Properties expose fields. Fields should (almost always) be kept private to a class and accessed via get and set properties. Properties provide a level of abstraction allowing you to change the fields while not affecting the external way they are accessed by the things that use your class. public class MyClass { // this is … Read more
To summarize the contents of other (already good!) answers, isinstance caters for inheritance (an instance of a derived class is an instance of a base class, too), while checking for equality of type does not (it demands identity of types and rejects instances of subtypes, AKA subclasses). Normally, in Python, you want your code to … Read more
How about an analogy: when I was in the Air Force, I went to pilot training and became a USAF (US Air Force) pilot. At that point I wasn’t qualified to fly anything, and had to attend aircraft type training. Once I qualified, I was a pilot (Abstract class) and a C-141 pilot (concrete class). … Read more
Is there any reason for a class declaration to inherit from object? In Python 3, apart from compatibility between Python 2 and 3, no reason. In Python 2, many reasons. Python 2.x story: In Python 2.x (from 2.2 onwards) there’s two styles of classes depending on the presence or absence of object as a base-class: … Read more
There are some good answers here. I would add to them the following points. What is the correct C# way of representing a data structure, which, “logically” (that is to say, “to the human mind”) is just a list of things with a few bells and whistles? Ask any ten non-computer-programmer people who are familiar … Read more
Single Underscore In a class, names with a leading underscore indicate to other programmers that the attribute or method is intended to be be used inside that class. However, privacy is not enforced in any way. Using leading underscores for functions in a module indicates it should not be imported from somewhere else. From the … Read more
An abstract function cannot have functionality. You’re basically saying, any child class MUST give their own version of this method, however it’s too general to even try to implement in the parent class. A virtual function, is basically saying look, here’s the functionality that may or may not be good enough for the child class. … Read more
There are actually many good reasons to consider using accessors rather than directly exposing fields of a class – beyond just the argument of encapsulation and making future changes easier. Here are the some of the reasons I am aware of: Encapsulation of behavior associated with getting or setting the property – this allows additional … Read more
Though classmethod and staticmethod are quite similar, there’s a slight difference in usage for both entities: classmethod must have a reference to a class object as the first parameter, whereas staticmethod can have no parameters at all. Example class Date(object): def __init__(self, day=0, month=0, year=0): self.day = day self.month = month self.year = year @classmethod … Read more
Prefer composition over inheritance as it is more malleable / easy to modify later, but do not use a compose-always approach. With composition, it’s easy to change behavior on the fly with Dependency Injection / Setters. Inheritance is more rigid as most languages do not allow you to derive from more than one type. So … Read more