metaclass Questions

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I would like to have in the code underneath that when i type instance_of_A = A(, that the name of the supposed arguments is init_argumentA and not *meta_args, **meta_kwargs. But unfortunatally, the...
Excise asked 9/4, 2018 at 19:28

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I am writing unit tests for an MCU that communicates commands through the USB port and checks their response. If one unit test fails it makes sense for me to do some debugging in the MCU. Therefore...
Catalano asked 8/5, 2015 at 10:3

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I would like to create a new Enum (IntEnum) class based on two existing ones. There is a working solution for this, like so: from enum import unique, IntEnum from itertools import chain from colle...
Carycaryatid asked 6/9, 2017 at 10:56

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This question is not for the discussion of whether or not the singleton design pattern is desirable, is an anti-pattern, or for any religious wars, but to discuss how this pattern is best implement...
Pap asked 20/7, 2011 at 10:47

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I would like to create a class which defines a particular interface, and then require all subclasses to conform to this interface. For example, I would like to define a class class Interface: def...
Lodged asked 23/3, 2019 at 1:35

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I'm doing some distributed computing in which several machines communicate under the assumption that they all have identical versions of various classes. Thus, it seems to be good design to make th...
G asked 14/2, 2011 at 20:16

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I've got some code that uses a metaclass in python. But when sphinx autodoc is run it is giving the error: WARNING: py:class reference target not found: type The error is occuring in a line of an...
Midyear asked 10/7, 2012 at 15:55

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I am teaching myself about the __prepare__ function. And I see this snippet at PEP3115 # The custom dictionary class member_table(dict): def __init__(self): self.member_names = [] def __setite...
Bibliography asked 19/10, 2017 at 10:21

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What are metaclasses? What are they used for?
Braden asked 19/9, 2008 at 6:10

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What can be done with metaclasses that can't be in any other way? Alex Martelli told that there are tasks that can't be achieved without metaclasses here Python metaclasses vs class decorators I'd...
Airbrush asked 5/1, 2010 at 12:12

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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 y...
Bolivia asked 30/4, 2019 at 16:34

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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 ide...
Missive asked 7/7, 2019 at 1:25

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I need to simulate enums in Python, and did it by writing classes like: class Spam(Enum): k = 3 EGGS = 0 HAM = 1 BAKEDBEANS = 2 Now I'd like to test if some constant is a valid choice for a ...
Sher asked 4/5, 2012 at 9:1

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I'm using argspec in a function that takes another function or method as the argument, and returns a tuple like this: (("arg1", obj1), ("arg2", obj2), ...) This means that the first argument to ...
Wu asked 31/5, 2011 at 9:21

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I would like to know if it's possible to control the context automatically in a metaclass and decorator. I have written a decorator function that creates the stub from the grpc insecure channel: de...
Hengist asked 22/6, 2022 at 6:34

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As an example, consider the following: class FooMeta(type): def __len__(cls): return 9000 class GoodBar(metaclass=FooMeta): def __len__(self): return 9001 class BadBar(metaclass=FooMeta): ...
Susan asked 17/5, 2022 at 20:4

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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 custo...
Teal asked 6/8, 2011 at 12:28

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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 metho...
Dune asked 30/7, 2017 at 13:25

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I would like to define metaclass that will enable me to create properties (i.e. setter, getter) in new class on the base of the class's attributes. For example, I would like to define the class: ...
Calamity asked 24/12, 2014 at 0:23

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I have a friend who likes to use metaclasses, and regularly offers them as a solution. I am of the mind that you almost never need to use metaclasses. Why? because I figure if you are doing someth...
Elagabalus asked 24/12, 2008 at 20:13

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I have a class that need to make some magic with every operator, like __add__, __sub__ and so on. Instead of creating each function in the class, I have a metaclass which defines every operator in...
Umbelliferous asked 26/12, 2011 at 16:2

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I created a metaclass that defines the __prepare__ method, which is supposed to consume a specific keyword in the class definition, like this: class M(type): @classmethod def __prepare__(metaclas...
Insouciant asked 8/10, 2021 at 9:4

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I need a double inheritance for a class that is an Enum but also support my own methods. Here's the context: import abc from enum import Enum class MyFirstClass(abc.ABC): @abc.abstractmethod def...
Derogative asked 31/8, 2021 at 20:35

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Consider the following metaclass/class definitions: class Meta(type): """A python metaclass.""" def greet_user(cls): """Print a friendly greeting ide...
Slattery asked 22/8, 2021 at 16:7

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When defining an abstract metaclass in python and instantiating it like this: from abc import ABC, abstractmethod class AbstractMetaClass(type, ABC): @abstractmethod def func(self): pass cla...
Orelia asked 25/6, 2021 at 17:55

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