issues: 957201551

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id node_id number title user state locked assignee milestone comments created_at updated_at closed_at author_association active_lock_reason draft pull_request body reactions performed_via_github_app state_reason repo type
957201551 MDU6SXNzdWU5NTcyMDE1NTE= 5655 Allow .attrs to use dict-likes 14371165 open 0     2 2021-07-31T08:31:55Z 2022-01-09T03:32:04Z   MEMBER      

Is your feature request related to a problem? Please describe. Reading attributes from h5py-files is rather slow. So instead of retrieving it immediately I wanted to create a lazy dict-class that only retrieves the attribute values when necessary. But this is difficult to achieve since xarray keeps forcing the attrs to dicts in a lot of places.

Describe the solution you'd like * Replace in https://github.com/pydata/xarray/blob/dddac11b01330791ffab4dfc72d226e71821973e/xarray/core/variable.py#L865 and https://github.com/pydata/xarray/blob/dddac11b01330791ffab4dfc72d226e71821973e/xarray/core/dataset.py#L798 with a asdict(value) function that checks if the input is a valid dict-like, if not convert to dict. Things that might be good to check: * MutableMapping * hasattr(dict_like, "copy") * isinstance(dict_like, dict) == True * Remove unneccessary conversions to dict. For example https://github.com/pydata/xarray/blob/dddac11b01330791ffab4dfc72d226e71821973e/xarray/core/merge.py#L523 should not be necessary as attrs from variables/dataarrays/datasets have already been forced to dicts when they were initialized.

Describe alternatives you've considered * One could lazify with dicts as well, for example by replacing the value with a function. This however won't look good in reprs, that's why having a convienence class is nice. * dict(LazyDict) always forces to dict, it does not let it pass through unchanged even if isinstance(LazyDict, dict) == True.

Interesting reading: https://stackoverflow.com/questions/16669367/setup-dictionary-lazily https://stackoverflow.com/questions/3387691/how-to-perfectly-override-a-dict

 
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