From: Of Ben Elliston Sent: Wednesday, September 28, 2016 6:40 AM To: code-quality@python.org Subject: [code-quality] false positive for unidiomatic-typecheck?

I am seeing the following message from pylint:

foo.py:311: [C0123(unidiomatic-typecheck), _legend] Using type() instead

of

isinstance() for a typecheck.

My line is: if type(g) not in unique:

Do note that this is the same as if isinstance(g, tuple(unique)):

Since isinstance() accepts either a type or a tuple or types (not a set, list, or any other iterable, though).

That is, I am maintaing a list of unique types in a set of objects. This isn't a typecheck. Shouldn't the warning only be produced when type(x) is compared with type(y)?

Actually, that is a typecheck; it's just not one you're used to seeing. You're checking for the presence of the type of 'g' in a set. Using `type(x)` is often unidiomatic, and in almost every case (including this one), you have a better alternative :)

Thanks, Ben

-Emanuel