Update xarray/core/dataset.py

Author: hmaarrfk

xarray/core/dataset.py

@@ -2994,8 +2994,7 @@ def isel(
                 # without any relevant dimensions for slicing.
                 # Pick those out quickly and avoid paying the cost below
                 # of resolving the var_indexers variables
-                var_indexer_keys = all_keys.intersection(var_dims)
-                if var_indexer_keys:
+                if var_indexer_keys := all_keys.intersection(var_dims):
                     var_indexers = {k: indexers[k] for k in var_indexer_keys}
                     var = var.isel(var_indexers)
                     if drop and var.ndim == 0 and name in coord_names: