I am a little bit confused about the object and type classes in Python 3. Maybe someone can clear up my confusion or provide some additional information. My current understanding is that every class (except object) inherits from a base class called object. But every class (including object) is also an instanc…
Tag: oop
Instance error in OOP design: Instance of Card has No points member
I’m reading this book called Master Object Oriented programming Python by Steven Lott. I came across this code: I’m not able to understand how can self._points() in Card be legal expression. I run the code in compiler too it stats the following error Instance of Card has No points member Full Code…
Terminology: A user-defined function object attribute?
According to Python 2.7.12 documentation, User-defined methods: User-defined method objects may be created when getting an attribute of a class (perhaps via an instance of that class), if that attribute is a user-defined function object, an unbound user-defined method object, or a class method object. When th…
Python circular imports with inheritance
I have a parent and child class, where a parent’s method returns an instance of the child. Both classes are in separate files classA.py and classB.py. In order to avoid circular imports when I import classA I added the classB import to the end of classA.py (as shown below). Everything worked well and I …
How to copy all attributes of one Python object to another?
I’ve got two classes, of which one inherits from the other: I now create a Parent and change the attributes: And from this point, I want to create a Child in which I want to copy all the attributes from the parent. I can of course do this like so: The thing is that while developing, this class will grow
Override a “private” method in Python
Consider a class with a “private” method such as: When I try to subclass Foo and override method __method, it can be seen that Foo.__method is still called, instead of MoreFoo.__method. What would be the way to override such a method? Answer The point of using the double-underscore name convention…
Using the __call__ method of a metaclass instead of __new__?
When discussing metaclasses, the docs state: You can of course also override other class methods (or add new methods); for example defining a custom __call__() method in the metaclass allows custom behavior when the class is called, e.g. not always creating a new instance. [Editor’s note: This was remov…
Is there a benefit to defining a class inside another class in Python?
What I’m talking about here are nested classes. Essentially, I have two classes that I’m modeling. A DownloadManager class and a DownloadThread class. The obvious OOP concept here is composition. However, composition doesn’t necessarily mean nesting, right? I have code that looks something l…