how to declare type for defaultdict(defaultdict)

[matt-the-midnight-hacker]

Hi I just updated pyright to 1.1.377 and I get now type errors for defaultdict(defaultdict) assignments. I'm not sure if it is a bug or a typeshed issue or just me.

The code to reproduce what I mean would be:

from typing import DefaultDict
from collections import defaultdict

class MyClass:
    pass

d: DefaultDict[int, DefaultDict[int, MyClass]] = defaultdict(defaultdict)

d[1][2] = MyClass()

I get error:

error: Expression of type "defaultdict[Unknown, defaultdict[Unknown, defaultdict[Unknown, Unknown]]]" is incompatible with declared type "DefaultDict[int, DefaultDict[int, MyClass]]

How to do the defaultdict instantiation here to fulfill the type I've declared?

fyi. I've also asked this on stackoverflow

[erictraut]

On first inspection, this looks like a bug. I'll create an issue from the discussion. In the meantime, you can work around the issue this way:

d: DefaultDict[int, DefaultDict[int, MyClass]] = defaultdict(defaultdict[int, MyClass])

This workaround might not work on older versions of Python where defaultdict was not indexable.

[erictraut]

Here's the issue: #8840.

[matt-the-midnight-hacker]

thank you so much

[tofetpuzo]

wish I could take up this challenge 😉 .