[Question] What is an alternative to isinstance(obj, QuerySet)?

[martin-thoma]

I've recently got

Parameterized generics cannot be used with class or instance checks

with django-stubs==1.9.0 for isinstance(obj, QuerySet) when I run mypy over the code.

What is the recommended way to do it?

[sobolevn]

This is because QuerySet is now = _QuerySet[_T, _T] from cfd69c0#diff-389fe7d7dcfb77ddaac87c1f3bdc196f3ef0ca33b8047c6638a15f3a3db21b56R170

We can try to alias it as QuerySet = _QuerySet it should be the same thing, but without subscription.

@MT-Cash can you please try that?

[martin-thoma]

From where should I import _QuerySet?

[sobolevn]

You cannot import _QuerySet, because it is our only-in-stubs thing. You can send a Pr with the [_T, _T] removed from this line: cfd69c0#diff-389fe7d7dcfb77ddaac87c1f3bdc196f3ef0ca33b8047c6638a15f3a3db21b56R170

It might help.

[jerch]

Kinda stumbled over the same issue and can confirm, that removing [_T, _T] solved it for me.

Created PR #794.