mypy question

[Thomas Passin]

On 12/30/2023 9:14 AM, Thomas Passin via Python-list wrote:
> On 12/29/2023 10:02 AM, Karsten Hilbert via Python-list wrote:
>> I agree that mypy's grasp of my intent from
>>
>>     queries:list[dict[str, str | list | dict[str, Any]]]=None,
>>
>> into
>>
>>     "List[Dict[str, Union[str, List[Any], Dict[str, Any]]]]"
>>
>> seems accurate. I just don't understand why list[dict[str,
>> str]] should not pass that construct.
> 
> I made a tiny test program with your type signature, and got this error 
> message from mypy:
> 
> c:\temp\python\typing_test.py:3: error: X | Y syntax for unions requires 
> Python 3.10  [syntax]
> 
> Aside from that, this variation causes no mypy error (you must use 
> Sequence instead of List), and is also more clear about what you are 
> trying to get:
> 
> from typing import Union, Sequence, Dict
> 
> DictType1 = Dict[str, str]
> DictType2 = Dict[str, Sequence]
> DictType3 = Dict[str, Dict]
> QueryType = Sequence[Union[DictType1, DictType2, DictType3]]
> 
> def test_typing(queries:QueryType=None):
>      print(type(queries))
> 
> d1 = {'k1': 'v1', 'k2': 'v2'}
> queries = [d1,]
> test_typing(queries)
> 
> I'm not sure if this captures exactly what you want, but it avoids the 
> problem where mypy does not regard str and Union[str, list] as 
> equivalent types.  I tested this using Python 3.12.

In doing more testing, I have learned that my suggestion above does 
work, *except* that you cannot mix-and-match different DictTypex types 
within the same Sequence - meaning within the same query argument.  Any 
of the Union types is OK but they all have to be the same in any instance.