See if type meta object is an instance of another class Question: I’m wondering if there’s a way of seeing whether a class is inherited from another class based on the type object for a given object. Say I have the class MyList as defined below: class MyList(list): pass Now consider the following: >>> my_list …
How Meta classes works in python? Question: Origin of question I’m recently working with django and became used to of Meta class in models, Serializers, and Forms. My Understanding so far I learned that meta classes are used for creating classes. When one class is defined, Python will go inside the class and collect all …
How to register classes that inherit from an abstract class in python Question: I’m creating a module with a function that works as a factory of the implemented classes. It works registering the classes with the help of a metaclass (a pattern I have just copied from here). _registry = {} def register_class(cls): _registry[cls.__name__] = …
Using metaclass to keep track of instances in python Question: I need to keep tracks of instances of some classes (and do other stuff with those classes). I would like to not have to declare any extra code in the classes in question, thus everything should ideally be handled in the metaclass. What I can’t …
How to use my own Meta class together with SQLAlchemy-Model as a parent class Question: I recently started to use Flask as my back-end framework. However, recently I encountered a problem and I could not figure out how to solve it. As a last resort I wanted to try my change here. If you could …
Python – What does it mean for a Class to be callable? Question: I am trying to understand what ‘callables’ are in Python and what it means for a class to be callable. I was playing with the following code: class A(object): def __init__(self): pass print(“Is A callable? ” + str(callable(A))) a=A() print(“created a”) a() …
Understanding __init_subclass__ Question: I finally upgraded my python version and I was discovering the new features added. Among other things, I was scratching my head around the new __init_subclass__ method. From the docs: This method is called whenever the containing class is subclassed. cls is then the new subclass. If defined as a normal instance …
How to determine the metaclass of a class? Question: I have a class object, cls. I want to know its metaclass. How do I do this? (If I wanted to know its parent classes, I would do cls.__mro__. Is there something like this to get the metaclass?) Asked By: Pro Q || Source Answers: Ok …
When should I subclass EnumMeta instead of Enum? Question: In this article Nick Coghlan talks about some of the design decisions that went in to the PEP 435 Enum type, and how EnumMeta can be subclassed to provide a different Enum experience. However, the advice I give (and I am the primary stdlib Enum author) …
python subclasscheck & subclasshook Question: The methods __subclasscheck__ and __subclasshook__ are used to determine if a class is regarded as subclass of another. However, their documentation is very limited, even in advanced Python books. How are they meant to be used and what is their difference (higher priority, side of relationship they refer to etc…)? …
