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
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