dict incorrectly being detected as "object"

[noisecapella]

I narrowed down the problem to this repro case:

LOGGING = {
    'handlers': {
    },
    'loggers': {
        'django': {
        },
        'django.request': {
        },
        'urllib3': {
        }
    },
}

LOGGING['handlers'].pop('syslog')

When I run mypy 0.4.2 on this file (named test.py) I get this error:

test.py:14: error: "object" has no attribute "pop"

Thanks for your help!

[gvanrossum]

I'd add a type annotation to the LOGGING variable, something like # type: Dict[str, <whatever you want>].

Do note that mypy currently doesn't support different (fixed) keys of a dict having different types -- that's probably what's biting you. That and the empty dicts.

[noisecapella]

The type annotation addresses the warning I got. FYI I got another warning after adding the type annotation. Not sure if it's a known problem or not but adding it here in case it's helpful. Here is the updated input:

LOGGING = {
    'handlers': {
    },
    'loggers': {
        'django': {
        },
        'django.request': {
        },
        'urllib3': {
        }
    },
   }  # type: Dict[str, Dict[str, str]]

LOGGING['handlers'].pop('syslog')

Warning:

test.py:4: error: List item 0 has incompatible type "Tuple[str, Dict[None, None]]"
test.py:4: error: List item 1 has incompatible type "Tuple[str, Dict[None, None]]"
test.py:4: error: List item 2 has incompatible type "Tuple[str, Dict[None, None]]"

[rwbarton]

It looks like your LOGGING variable actually has a type like Dict[str, Dict[str, Dict[_, _]]] for some _s.

[noisecapella]

Yes you're right. When I update the type annotation accordingly it fixes the problem