Dataclasses and slots causing ValueError: 'b' in __slots__ conflicts with class variable Question: I don’t understand the error message and also couldn’t find other SO questions and answers helping me to understand this. The MWE is tested with Python 3.9.2. I’m aware that there is a slots=True parameter in Pythons 3.10 dataclasses. But this isn’t …
Store an array, or a list, of fixed length as a class attribute using slots in python Question: I have an object that represents a User and a variable measured 20 times. The object will be something like this: class User: user_id: str measures: List[float] #this is a list(or an array) of size 20 Given …
Are Python 3.11 objects as light as slots? Question: After Mark Shannon’s optimisation of Python objects, is a plain object different from an object with slots? I understand that after this optimisation in a normal use case, the objects have no dictionary. Have the new Python objects made it unnecessary to use slots at all? …
TypeError when calling super() in dataclass(slots=True) subclass Question: I am trying to call a a superclass method from a dataclass with slots=True in Python 3.10.5. from dataclasses import dataclass @dataclass(slots=True) class Base: def hi(self): print("Hi") @dataclass(slots=True) class Sub(Base): def hi(self): super().hi() Sub().hi() I get the following error. Traceback (most recent call last): File "…", line …
Using __setattr__ and __getattr__ for delegation with __slots__ without triggering infinite recursion Question: class A: __slots__ = ("a",) def __init__(self) -> None: self.a = 1 class B1: __slots__ = ("b",) def __init__(self, b) -> None: self.b = b def __getattr__(self, k): return getattr(self.b, k) def __setattr__(self, k, v): setattr(self.b, k, v) class B2: __slots__ = …
How can dataclasses be made to work better with __slots__? Question: It was decided to remove direct support for __slots__ from dataclasses for Python 3.7. Despite this, __slots__ can still be used with dataclasses: from dataclasses import dataclass @dataclass class C(): __slots__ = "x" x: int However, because of the way __slots__ works it isn’t …
Why am I getting an error about my class defining __slots__ when trying to pickle an object? Question: I’m trying to pickle an object of a (new-style) class I defined. But I’m getting the following error: >>> with open(‘temp/connection.pickle’,’w’) as f: … pickle.dump(c,f) … Traceback (most recent call last): File “<stdin>”, line 2, in <module> …
How does inheritance of __slots__ in subclasses actually work? Question: In the Python data model reference section on slots there is a list of notes on using __slots__. I am thoroughly confused by the 1st and 6th items, because they seem to be contradicting each other. First item: When inheriting from a class without __slots__, …
Usage of __slots__? Question: What is the purpose of __slots__ in Python — especially with respect to when I would want to use it, and when not? Asked By: Jeb || Source Answers: You would want to use __slots__ if you are going to instantiate a lot (hundreds, thousands) of objects of the same class. …
