Enforce ruff/Pylint Convention rules (PLC) (#10460)

* Apply ruff/Pylint rule PLC0105

PLC0105 `TypeVar` name does not reflect its covariance

* Apply ruff/Pylint rule PLC0206

PLC0206 Extracting value from dictionary without calling `.items()`

* Apply ruff/Pylint rule PLC1802

PLC1802 `len()` used as condition without comparison

* Ignore ruff/Pylint rule PLC2401

PLC2401 Variable name contains a non-ASCII character

* Enforce ruff/Pylint Convention rules (PLC)

Author: DimitriPapadopoulos

pyproject.toml

@@ -260,6 +260,7 @@ extend-select = [
   "PERF", # Perflint
   "W",    # pycodestyle warnings
   "PGH",  # pygrep-hooks
+  "PLC",  # Pylint Convention
   "PLE",  # Pylint Errors
   "PLR",  # Pylint Refactor
   "PLW",  # Pylint Warnings
@@ -278,6 +279,8 @@ ignore = [
   "PERF203", # try-except within a loop incurs performance overhead
   "E402",    # module level import not at top of file
   "E731",    # do not assign a lambda expression, use a def
+  "PLC0415", # `import` should be at the top-level of a file
+  "PLC0206", # extracting value from dictionary without calling `.items()`
   "PLR091",  # too many arguments / branches / statements
   "PLR2004", # magic value used in comparison
   "PLW0603", # using the global statement to update is discouraged

xarray/core/types.py

@@ -195,7 +195,7 @@ def copy(
 
 # Temporary placeholder for indicating an array api compliant type.
 # hopefully in the future we can narrow this down more:
-T_DuckArray = TypeVar("T_DuckArray", bound=Any, covariant=True)
+T_DuckArray = TypeVar("T_DuckArray", bound=Any, covariant=True)  # noqa: PLC0105
 
 # For typing pandas extension arrays.
 T_ExtensionArray = TypeVar("T_ExtensionArray", bound=pd.api.extensions.ExtensionArray)

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
     )

xarray/tests/test_dataset.py

@@ -1214,7 +1214,7 @@ def test_chunk_by_frequency(self, freq: str, calendar: str, add_gap: bool) -> No
         import dask.array
 
         N = 365 * 2
-        ΔN = 28
+        ΔN = 28  # noqa: PLC2401
         time = xr.date_range(
             "2001-01-01", periods=N + ΔN, freq="D", calendar=calendar
         ).to_numpy(copy=True)

xarray/tests/test_groupby.py

@@ -1321,8 +1321,7 @@ def test_groupby_properties(self) -> None:
         grouped = self.da.groupby("abc")
         expected_groups = {"a": range(9), "c": [9], "b": range(10, 20)}
         assert expected_groups.keys() == grouped.groups.keys()
-        for key in expected_groups:
-            expected_group = expected_groups[key]
+        for key, expected_group in expected_groups.items():
             actual_group = grouped.groups[key]
 
             # TODO: array_api doesn't allow slice:

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):