diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 0233955d77..7c95eeaca3 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -29,7 +29,7 @@ repos:
     -   id: no-commit-to-branch
 
 -   repo: https://github.com/psf/black
-    rev: 22.12.0
+    rev: 23.1.0
     hooks:
     -   id: black
         pass_filenames: false
diff --git a/docs/gallery_code/general/plot_lineplot_with_legend.py b/docs/gallery_code/general/plot_lineplot_with_legend.py
index 78401817ba..aad7906acd 100644
--- a/docs/gallery_code/general/plot_lineplot_with_legend.py
+++ b/docs/gallery_code/general/plot_lineplot_with_legend.py
@@ -24,7 +24,6 @@ def main():
     )
 
     for cube in temperature.slices("longitude"):
-
         # Create a string label to identify this cube (i.e. latitude: value).
         cube_label = "latitude: %s" % cube.coord("latitude").points[0]
 
diff --git a/docs/gallery_code/general/plot_projections_and_annotations.py b/docs/gallery_code/general/plot_projections_and_annotations.py
index 75122591b9..2cf42e66e0 100644
--- a/docs/gallery_code/general/plot_projections_and_annotations.py
+++ b/docs/gallery_code/general/plot_projections_and_annotations.py
@@ -26,7 +26,6 @@
 
 
 def make_plot(projection_name, projection_crs):
-
     # Create a matplotlib Figure.
     plt.figure()
 
diff --git a/docs/gallery_code/general/plot_zonal_means.py b/docs/gallery_code/general/plot_zonal_means.py
index 08a9578e63..195f8b4bb0 100644
--- a/docs/gallery_code/general/plot_zonal_means.py
+++ b/docs/gallery_code/general/plot_zonal_means.py
@@ -16,7 +16,6 @@
 
 
 def main():
-
     # Loads air_temp.pp and "collapses" longitude into a single, average value.
     fname = iris.sample_data_path("air_temp.pp")
     temperature = iris.load_cube(fname)
diff --git a/docs/gallery_code/meteorology/plot_lagged_ensemble.py b/docs/gallery_code/meteorology/plot_lagged_ensemble.py
index 5cd2752f39..e15aa0e6ef 100644
--- a/docs/gallery_code/meteorology/plot_lagged_ensemble.py
+++ b/docs/gallery_code/meteorology/plot_lagged_ensemble.py
@@ -86,7 +86,6 @@ def main():
 
     # Iterate over all possible latitude longitude slices.
     for cube in last_timestep.slices(["latitude", "longitude"]):
-
         # Get the ensemble member number from the ensemble coordinate.
         ens_member = cube.coord("realization").points[0]
 
diff --git a/docs/src/userguide/plotting_examples/1d_with_legend.py b/docs/src/userguide/plotting_examples/1d_with_legend.py
index 9b9fd8a49d..626335af45 100644
--- a/docs/src/userguide/plotting_examples/1d_with_legend.py
+++ b/docs/src/userguide/plotting_examples/1d_with_legend.py
@@ -13,7 +13,6 @@
 temperature = temperature[5:9, :]
 
 for cube in temperature.slices("longitude"):
-
     # Create a string label to identify this cube (i.e. latitude: value)
     cube_label = "latitude: %s" % cube.coord("latitude").points[0]
 
diff --git a/lib/iris/__init__.py b/lib/iris/__init__.py
index 896b850541..a81d25add3 100644
--- a/lib/iris/__init__.py
+++ b/lib/iris/__init__.py
@@ -175,7 +175,6 @@ def __init__(self, datum_support=False, pandas_ndim=False):
         self.__dict__["pandas_ndim"] = pandas_ndim
 
     def __repr__(self):
-
         # msg = ('Future(example_future_flag={})')
         # return msg.format(self.example_future_flag)
         msg = "Future(datum_support={}, pandas_ndim={})"
diff --git a/lib/iris/_merge.py b/lib/iris/_merge.py
index bc12080523..5ca5f31a8e 100644
--- a/lib/iris/_merge.py
+++ b/lib/iris/_merge.py
@@ -1418,6 +1418,7 @@ def _define_space(self, space, positions, indexes, function_matrix):
             participates in a functional relationship.
 
         """
+
         # Heuristic reordering of coordinate defintion indexes into
         # preferred dimension order.
         def axis_and_name(name):
diff --git a/lib/iris/analysis/__init__.py b/lib/iris/analysis/__init__.py
index 55d5d5d93e..f34cda1402 100644
--- a/lib/iris/analysis/__init__.py
+++ b/lib/iris/analysis/__init__.py
@@ -296,7 +296,6 @@ def _dimensional_metadata_comparison(*cubes, object_get=None):
     # for coordinate groups
     for cube, coords in zip(cubes, all_coords):
         for coord in coords:
-
             # if this coordinate has already been processed, then continue on
             # to the next one
             if id(coord) in processed_coords:
diff --git a/lib/iris/analysis/_area_weighted.py b/lib/iris/analysis/_area_weighted.py
index edbfd41ef9..3b728e9a43 100644
--- a/lib/iris/analysis/_area_weighted.py
+++ b/lib/iris/analysis/_area_weighted.py
@@ -853,7 +853,7 @@ def _calculate_regrid_area_weighted_weights(
         cached_x_bounds = []
         cached_x_indices = []
         max_x_indices = 0
-        for (x_0, x_1) in grid_x_bounds:
+        for x_0, x_1 in grid_x_bounds:
             if grid_x_decreasing:
                 x_0, x_1 = x_1, x_0
             x_bounds, x_indices = _cropped_bounds(src_x_bounds, x_0, x_1)
diff --git a/lib/iris/analysis/_interpolation.py b/lib/iris/analysis/_interpolation.py
index 2a7dfa6e62..f5e89a9e51 100644
--- a/lib/iris/analysis/_interpolation.py
+++ b/lib/iris/analysis/_interpolation.py
@@ -268,7 +268,7 @@ def _account_for_circular(self, points, data):
         """
         from iris.analysis.cartography import wrap_lons
 
-        for (circular, modulus, index, dim, offset) in self._circulars:
+        for circular, modulus, index, dim, offset in self._circulars:
             if modulus:
                 # Map all the requested values into the range of the source
                 # data (centred over the centre of the source data to allow
diff --git a/lib/iris/analysis/_scipy_interpolate.py b/lib/iris/analysis/_scipy_interpolate.py
index fc64249729..bfa070c7c7 100644
--- a/lib/iris/analysis/_scipy_interpolate.py
+++ b/lib/iris/analysis/_scipy_interpolate.py
@@ -225,7 +225,6 @@ def compute_interp_weights(self, xi, method=None):
         prepared = (xi_shape, method) + self._find_indices(xi.T)
 
         if method == "linear":
-
             xi_shape, method, indices, norm_distances, out_of_bounds = prepared
 
             # Allocate arrays for describing the sparse matrix.
diff --git a/lib/iris/analysis/calculus.py b/lib/iris/analysis/calculus.py
index c530dbd216..75b7d86406 100644
--- a/lib/iris/analysis/calculus.py
+++ b/lib/iris/analysis/calculus.py
@@ -594,7 +594,6 @@ def curl(i_cube, j_cube, k_cube=None):
         horiz_cs, (iris.coord_systems.GeogCS, iris.coord_systems.RotatedGeogCS)
     )
     if not spherical_coords:
-
         # TODO Implement some mechanism for conforming to a common grid
         dj_dx = _curl_differentiate(j_cube, x_coord)
         prototype_diff = dj_dx
diff --git a/lib/iris/analysis/trajectory.py b/lib/iris/analysis/trajectory.py
index c21d71d48c..24f7a9dede 100644
--- a/lib/iris/analysis/trajectory.py
+++ b/lib/iris/analysis/trajectory.py
@@ -85,7 +85,6 @@ def __init__(self, waypoints, sample_count=10):
         cur_seg = segments[cur_seg_i]
         len_accum = cur_seg.length
         for p in range(self.sample_count):
-
             # calculate the sample position along our total length
             sample_at_len = p * sample_step
 
diff --git a/lib/iris/common/metadata.py b/lib/iris/common/metadata.py
index 8ec39bb4b1..cb3149fe58 100644
--- a/lib/iris/common/metadata.py
+++ b/lib/iris/common/metadata.py
@@ -969,6 +969,7 @@ def _combine_lenient(self, other):
             A list of combined metadata member values.
 
         """
+
         # Perform "strict" combination for "coord_system" and "climatological".
         def func(field):
             left = getattr(self, field)
@@ -1024,6 +1025,7 @@ def _difference_lenient(self, other):
             A list of difference metadata member values.
 
         """
+
         # Perform "strict" difference for "coord_system" and "climatological".
         def func(field):
             left = getattr(self, field)
diff --git a/lib/iris/coord_categorisation.py b/lib/iris/coord_categorisation.py
index 72019b4b87..698b4828f1 100644
--- a/lib/iris/coord_categorisation.py
+++ b/lib/iris/coord_categorisation.py
@@ -90,6 +90,7 @@ def vectorised_fn(*args):
 # coordinates only
 #
 
+
 # Private "helper" function
 def _pt_date(coord, time):
     """
diff --git a/lib/iris/coord_systems.py b/lib/iris/coord_systems.py
index 802571925e..edf0c1871b 100644
--- a/lib/iris/coord_systems.py
+++ b/lib/iris/coord_systems.py
@@ -478,7 +478,6 @@ def datum(self, value):
 
     @classmethod
     def from_datum(cls, datum, longitude_of_prime_meridian=None):
-
         crs = super().__new__(cls)
 
         crs._semi_major_axis = None
@@ -949,7 +948,6 @@ def __init__(
         false_northing=None,
         ellipsoid=None,
     ):
-
         """
         Constructs a Geostationary coord system.
 
diff --git a/lib/iris/coords.py b/lib/iris/coords.py
index cfcdcd92a0..91bb786ae8 100644
--- a/lib/iris/coords.py
+++ b/lib/iris/coords.py
@@ -2846,7 +2846,6 @@ def _new_bounds_requirements(self, bounds):
             n_bounds = bounds.shape[-1]
             n_points = bounds.shape[0]
             if n_points > 1:
-
                 directions = set()
                 for b_index in range(n_bounds):
                     monotonic, direction = iris.util.monotonic(
diff --git a/lib/iris/cube.py b/lib/iris/cube.py
index c60896f718..abe37c35fb 100644
--- a/lib/iris/cube.py
+++ b/lib/iris/cube.py
@@ -2688,7 +2688,6 @@ def subset(self, coord):
             coord_to_extract in self.aux_coords
             and len(coord_to_extract.points) == 1
         ):
-
             # Default to returning None
             result = None
 
diff --git a/lib/iris/experimental/ugrid/mesh.py b/lib/iris/experimental/ugrid/mesh.py
index d18e1b2026..0d566da73f 100644
--- a/lib/iris/experimental/ugrid/mesh.py
+++ b/lib/iris/experimental/ugrid/mesh.py
@@ -3127,9 +3127,7 @@ def _construct_access_arrays(self):
             flat_inds_safe = al.where(missing_inds, 0, flat_inds_nomask)
             # Here's the core indexing operation.
             # The comma applies all inds-array values to the *first* dimension.
-            bounds = node_points[
-                flat_inds_safe,
-            ]
+            bounds = node_points[flat_inds_safe,]
             # Fix 'missing' locations, and restore the proper shape.
             bounds = al.ma.masked_array(bounds, missing_inds)
             bounds = bounds.reshape(indices.shape)
diff --git a/lib/iris/experimental/ugrid/metadata.py b/lib/iris/experimental/ugrid/metadata.py
index ae0b787908..44bbe04fe9 100644
--- a/lib/iris/experimental/ugrid/metadata.py
+++ b/lib/iris/experimental/ugrid/metadata.py
@@ -53,6 +53,7 @@ def _combine_lenient(self, other):
             A list of combined metadata member values.
 
         """
+
         # Perform "strict" combination for "cf_role", "start_index", "location_axis".
         def func(field):
             left = getattr(self, field)
@@ -113,6 +114,7 @@ def _difference_lenient(self, other):
             A list of difference metadata member values.
 
         """
+
         # Perform "strict" difference for "cf_role", "start_index", "location_axis".
         def func(field):
             left = getattr(self, field)
@@ -233,6 +235,7 @@ def _difference_lenient(self, other):
             A list of difference metadata member values.
 
         """
+
         # Perform "strict" difference for "topology_dimension",
         # "node_dimension", "edge_dimension" and "face_dimension".
         def func(field):
@@ -297,6 +300,7 @@ def _combine_lenient(self, other):
             A list of combined metadata member values.
 
         """
+
         # It is actually "strict" : return None except where members are equal.
         def func(field):
             left = getattr(self, field)
@@ -352,6 +356,7 @@ def _difference_lenient(self, other):
             A list of different metadata member values.
 
         """
+
         # Perform "strict" difference for location / axis.
         def func(field):
             left = getattr(self, field)
diff --git a/lib/iris/fileformats/abf.py b/lib/iris/fileformats/abf.py
index 5c70c5acf2..4dcd5ce6aa 100644
--- a/lib/iris/fileformats/abf.py
+++ b/lib/iris/fileformats/abf.py
@@ -219,7 +219,6 @@ def load_cubes(filespecs, callback=None):
 
     for filespec in filespecs:
         for filename in glob.glob(filespec):
-
             field = ABFField(filename)
             cube = field.to_cube()
 
diff --git a/lib/iris/fileformats/name_loaders.py b/lib/iris/fileformats/name_loaders.py
index d15a3717d0..b9b64a343e 100644
--- a/lib/iris/fileformats/name_loaders.py
+++ b/lib/iris/fileformats/name_loaders.py
@@ -994,7 +994,6 @@ def load_NAMEIII_version2(filename):
     # using the next() method. This will come in handy as we wish to
     # progress through the file line by line.
     with open(filename, "r") as file_handle:
-
         # define a dictionary to hold the header metadata about this file
         header = read_header(file_handle)
 
@@ -1005,7 +1004,6 @@ def load_NAMEIII_version2(filename):
         column_headings = {}
         datacol1 = header["Number of preliminary cols"]
         for line in file_handle:
-
             data = [col.strip() for col in line.split(",")][:-1]
 
             # If first column is not zero we have reached the end
diff --git a/lib/iris/fileformats/pp.py b/lib/iris/fileformats/pp.py
index bc35acb3b3..cff088cf89 100644
--- a/lib/iris/fileformats/pp.py
+++ b/lib/iris/fileformats/pp.py
@@ -625,7 +625,7 @@ def __getstate__(self):
     def __setstate__(self, state):
         # Because we have __slots__, this is needed to support Pickle.load()
         # (Use setattr, as there is no object dictionary.)
-        for (key, value) in state:
+        for key, value in state:
             setattr(self, key, value)
 
     def __eq__(self, other):
@@ -2029,10 +2029,8 @@ def pp_filter(field):
         res = True
         if field.stash not in _STASH_ALLOW:
             if pp_constraints.get("stash"):
-
                 res = False
                 for call_func in pp_constraints["stash"]:
-
                     if call_func(str(field.stash)):
                         res = True
                         break
diff --git a/lib/iris/fileformats/pp_load_rules.py b/lib/iris/fileformats/pp_load_rules.py
index ebccec47ee..11d03e978a 100644
--- a/lib/iris/fileformats/pp_load_rules.py
+++ b/lib/iris/fileformats/pp_load_rules.py
@@ -756,7 +756,6 @@ def date2year(t_in):
             )
         )
     ):
-
         coords_and_dims.append(
             _new_coord_and_dims(
                 do_vector,
diff --git a/lib/iris/fileformats/rules.py b/lib/iris/fileformats/rules.py
index 07ed5eb8ce..51940b7c4d 100644
--- a/lib/iris/fileformats/rules.py
+++ b/lib/iris/fileformats/rules.py
@@ -394,7 +394,7 @@ def _load_pairs_from_fields_and_filenames(
             yield (cube, field)
 
     regrid_cache = {}
-    for (cube, factories, field) in results_needing_reference:
+    for cube, factories, field in results_needing_reference:
         _resolve_factory_references(
             cube, factories, concrete_reference_targets, regrid_cache
         )
diff --git a/lib/iris/fileformats/um/_fast_load_structured_fields.py b/lib/iris/fileformats/um/_fast_load_structured_fields.py
index d193aa30ce..64b7f8e891 100644
--- a/lib/iris/fileformats/um/_fast_load_structured_fields.py
+++ b/lib/iris/fileformats/um/_fast_load_structured_fields.py
@@ -133,6 +133,7 @@ def element_arrays_and_dims(self):
 
     def _field_vector_element_arrays(self):
         """Define the field components used in the structure analysis."""
+
         # Define functions to make t1 and t2 values as date-time tuples.
         # These depend on header version (PPField2 has no seconds values).
         def t1_fn(fld):
diff --git a/lib/iris/quickplot.py b/lib/iris/quickplot.py
index 18ed2554a3..6006314265 100644
--- a/lib/iris/quickplot.py
+++ b/lib/iris/quickplot.py
@@ -45,7 +45,6 @@ def _title(cube_or_coord, with_units):
             or units.is_no_unit()
             or units == cf_units.Unit("1")
         ):
-
             if _use_symbol(units):
                 units = units.symbol
             elif units.is_time_reference():
diff --git a/lib/iris/tests/graphics/__init__.py b/lib/iris/tests/graphics/__init__.py
index a083de3934..544d989564 100755
--- a/lib/iris/tests/graphics/__init__.py
+++ b/lib/iris/tests/graphics/__init__.py
@@ -187,7 +187,6 @@ def check_graphic(test_id: str, results_dir: Union[str, Path]) -> None:
     try:
 
         def _create_missing(phash: str) -> None:
-
             output_path = test_output_dir / (test_id + ".png")
 
             print(f"Creating image file: {output_path}")
@@ -214,7 +213,6 @@ def _create_missing(phash: str) -> None:
         phash = get_phash(buffer)
 
         if test_id in repo:
-
             expected = hex_to_hash(repo[test_id])
 
             # Calculate hamming distance vector for the result hash.
diff --git a/lib/iris/tests/integration/test_Datums.py b/lib/iris/tests/integration/test_Datums.py
index 77b7f28249..6953534f2d 100755
--- a/lib/iris/tests/integration/test_Datums.py
+++ b/lib/iris/tests/integration/test_Datums.py
@@ -23,7 +23,6 @@ def setUp(self):
         self.start_crs = ccrs.OSGB(False)
 
     def test_transform_points_datum(self):
-
         # Iris version
         wgs84 = GeogCS.from_datum("WGS84")
         iris_cs = LambertConformal(
diff --git a/lib/iris/tests/test_cdm.py b/lib/iris/tests/test_cdm.py
index 0615dc39bf..8f2a9b474d 100644
--- a/lib/iris/tests/test_cdm.py
+++ b/lib/iris/tests/test_cdm.py
@@ -349,7 +349,6 @@ def test_similar_coord(self):
         )
 
     def test_cube_summary_cell_methods(self):
-
         cube = self.cube_2d.copy()
 
         # Create a list of values used to create cell methods
diff --git a/lib/iris/tests/test_cf.py b/lib/iris/tests/test_cf.py
index 034fb1dbda..bf3cddb8b7 100644
--- a/lib/iris/tests/test_cf.py
+++ b/lib/iris/tests/test_cf.py
@@ -276,9 +276,7 @@ def test_destructor(self):
         didn't exist because opening the dataset had failed.
         """
         with self.temp_filename(suffix=".nc") as fn:
-
             with open(fn, "wb+") as fh:
-
                 fh.write(
                     b"\x89HDF\r\n\x1a\nBroken file with correct signature"
                 )
diff --git a/lib/iris/tests/test_io_init.py b/lib/iris/tests/test_io_init.py
index d33b76ddeb..82da82cfa9 100644
--- a/lib/iris/tests/test_io_init.py
+++ b/lib/iris/tests/test_io_init.py
@@ -126,7 +126,7 @@ def test_format_picker(self):
         ]
 
         # test that each filespec is identified as the expected format
-        for (expected_format_name, file_spec) in test_specs:
+        for expected_format_name, file_spec in test_specs:
             test_path = tests.get_data_path(file_spec)
             with open(test_path, "rb") as test_file:
                 a = iff.FORMAT_AGENT.get_spec(test_path, test_file)
diff --git a/lib/iris/tests/test_merge.py b/lib/iris/tests/test_merge.py
index c209d68da0..e53bbfb5f3 100644
--- a/lib/iris/tests/test_merge.py
+++ b/lib/iris/tests/test_merge.py
@@ -190,7 +190,7 @@ def setUp(self):
         )
 
     def test__ndarray_ndarray(self):
-        for (lazy0, lazy1) in self.lazy_combos:
+        for lazy0, lazy1 in self.lazy_combos:
             cubes = iris.cube.CubeList()
             cubes.append(self._make_cube(0, dtype=self.dtype, lazy=lazy0))
             cubes.append(self._make_cube(1, dtype=self.dtype, lazy=lazy1))
diff --git a/lib/iris/tests/test_netcdf.py b/lib/iris/tests/test_netcdf.py
index 5017698a22..92e15a414a 100644
--- a/lib/iris/tests/test_netcdf.py
+++ b/lib/iris/tests/test_netcdf.py
@@ -313,9 +313,7 @@ def test_deferred_loading(self):
             cube[((0, 8, 4, 2, 14, 12),)][((0, 2, 4, 1),)],
             ("netcdf", "netcdf_deferred_tuple_1.cml"),
         )
-        subcube = cube[((0, 8, 4, 2, 14, 12),)][((0, 2, 4, 1),)][
-            (1, 3),
-        ]
+        subcube = cube[((0, 8, 4, 2, 14, 12),)][((0, 2, 4, 1),)][(1, 3),]
         self.assertCML(subcube, ("netcdf", "netcdf_deferred_tuple_2.cml"))
 
         # Consecutive mixture on same dimension.
@@ -1417,7 +1415,6 @@ def test_process_flags(self):
         }
 
         for bits, descriptions in multiple_map.items():
-
             ll_cube = stock.lat_lon_cube()
             ll_cube.attributes["ukmo__process_flags"] = descriptions
 
diff --git a/lib/iris/tests/test_nimrod.py b/lib/iris/tests/test_nimrod.py
index a1d7bb298f..6d62623198 100644
--- a/lib/iris/tests/test_nimrod.py
+++ b/lib/iris/tests/test_nimrod.py
@@ -80,7 +80,8 @@ def test_huge_field_load(self):
     @tests.skip_data
     def test_load_kwarg(self):
         """Tests that the handle_metadata_errors kwarg is effective by setting it to
-        False with a file with known incomplete meta-data (missing ellipsoid)."""
+        False with a file with known incomplete meta-data (missing ellipsoid).
+        """
         datafile = "u1096_ng_ek00_pressure_2km"
         with self.assertRaisesRegex(
             TranslationError,
diff --git a/lib/iris/tests/test_pp_stash.py b/lib/iris/tests/test_pp_stash.py
index b153aef0d4..42390ab2b3 100644
--- a/lib/iris/tests/test_pp_stash.py
+++ b/lib/iris/tests/test_pp_stash.py
@@ -86,7 +86,6 @@ def test_irregular_stash_str(self):
         )
 
     def test_illegal_stash_str_range(self):
-
         self.assertEqual(iris.fileformats.pp.STASH(0, 2, 3), "m??s02i003")
         self.assertNotEqual(iris.fileformats.pp.STASH(0, 2, 3), "m01s02i003")
 
@@ -124,7 +123,7 @@ def test_illegal_stash_format(self):
             ("m01s02003", (1, 2, 3)),
         )
 
-        for (test_value, reference) in test_values:
+        for test_value, reference in test_values:
             msg = "Expected STASH code .* {!r}".format(test_value)
             with self.assertRaisesRegex(ValueError, msg):
                 test_value == iris.fileformats.pp.STASH(*reference)
@@ -137,7 +136,7 @@ def test_illegal_stash_type(self):
             (["m01s02i003"], "m01s02i003"),
         )
 
-        for (test_value, reference) in test_values:
+        for test_value, reference in test_values:
             msg = "Expected STASH code .* {!r}".format(test_value)
             with self.assertRaisesRegex(TypeError, msg):
                 iris.fileformats.pp.STASH.from_msi(test_value) == reference
diff --git a/lib/iris/tests/test_util.py b/lib/iris/tests/test_util.py
index db182ae3f3..d8d5d73e95 100644
--- a/lib/iris/tests/test_util.py
+++ b/lib/iris/tests/test_util.py
@@ -161,7 +161,6 @@ def test_default_values(self):
         )
 
     def test_trim_string_with_no_spaces(self):
-
         clip_length = 200
         no_space_string = "a" * 500
 
diff --git a/lib/iris/tests/unit/analysis/cartography/test_gridcell_angles.py b/lib/iris/tests/unit/analysis/cartography/test_gridcell_angles.py
index 6b957baec6..810851362e 100644
--- a/lib/iris/tests/unit/analysis/cartography/test_gridcell_angles.py
+++ b/lib/iris/tests/unit/analysis/cartography/test_gridcell_angles.py
@@ -94,7 +94,6 @@ def _check_multiple_orientations_and_latitudes(
         atol_degrees=0.005,
         cellsize_degrees=1.0,
     ):
-
         cube = _2d_multicells_testcube(cellsize_degrees=cellsize_degrees)
 
         # Calculate gridcell angles at each point.
diff --git a/lib/iris/tests/unit/coords/test_AncillaryVariable.py b/lib/iris/tests/unit/coords/test_AncillaryVariable.py
index 75b6250449..e5fc8fd28a 100644
--- a/lib/iris/tests/unit/coords/test_AncillaryVariable.py
+++ b/lib/iris/tests/unit/coords/test_AncillaryVariable.py
@@ -68,7 +68,7 @@ def setUp(self):
         self.setupTestArrays(masked=True)
 
     def test_lazyness_and_dtype_combinations(self):
-        for (ancill_var, data_lazyness) in data_all_dtypes_and_lazynesses(
+        for ancill_var, data_lazyness in data_all_dtypes_and_lazynesses(
             self,
         ):
             data = ancill_var.core_data()
@@ -225,10 +225,9 @@ def test_dtypes(self):
         # floating dtype.
         # Check that dtypes remain the same in all cases, taking the dtypes
         # directly from the core data as we have no masking).
-        for (main_ancill_var, data_lazyness) in data_all_dtypes_and_lazynesses(
+        for main_ancill_var, data_lazyness in data_all_dtypes_and_lazynesses(
             self
         ):
-
             sub_ancill_var = main_ancill_var[:2, 1]
 
             ancill_var_dtype = main_ancill_var.dtype
@@ -250,10 +249,9 @@ def test_lazyness(self):
         # Index ancillary variables with real+lazy data, and either an int or
         # floating dtype.
         # Check that lazy data stays lazy and real stays real, in all cases.
-        for (main_ancill_var, data_lazyness) in data_all_dtypes_and_lazynesses(
+        for main_ancill_var, data_lazyness in data_all_dtypes_and_lazynesses(
             self
         ):
-
             sub_ancill_var = main_ancill_var[:2, 1]
 
             msg = (
@@ -277,10 +275,9 @@ def test_lazyness(self):
     def test_real_data_copies(self):
         # Index ancillary variables with real+lazy data.
         # In all cases, check that any real arrays are copied by the indexing.
-        for (main_ancill_var, data_lazyness) in data_all_dtypes_and_lazynesses(
+        for main_ancill_var, data_lazyness in data_all_dtypes_and_lazynesses(
             self
         ):
-
             sub_ancill_var = main_ancill_var[:2, 1]
 
             msg = (
@@ -308,10 +305,9 @@ def test_lazyness(self):
         # Copy ancillary variables with real+lazy data, and either an int or
         # floating dtype.
         # Check that lazy data stays lazy and real stays real, in all cases.
-        for (main_ancill_var, data_lazyness) in data_all_dtypes_and_lazynesses(
+        for main_ancill_var, data_lazyness in data_all_dtypes_and_lazynesses(
             self
         ):
-
             ancill_var_dtype = main_ancill_var.dtype
             copied_ancill_var = main_ancill_var.copy()
 
@@ -338,10 +334,9 @@ def test_lazyness(self):
     def test_realdata_copies(self):
         # Copy ancillary variables with real+lazy data.
         # In all cases, check that any real arrays are copies, not views.
-        for (main_ancill_var, data_lazyness) in data_all_dtypes_and_lazynesses(
+        for main_ancill_var, data_lazyness in data_all_dtypes_and_lazynesses(
             self
         ):
-
             copied_ancill_var = main_ancill_var.copy()
 
             msg = (
@@ -520,79 +515,79 @@ def _check(self, result_ancill_var, expected_data, lazyness):
             self.assertEqualLazyArraysAndDtypes(expected_data, data)
 
     def test_add(self):
-        for (ancill_var, orig_data, data_lazyness) in self.test_combinations:
+        for ancill_var, orig_data, data_lazyness in self.test_combinations:
             result = ancill_var + 10
             expected_data = orig_data + 10
             self._check(result, expected_data, data_lazyness)
 
     def test_add_inplace(self):
-        for (ancill_var, orig_data, data_lazyness) in self.test_combinations:
+        for ancill_var, orig_data, data_lazyness in self.test_combinations:
             ancill_var += 10
             expected_data = orig_data + 10
             self._check(ancill_var, expected_data, data_lazyness)
 
     def test_right_add(self):
-        for (ancill_var, orig_data, data_lazyness) in self.test_combinations:
+        for ancill_var, orig_data, data_lazyness in self.test_combinations:
             result = 10 + ancill_var
             expected_data = 10 + orig_data
             self._check(result, expected_data, data_lazyness)
 
     def test_subtract(self):
-        for (ancill_var, orig_data, data_lazyness) in self.test_combinations:
+        for ancill_var, orig_data, data_lazyness in self.test_combinations:
             result = ancill_var - 10
             expected_data = orig_data - 10
             self._check(result, expected_data, data_lazyness)
 
     def test_subtract_inplace(self):
-        for (ancill_var, orig_data, data_lazyness) in self.test_combinations:
+        for ancill_var, orig_data, data_lazyness in self.test_combinations:
             ancill_var -= 10
             expected_data = orig_data - 10
             self._check(ancill_var, expected_data, data_lazyness)
 
     def test_right_subtract(self):
-        for (ancill_var, orig_data, data_lazyness) in self.test_combinations:
+        for ancill_var, orig_data, data_lazyness in self.test_combinations:
             result = 10 - ancill_var
             expected_data = 10 - orig_data
             self._check(result, expected_data, data_lazyness)
 
     def test_multiply(self):
-        for (ancill_var, orig_data, data_lazyness) in self.test_combinations:
+        for ancill_var, orig_data, data_lazyness in self.test_combinations:
             result = ancill_var * 10
             expected_data = orig_data * 10
             self._check(result, expected_data, data_lazyness)
 
     def test_multiply_inplace(self):
-        for (ancill_var, orig_data, data_lazyness) in self.test_combinations:
+        for ancill_var, orig_data, data_lazyness in self.test_combinations:
             ancill_var *= 10
             expected_data = orig_data * 10
             self._check(ancill_var, expected_data, data_lazyness)
 
     def test_right_multiply(self):
-        for (ancill_var, orig_data, data_lazyness) in self.test_combinations:
+        for ancill_var, orig_data, data_lazyness in self.test_combinations:
             result = 10 * ancill_var
             expected_data = 10 * orig_data
             self._check(result, expected_data, data_lazyness)
 
     def test_divide(self):
-        for (ancill_var, orig_data, data_lazyness) in self.test_combinations:
+        for ancill_var, orig_data, data_lazyness in self.test_combinations:
             result = ancill_var / 10
             expected_data = orig_data / 10
             self._check(result, expected_data, data_lazyness)
 
     def test_divide_inplace(self):
-        for (ancill_var, orig_data, data_lazyness) in self.test_combinations:
+        for ancill_var, orig_data, data_lazyness in self.test_combinations:
             ancill_var /= 10
             expected_data = orig_data / 10
             self._check(ancill_var, expected_data, data_lazyness)
 
     def test_right_divide(self):
-        for (ancill_var, orig_data, data_lazyness) in self.test_combinations:
+        for ancill_var, orig_data, data_lazyness in self.test_combinations:
             result = 10 / ancill_var
             expected_data = 10 / orig_data
             self._check(result, expected_data, data_lazyness)
 
     def test_negative(self):
-        for (ancill_var, orig_data, data_lazyness) in self.test_combinations:
+        for ancill_var, orig_data, data_lazyness in self.test_combinations:
             result = -ancill_var
             expected_data = -orig_data
             self._check(result, expected_data, data_lazyness)
diff --git a/lib/iris/tests/unit/coords/test_AuxCoord.py b/lib/iris/tests/unit/coords/test_AuxCoord.py
index e6cd8ac821..e5147659fc 100644
--- a/lib/iris/tests/unit/coords/test_AuxCoord.py
+++ b/lib/iris/tests/unit/coords/test_AuxCoord.py
@@ -370,7 +370,6 @@ def test_dtypes(self):
             points_type_name,
             bounds_type_name,
         ) in coords_all_dtypes_and_lazynesses(self, AuxCoord):
-
             sub_coord = main_coord[:2, 1]
 
             coord_dtype = main_coord.dtype
@@ -417,7 +416,6 @@ def test_lazyness(self):
             points_type_name,
             bounds_type_name,
         ) in coords_all_dtypes_and_lazynesses(self, AuxCoord):
-
             sub_coord = main_coord[:2, 1]
 
             msg = (
@@ -463,7 +461,6 @@ def test_real_data_copies(self):
             points_lazyness,
             bounds_lazyness,
         ) in coords_all_dtypes_and_lazynesses(self, AuxCoord):
-
             sub_coord = main_coord[:2, 1]
 
             msg = (
@@ -511,7 +508,6 @@ def test_lazyness(self):
             points_lazyness,
             bounds_lazyness,
         ) in coords_all_dtypes_and_lazynesses(self, AuxCoord):
-
             coord_dtype = main_coord.dtype
             copied_coord = main_coord.copy()
 
@@ -558,7 +554,6 @@ def test_realdata_copies(self):
             points_lazyness,
             bounds_lazyness,
         ) in coords_all_dtypes_and_lazynesses(self, AuxCoord):
-
             copied_coord = main_coord.copy()
 
             msg = (
diff --git a/lib/iris/tests/unit/coords/test_Coord.py b/lib/iris/tests/unit/coords/test_Coord.py
index dca6ed3c1b..72a48437ec 100644
--- a/lib/iris/tests/unit/coords/test_Coord.py
+++ b/lib/iris/tests/unit/coords/test_Coord.py
@@ -463,7 +463,6 @@ def test_lazy_nd_bounds_last(self):
         )
 
     def test_lazy_nd_points_and_bounds(self):
-
         self.setupTestArrays((3, 4))
         coord = AuxCoord(self.pts_lazy, bounds=self.bds_lazy)
 
@@ -520,7 +519,6 @@ def test_lazy_nd_noncontiguous_bounds_warning(self):
             coord.collapsed()
 
     def test_numeric_3_bounds(self):
-
         points = np.array([2.0, 6.0, 4.0])
         bounds = np.array([[1.0, 0.0, 3.0], [5.0, 4.0, 7.0], [3.0, 2.0, 5.0]])
 
@@ -544,7 +542,6 @@ def test_numeric_3_bounds(self):
         )
 
     def test_lazy_3_bounds(self):
-
         points = da.arange(3) * 2.0
         bounds = da.arange(3 * 3).reshape(3, 3)
 
diff --git a/lib/iris/tests/unit/coords/test_DimCoord.py b/lib/iris/tests/unit/coords/test_DimCoord.py
index 4298b140ea..dd0ba48f3d 100644
--- a/lib/iris/tests/unit/coords/test_DimCoord.py
+++ b/lib/iris/tests/unit/coords/test_DimCoord.py
@@ -304,7 +304,6 @@ def test_dtypes(self):
             points_type_name,
             bounds_type_name,
         ) in coords_all_dtypes_and_lazynesses(self, DimCoord):
-
             sub_coord = main_coord[:2]
 
             coord_dtype = main_coord.dtype
@@ -404,7 +403,6 @@ def test_real_data_copies(self):
             points_lazyness,
             bounds_lazyness,
         ) in coords_all_dtypes_and_lazynesses(self, DimCoord):
-
             sub_coord = main_coord[:2]
 
             msg = (
@@ -470,7 +468,6 @@ def test_realdata_readonly(self):
             points_type_name,
             bounds_type_name,
         ) in coords_all_dtypes_and_lazynesses(self, DimCoord):
-
             copied_coord = main_coord.copy()
 
             copied_points = copied_coord.core_points()
diff --git a/lib/iris/tests/unit/cube/test_Cube.py b/lib/iris/tests/unit/cube/test_Cube.py
index 5d120a6982..8e9e00dce8 100644
--- a/lib/iris/tests/unit/cube/test_Cube.py
+++ b/lib/iris/tests/unit/cube/test_Cube.py
@@ -1962,6 +1962,7 @@ def _assert_lists_equal(self, items_a, items_b):
         a different order.
 
         """
+
         # Compare (and thus sort) by their *common* metadata.
         def sortkey(item):
             return BaseMetadata.from_metadata(item.metadata)
diff --git a/lib/iris/tests/unit/experimental/ugrid/mesh/test_MeshCoord.py b/lib/iris/tests/unit/experimental/ugrid/mesh/test_MeshCoord.py
index 538cecdc7d..03e2793fd9 100644
--- a/lib/iris/tests/unit/experimental/ugrid/mesh/test_MeshCoord.py
+++ b/lib/iris/tests/unit/experimental/ugrid/mesh/test_MeshCoord.py
@@ -235,9 +235,7 @@ class Test__getitem__(tests.IrisTest):
     def test_slice_wholeslice_1tuple(self):
         # The only slicing case that we support, to enable cube slicing.
         meshcoord = sample_meshcoord()
-        meshcoord2 = meshcoord[
-            :,
-        ]
+        meshcoord2 = meshcoord[:,]
         self.assertIsNot(meshcoord2, meshcoord)
         self.assertEqual(meshcoord2, meshcoord)
         # In this case, we should *NOT* copy the linked Mesh object.
diff --git a/lib/iris/tests/unit/fileformats/nc_load_rules/actions/test__miscellaneous.py b/lib/iris/tests/unit/fileformats/nc_load_rules/actions/test__miscellaneous.py
index a8e44747dd..ffe00c8c19 100644
--- a/lib/iris/tests/unit/fileformats/nc_load_rules/actions/test__miscellaneous.py
+++ b/lib/iris/tests/unit/fileformats/nc_load_rules/actions/test__miscellaneous.py
@@ -127,7 +127,6 @@ def _make_testcase_cdl(
         include_cellmeasure=False,
         include_ancil=False,
     ):
-
         phenom_extra_attrs_string = ""
         extra_vars_string = ""
 
diff --git a/lib/iris/tests/unit/fileformats/nc_load_rules/helpers/test_build_dimension_coordinate.py b/lib/iris/tests/unit/fileformats/nc_load_rules/helpers/test_build_dimension_coordinate.py
index b485937cb1..bc13975441 100644
--- a/lib/iris/tests/unit/fileformats/nc_load_rules/helpers/test_build_dimension_coordinate.py
+++ b/lib/iris/tests/unit/fileformats/nc_load_rules/helpers/test_build_dimension_coordinate.py
@@ -229,7 +229,9 @@ def test_aux_coord_construction(self):
         warning_patch = mock.patch("warnings.warn")
 
         # Asserts must lie within context manager because of deferred loading.
-        with warning_patch, self.deferred_load_patch, self.get_cf_bounds_var_patch:
+        with (
+            warning_patch
+        ), self.deferred_load_patch, self.get_cf_bounds_var_patch:
             build_dimension_coordinate(self.engine, self.cf_coord_var)
 
             # Test that expected coord is built and added to cube.
diff --git a/lib/iris/tests/unit/fileformats/netcdf/test_Saver__ugrid.py b/lib/iris/tests/unit/fileformats/netcdf/test_Saver__ugrid.py
index 575c852ece..18e86a9f57 100644
--- a/lib/iris/tests/unit/fileformats/netcdf/test_Saver__ugrid.py
+++ b/lib/iris/tests/unit/fileformats/netcdf/test_Saver__ugrid.py
@@ -1082,7 +1082,6 @@ def test_mesh_dim_names(self):
             ("dim invalid-name &%!", "dim_invalid_name____"),
         ]
         for given_name, expected_name in dim_names_tests:
-
             mesh = make_mesh(mesh_kwargs={"face_dimension": given_name})
 
             filepath = self.check_save_mesh(mesh)
diff --git a/lib/iris/tests/unit/fileformats/pp/test_PPField.py b/lib/iris/tests/unit/fileformats/pp/test_PPField.py
index 5e2bbcaa2c..316894ded1 100644
--- a/lib/iris/tests/unit/fileformats/pp/test_PPField.py
+++ b/lib/iris/tests/unit/fileformats/pp/test_PPField.py
@@ -44,7 +44,6 @@
 
 
 class DummyPPField(PPField):
-
     HEADER_DEFN = DUMMY_HEADER
     HEADER_DICT = dict(DUMMY_HEADER)
 
diff --git a/lib/iris/tests/unit/fileformats/pp_load_rules/test__all_other_rules.py b/lib/iris/tests/unit/fileformats/pp_load_rules/test__all_other_rules.py
index 62eb7ff019..e194e240c6 100644
--- a/lib/iris/tests/unit/fileformats/pp_load_rules/test__all_other_rules.py
+++ b/lib/iris/tests/unit/fileformats/pp_load_rules/test__all_other_rules.py
@@ -211,7 +211,6 @@ def test_lbcode3x23(self):
 
 
 class TestLBTIMx2x_ZeroYears(TestField):
-
     _spec = [
         "lbtim",
         "lbcode",
diff --git a/lib/iris/tests/unit/lazy_data/test_as_lazy_data.py b/lib/iris/tests/unit/lazy_data/test_as_lazy_data.py
index 5aeebd6045..5f9dece153 100644
--- a/lib/iris/tests/unit/lazy_data/test_as_lazy_data.py
+++ b/lib/iris/tests/unit/lazy_data/test_as_lazy_data.py
@@ -68,7 +68,7 @@ def test_chunk_size_limiting(self):
             ((11, 2, 1011, 1022), (5, 2, 1011, 1022)),
         ]
         err_fmt = "Result of optimising chunks {} was {}, expected {}"
-        for (shape, expected) in given_shapes_and_resulting_chunks:
+        for shape, expected in given_shapes_and_resulting_chunks:
             chunks = _optimum_chunksize(
                 shape, shape, limit=self.FIXED_CHUNKSIZE_LIMIT
             )
@@ -86,7 +86,7 @@ def test_chunk_size_expanding(self):
             ((3, 300, 200), (117, 300, 1000), (39, 300, 1000)),
         ]
         err_fmt = "Result of optimising shape={};chunks={} was {}, expected {}"
-        for (shape, fullshape, expected) in given_shapes_and_resulting_chunks:
+        for shape, fullshape, expected in given_shapes_and_resulting_chunks:
             chunks = _optimum_chunksize(
                 chunks=shape, shape=fullshape, limit=self.FIXED_CHUNKSIZE_LIMIT
             )
diff --git a/lib/iris/tests/unit/merge/test_ProtoCube.py b/lib/iris/tests/unit/merge/test_ProtoCube.py
index 625290ad24..0fca726b28 100644
--- a/lib/iris/tests/unit/merge/test_ProtoCube.py
+++ b/lib/iris/tests/unit/merge/test_ProtoCube.py
@@ -289,7 +289,6 @@ def test_noise(self):
 
 
 class Test_register__CoordSig_general(_MergeTest, tests.IrisTest):
-
     _mergetest_type = "coord"
 
     def setUp(self):
@@ -444,7 +443,6 @@ def test_coord_system(self):
 
 
 class Test_register__CoordSig_scalar(_MergeTest_coordprops, tests.IrisTest):
-
     _mergetest_type = "aux_coords (scalar)"
 
     def setUp(self):
@@ -486,7 +484,6 @@ def test_dims(self):
 
 
 class Test_register__CoordSig_dim(_MergeTest_coordprops_vect, tests.IrisTest):
-
     _mergetest_type = "dim_coords"
     _coord_typename = "dim_coord"
 
@@ -515,7 +512,6 @@ def test_circular(self):
 
 
 class Test_register__CoordSig_aux(_MergeTest_coordprops_vect, tests.IrisTest):
-
     _mergetest_type = "aux_coords (non-scalar)"
     _coord_typename = "aux_coord"
 
diff --git a/lib/iris/util.py b/lib/iris/util.py
index 1cf41e6fb6..9e0db9e66e 100644
--- a/lib/iris/util.py
+++ b/lib/iris/util.py
@@ -735,7 +735,6 @@ def _build_full_slice_given_keys(keys, ndim):
 
     for i, key in enumerate(keys):
         if key is Ellipsis:
-
             # replace any subsequent Ellipsis objects in keys with
             # slice(None, None) as per Numpy
             keys = keys[:i] + tuple(