On Thu, Nov 11, 2021 at 10:06:45PM -0500, Ricky Teachey wrote:
Is there a standard idiom-- perhaps using a type-hint-- to signal to the IDE/linter that my user-defined class is intended to be used as a function/factory, and not as a type (even though it is in fact a type)?
Not really. I don't think there is even a standard idiom for the human reader to decide whether something is used as a "function" or a "class". It is subjective, based on usage and convention. As others have pointed out, many functions in Python can be considered as class constructor: ord(number) # constructs a string even traditional functional programming, er, functions like map: map(func, iterable) # returns a map object I think that the best I can come up with is that if your class has a constructor that attaches input arguments (with or without additional processing) as attributes, then it might be considered "class-like". Something like this: class C: def __new__(cls, arg): obj = super().__new__(cls) obj.attribute = arg return obj or equivalently: class C: def __init__(self, arg): self.attribute = arg But if it looks like more this: class C: def __new__(cls, arg): obj = _convert(arg) # possibly call a dunder method? return obj then it is probably "function-like". But honestly, it's subjective. Some things feel like a transformation, conversion or cast using a function, and some things feel like constructing an object, even if it is impossible to find a hard, objective, bullet-proof distinction.
Seems like if there were a standard idiom for telling the linter "this class is really just kind of a factory, don't complain about the lowercase", it might be kind of nice.
Any decent linter should have a switch to turn off a specific check for a line of code. For example, in flake8 the error code for class names is N801, so you should be able to disable that using: # noqa: N801 https://flake8.pycqa.org/en/3.1.1/user/ignoring-errors.html https://github.com/PyCQA/pep8-naming -- Steve