issues: 776520994

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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
776520994 MDU6SXNzdWU3NzY1MjA5OTQ= 4741 Attribute style access is slow 32801740 closed 0     2 2020-12-30T15:52:07Z 2021-01-05T23:00:29Z 2021-01-05T23:00:29Z CONTRIBUTOR      

I appreciate xarray's ability to use attribute style access ds.foo as an alternative to ds["foo"] as it requires less characters/keystrokes and has less 'visual clutter'.

A drawback is that it can be much slower as lookup time seems to display O(n) behaviour instead of O(1) with n being the number of variables in the dataset. For e.g. n=100 it is approximately 100 times slower than dictionary-style access:

# Dataset with many (100) variables
ds = xr.Dataset({f'var{v}': [] for v in range(100)})

%timeit ds['var0']
462 µs ± 1.5 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)

%timeit ds.var0
47.1 ms ± 205 µs per loop (mean ± std. dev. of 7 runs, 10 loops each)

dir() and _ipython_key_completions_() which are used for e.g. tab completion in iPython are equally slow:

%timeit dir(ds)
47 ms ± 163 µs per loop (mean ± std. dev. of 7 runs, 10 loops each)

%timeit ds._ipython_key_completions_()
46.8 ms ± 210 µs per loop (mean ± std. dev. of 7 runs, 10 loops each)

I would like to see xarray having much better performance for attribute style access.

 
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