Apply ruff/Pylint rule PLC1802

PLC1802 `len()` used as condition without comparison
pydata · dcherian · Jun 28, 2025 · Jun 28, 2025 · Jun 28, 2025 · Jun 28, 2025
commit 138a2a4d85cecbc051da9570367af84d8336ed61
diff --git a/xarray/tests/test_dask.py b/xarray/tests/test_dask.py
@@ -1372,7 +1372,7 @@ def test_map_blocks_da_ds_with_template(obj):
 
     # Check that indexes are written into the graph directly
     dsk = dict(actual.__dask_graph__())
-    assert len({k for k in dsk if "x-coordinate" in k})
+    assert {k for k in dsk if "x-coordinate" in k}
     assert all(
         isinstance(v, PandasIndex) for k, v in dsk.items() if "x-coordinate" in k
     )

diff --git a/xarray/ufuncs.py b/xarray/ufuncs.py
@@ -39,7 +39,7 @@ def get_array_namespace(*args):
         names = [module.__name__ for module in xps]
         raise ValueError(f"Mixed array types {names} are not supported.")
 
-    return next(iter(xps)) if len(xps) else np
+    return next(iter(xps)) if xps else np
 
 
 class _ufunc_wrapper(ABC):