifier” of types that obeys certain rules and which has … Read more
There are some wonderful answers on here to this questions that get into all sorts of great detail about interfaces and loosely coupling code, inversion of control and so on. There are some fairly heady discussions, so I’d like to take the opportunity to break things down a bit for understanding why an interface is … Read more
In this code: class A(object): def __init__(self): self.x = ‘Hello’ def method_a(self, foo): print self.x + ‘ ‘ + foo … the self variable represents the instance of the object itself. Most object-oriented languages pass this as a hidden parameter to the methods defined on an object; Python does not. You have to declare it … Read more