From 1e01a4a692cbc551b657e618900c5296c0daf619 Mon Sep 17 00:00:00 2001
From: "stephen.worsley" <stephen.worsley@metoffice.gov.uk>
Date: Tue, 5 Nov 2019 17:10:17 +0000
Subject: [PATCH 1/3] simplify class definitions

---
 .../documenting/docstrings_attribute.py          |  2 +-
 lib/iris/_concatenate.py                         |  6 +++---
 lib/iris/_constraints.py                         |  6 +++---
 lib/iris/_cube_coord_common.py                   |  2 +-
 lib/iris/_data_manager.py                        |  2 +-
 lib/iris/_merge.py                               |  2 +-
 lib/iris/analysis/__init__.py                    | 16 ++++++++--------
 lib/iris/analysis/_area_weighted.py              |  2 +-
 lib/iris/analysis/_interpolation.py              |  2 +-
 lib/iris/analysis/_regrid.py                     |  4 ++--
 lib/iris/analysis/_scipy_interpolate.py          |  2 +-
 lib/iris/analysis/maths.py                       |  2 +-
 lib/iris/analysis/trajectory.py                  |  6 +++---
 lib/iris/config.py                               |  2 +-
 lib/iris/cube.py                                 |  4 ++--
 lib/iris/experimental/regrid.py                  |  8 ++++----
 lib/iris/experimental/representation.py          |  4 ++--
 lib/iris/fileformats/_ff.py                      |  6 +++---
 .../_structured_array_identification.py          |  2 +-
 lib/iris/fileformats/abf.py                      |  2 +-
 lib/iris/fileformats/cf.py                       |  2 +-
 lib/iris/fileformats/netcdf.py                   |  8 ++++----
 lib/iris/fileformats/nimrod.py                   |  2 +-
 lib/iris/fileformats/pp.py                       |  4 ++--
 lib/iris/fileformats/rules.py                    |  2 +-
 .../um/_fast_load_structured_fields.py           |  2 +-
 lib/iris/io/format_picker.py                     |  6 +++---
 lib/iris/iterate.py                              |  2 +-
 lib/iris/tests/__init__.py                       |  2 +-
 .../integration/fast_load/test_fast_load.py      | 10 +++++-----
 .../tests/integration/plot/test_vector_plots.py  |  2 +-
 lib/iris/tests/integration/test_pickle.py        |  2 +-
 .../tests/integration/test_regrid_equivalence.py |  2 +-
 lib/iris/tests/pp.py                             |  2 +-
 lib/iris/tests/test_cdm.py                       |  4 ++--
 lib/iris/tests/test_cell.py                      |  2 +-
 lib/iris/tests/test_constraints.py               |  2 +-
 lib/iris/tests/test_coord_api.py                 |  4 ++--
 lib/iris/tests/test_cube.py                      |  2 +-
 lib/iris/tests/test_cube_to_pp.py                |  2 +-
 lib/iris/tests/test_merge.py                     |  2 +-
 lib/iris/tests/test_netcdf.py                    |  2 +-
 lib/iris/tests/test_pandas.py                    |  2 +-
 lib/iris/tests/test_plot.py                      |  6 +++---
 lib/iris/tests/test_pp_module.py                 |  6 +++---
 ...test_UnstructuredNearestNeighbourRegridder.py |  2 +-
 lib/iris/tests/unit/coords/__init__.py           |  2 +-
 lib/iris/tests/unit/cube/test_Cube.py            |  4 ++--
 .../tests/unit/fileformats/abf/test_ABFField.py  |  2 +-
 .../tests/unit/fileformats/netcdf/test_Saver.py  |  2 +-
 .../test_build_dimension_coordinate.py           |  2 +-
 .../test_ArrayStructure.py                       |  2 +-
 .../test_optimal_array_structure.py              |  2 +-
 .../unit/lazy_data/test_as_concrete_data.py      |  2 +-
 .../unit/lazy_data/test_co_realise_cubes.py      |  2 +-
 lib/iris/tests/unit/merge/test_ProtoCube.py      |  2 +-
 lib/iris/tests/unit/plot/__init__.py             |  2 +-
 lib/iris/tests/unit/plot/_blockplot_common.py    |  4 ++--
 lib/iris/tests/unit/time/test_PartialDateTime.py |  2 +-
 .../unit/util/test__slice_data_with_keys.py      |  6 +++---
 lib/iris/time.py                                 |  2 +-
 tools/translator/__init__.py                     |  2 +-
 62 files changed, 103 insertions(+), 103 deletions(-)

diff --git a/docs/iris/src/developers_guide/documenting/docstrings_attribute.py b/docs/iris/src/developers_guide/documenting/docstrings_attribute.py
index 24e4eec5d1..9c8a07b310 100644
--- a/docs/iris/src/developers_guide/documenting/docstrings_attribute.py
+++ b/docs/iris/src/developers_guide/documenting/docstrings_attribute.py
@@ -1,4 +1,4 @@
-class ExampleClass(object):
+class ExampleClass:
     """
     Class Summary
 
diff --git a/lib/iris/_concatenate.py b/lib/iris/_concatenate.py
index 322a8a0398..bd748be37f 100644
--- a/lib/iris/_concatenate.py
+++ b/lib/iris/_concatenate.py
@@ -281,7 +281,7 @@ def _none_sort(item):
     return concatenated_cubes
 
 
-class _CubeSignature(object):
+class _CubeSignature:
     """
     Template for identifying a specific type of :class:`iris.cube.Cube` based
     on its metadata, coordinates and cell_measures.
@@ -460,7 +460,7 @@ def match(self, other, error_on_mismatch):
         return match
 
 
-class _CoordSignature(object):
+class _CoordSignature:
     """
     Template for identifying a specific type of :class:`iris.cube.Cube` based
     on its coordinates.
@@ -579,7 +579,7 @@ def _calculate_extents(self):
             self.dim_extents.append(_CoordExtent(points, bounds))
 
 
-class _ProtoCube(object):
+class _ProtoCube:
     """
     Framework for concatenating multiple source-cubes over one
     common dimension.
diff --git a/lib/iris/_constraints.py b/lib/iris/_constraints.py
index dc6bd2e5d4..356d1147ad 100644
--- a/lib/iris/_constraints.py
+++ b/lib/iris/_constraints.py
@@ -17,7 +17,7 @@
 import iris.exceptions
 
 
-class Constraint(object):
+class Constraint:
     """
     Constraints are the mechanism by which cubes can be pattern matched and
     filtered according to specific criteria.
@@ -199,7 +199,7 @@ def _CIM_extract(self, cube):
                              self.rhs._CIM_extract(cube))
 
 
-class _CoordConstraint(object):
+class _CoordConstraint:
     """Represents the atomic elements which might build up a Constraint."""
     def __init__(self, coord_name, coord_thing):
         """
@@ -280,7 +280,7 @@ def call_func(c):
         return cube_cim
 
 
-class _ColumnIndexManager(object):
+class _ColumnIndexManager:
     """
     A class to represent column aligned slices which can be operated on
     using ``&``, ``|`` or ``^``.
diff --git a/lib/iris/_cube_coord_common.py b/lib/iris/_cube_coord_common.py
index e7a5c9721d..877d99de25 100644
--- a/lib/iris/_cube_coord_common.py
+++ b/lib/iris/_cube_coord_common.py
@@ -100,7 +100,7 @@ def update(self, other, **kwargs):
         dict.update(self, other, **kwargs)
 
 
-class CFVariableMixin(object):
+class CFVariableMixin:
 
     _DEFAULT_NAME = 'unknown'  # the name default string
 
diff --git a/lib/iris/_data_manager.py b/lib/iris/_data_manager.py
index 73fcc3db52..3deb0bfd1d 100644
--- a/lib/iris/_data_manager.py
+++ b/lib/iris/_data_manager.py
@@ -16,7 +16,7 @@
 from iris.util import array_equal
 
 
-class DataManager(object):
+class DataManager:
     """
     Provides a well defined API for management of real or lazy data.
 
diff --git a/lib/iris/_merge.py b/lib/iris/_merge.py
index 6460cdbb10..9c6813259c 100644
--- a/lib/iris/_merge.py
+++ b/lib/iris/_merge.py
@@ -1054,7 +1054,7 @@ def derive_space(groups, relation_matrix, positions, function_matrix=None):
     return space
 
 
-class ProtoCube(object):
+class ProtoCube:
     """
     Framework for merging source-cubes into one or more higher
     dimensional cubes.
diff --git a/lib/iris/analysis/__init__.py b/lib/iris/analysis/__init__.py
index b698eaa849..7c06483683 100644
--- a/lib/iris/analysis/__init__.py
+++ b/lib/iris/analysis/__init__.py
@@ -60,7 +60,7 @@
            'AreaWeighted', 'Nearest', 'UnstructuredNearest')
 
 
-class _CoordGroup(object):
+class _CoordGroup:
     """
     Represents a list of coordinates, one for each given cube. Which can be
     operated on conveniently.
@@ -349,7 +349,7 @@ def no_data_dim_fn(cube, coord):
     return result
 
 
-class _Aggregator(object):
+class _Aggregator:
     """
     The :class:`_Aggregator` base class provides common aggregation
     functionality.
@@ -1823,7 +1823,7 @@ def interp_order(length):
 """
 
 
-class _Groupby(object):
+class _Groupby:
     """
     Convenience class to determine group slices over one or more group-by
     coordinates.
@@ -2149,7 +2149,7 @@ def clear_phenomenon_identity(cube):
 #
 ###############################################################################
 
-class Linear(object):
+class Linear:
     """
     This class describes the linear interpolation and regridding scheme for
     interpolating or regridding over one or more orthogonal coordinates,
@@ -2272,7 +2272,7 @@ def regridder(self, src_grid, target_grid):
                                     self._normalised_extrapolation_mode())
 
 
-class AreaWeighted(object):
+class AreaWeighted:
     """
     This class describes an area-weighted regridding scheme for regridding
     between 'ordinary' horizontal grids with separated X and Y coordinates in a
@@ -2342,7 +2342,7 @@ def regridder(self, src_grid_cube, target_grid_cube):
                                      mdtol=self.mdtol)
 
 
-class Nearest(object):
+class Nearest:
     """
     This class describes the nearest-neighbour interpolation and regridding
     scheme for interpolating or regridding over one or more orthogonal
@@ -2455,7 +2455,7 @@ def regridder(self, src_grid, target_grid):
                                     self.extrapolation_mode)
 
 
-class UnstructuredNearest(object):
+class UnstructuredNearest:
     """
     This is a nearest-neighbour regridding scheme for regridding data whose
     horizontal (X- and Y-axis) coordinates are mapped to the *same* dimensions,
@@ -2546,7 +2546,7 @@ def regridder(self, src_cube, target_grid):
         return UnstructuredNearestNeigbourRegridder(src_cube, target_grid)
 
 
-class PointInCell(object):
+class PointInCell:
     """
     This class describes the point-in-cell regridding scheme for use
     typically with :meth:`iris.cube.Cube.regrid()`.
diff --git a/lib/iris/analysis/_area_weighted.py b/lib/iris/analysis/_area_weighted.py
index 23c71bd8d8..8d3ad30c91 100644
--- a/lib/iris/analysis/_area_weighted.py
+++ b/lib/iris/analysis/_area_weighted.py
@@ -11,7 +11,7 @@
 import iris.experimental.regrid as eregrid
 
 
-class AreaWeightedRegridder(object):
+class AreaWeightedRegridder:
     """
     This class provides support for performing area-weighted regridding.
 
diff --git a/lib/iris/analysis/_interpolation.py b/lib/iris/analysis/_interpolation.py
index 49fc04899d..256317c996 100644
--- a/lib/iris/analysis/_interpolation.py
+++ b/lib/iris/analysis/_interpolation.py
@@ -169,7 +169,7 @@ def snapshot_grid(cube):
     return x.copy(), y.copy()
 
 
-class RectilinearInterpolator(object):
+class RectilinearInterpolator:
     """
     This class provides support for performing nearest-neighbour or
     linear interpolation over one or more orthogonal dimensions.
diff --git a/lib/iris/analysis/_regrid.py b/lib/iris/analysis/_regrid.py
index d734083ff3..7aa816b994 100644
--- a/lib/iris/analysis/_regrid.py
+++ b/lib/iris/analysis/_regrid.py
@@ -329,7 +329,7 @@ def _regrid_weighted_curvilinear_to_rectilinear__perform(
     return cube
 
 
-class CurvilinearRegridder(object):
+class CurvilinearRegridder:
     """
     This class provides support for performing point-in-cell regridding
     between a curvilinear source grid and a rectilinear target grid.
@@ -447,7 +447,7 @@ def __call__(self, src):
         return result
 
 
-class RectilinearRegridder(object):
+class RectilinearRegridder:
     """
     This class provides support for performing nearest-neighbour or
     linear regridding between source and target grids.
diff --git a/lib/iris/analysis/_scipy_interpolate.py b/lib/iris/analysis/_scipy_interpolate.py
index 55f955c122..cf9e2621e5 100644
--- a/lib/iris/analysis/_scipy_interpolate.py
+++ b/lib/iris/analysis/_scipy_interpolate.py
@@ -43,7 +43,7 @@ def _ndim_coords_from_arrays(points, ndim=None):
 
 # source: https://github.com/scipy/scipy/blob/b94a5d5ccc08dddbc88453477ff2625\
 # 9aeaafb32/scipy/interpolate/interpolate.py#L1400
-class _RegularGridInterpolator(object):
+class _RegularGridInterpolator:
 
     """
     Interpolation on a regular grid in arbitrary dimensions
diff --git a/lib/iris/analysis/maths.py b/lib/iris/analysis/maths.py
index 73aff490c5..564a4b0107 100644
--- a/lib/iris/analysis/maths.py
+++ b/lib/iris/analysis/maths.py
@@ -841,7 +841,7 @@ def _math_op_common(cube, operation_function, new_unit, new_dtype=None,
     return new_cube
 
 
-class IFunc(object):
+class IFunc:
     """
     :class:`IFunc` class for functions that can be applied to an iris cube.
     """
diff --git a/lib/iris/analysis/trajectory.py b/lib/iris/analysis/trajectory.py
index 2395eecd0e..74396da351 100644
--- a/lib/iris/analysis/trajectory.py
+++ b/lib/iris/analysis/trajectory.py
@@ -23,7 +23,7 @@
 from iris.util import _meshgrid
 
 
-class _Segment(object):
+class _Segment:
     """A single trajectory line segment: Two points, as described in the
     Trajectory class."""
     def __init__(self, p0, p1):
@@ -41,7 +41,7 @@ def __init__(self, p0, p1):
         self.length = math.sqrt(squares)
 
 
-class Trajectory(object):
+class Trajectory:
     """A series of given waypoints with pre-calculated sample points."""
 
     def __init__(self, waypoints, sample_count=10):
@@ -656,7 +656,7 @@ def _nearest_neighbour_indices_ndcoords(cube, sample_points, cache=None):
     return result
 
 
-class UnstructuredNearestNeigbourRegridder(object):
+class UnstructuredNearestNeigbourRegridder:
     """
     Encapsulate the operation of :meth:`iris.analysis.trajectory.interpolate`
     with given source and target grids.
diff --git a/lib/iris/config.py b/lib/iris/config.py
index 54a7f35cd8..3de44161c1 100644
--- a/lib/iris/config.py
+++ b/lib/iris/config.py
@@ -108,7 +108,7 @@ def get_dir_option(section, option, default=None):
 # Runtime options
 
 
-class NetCDF(object):
+class NetCDF:
     """Control Iris NetCDF options."""
 
     def __init__(self, conventions_override=None):
diff --git a/lib/iris/cube.py b/lib/iris/cube.py
index f97d6617db..7e4f716219 100644
--- a/lib/iris/cube.py
+++ b/lib/iris/cube.py
@@ -78,7 +78,7 @@ def name(self, default='unknown'):
 XML_NAMESPACE_URI = "urn:x-iris:cubeml-0.2"
 
 
-class _CubeFilter(object):
+class _CubeFilter:
     """
     A constraint, paired with a list of cubes matching that constraint.
 
@@ -117,7 +117,7 @@ def merged(self, unique=False):
         return _CubeFilter(self.constraint, self.cubes.merge(unique))
 
 
-class _CubeFilterCollection(object):
+class _CubeFilterCollection:
     """
     A list of _CubeFilter instances.
 
diff --git a/lib/iris/experimental/regrid.py b/lib/iris/experimental/regrid.py
index 78e27c1701..bdc45cc810 100644
--- a/lib/iris/experimental/regrid.py
+++ b/lib/iris/experimental/regrid.py
@@ -823,7 +823,7 @@ def regrid_weighted_curvilinear_to_rectilinear(src_cube, weights, grid_cube):
     return result
 
 
-class PointInCell(object):
+class PointInCell:
     """
     This class describes the point-in-cell regridding scheme for use
     typically with :meth:`iris.cube.Cube.regrid()`.
@@ -857,7 +857,7 @@ def __init__(self, weights=None):
             '"iris.analysis.PointInCell".')
 
 
-class _ProjectedUnstructuredRegridder(object):
+class _ProjectedUnstructuredRegridder:
     """
     This class provides regridding that uses scipy.interpolate.griddata.
 
@@ -1163,7 +1163,7 @@ def __call__(self, src_cube):
         return new_cube
 
 
-class ProjectedUnstructuredLinear(object):
+class ProjectedUnstructuredLinear:
     """
     This class describes the linear regridding scheme which uses the
     scipy.interpolate.griddata to regrid unstructured data on to a grid.
@@ -1220,7 +1220,7 @@ def regridder(self, src_cube, target_grid):
                                                'linear', self.projection)
 
 
-class ProjectedUnstructuredNearest(object):
+class ProjectedUnstructuredNearest:
     """
     This class describes the nearest regridding scheme which uses the
     scipy.interpolate.griddata to regrid unstructured data on to a grid.
diff --git a/lib/iris/experimental/representation.py b/lib/iris/experimental/representation.py
index 21ff36f33c..5a2a29d089 100644
--- a/lib/iris/experimental/representation.py
+++ b/lib/iris/experimental/representation.py
@@ -13,7 +13,7 @@
 import re
 
 
-class CubeRepresentation(object):
+class CubeRepresentation:
     """
     Produce representations of a :class:`~iris.cube.Cube`.
 
@@ -327,7 +327,7 @@ def repr_html(self):
                                      content=content)
 
 
-class CubeListRepresentation(object):
+class CubeListRepresentation:
     _template = """
 <style>
     .accordion-{uid} {{
diff --git a/lib/iris/fileformats/_ff.py b/lib/iris/fileformats/_ff.py
index e26477510c..7214a4668f 100644
--- a/lib/iris/fileformats/_ff.py
+++ b/lib/iris/fileformats/_ff.py
@@ -113,7 +113,7 @@
 REAL_POLE_LON = 5
 
 
-class Grid(object):
+class Grid:
     """
     An abstract class representing the default/file-level grid
     definition for a FieldsFile.
@@ -286,7 +286,7 @@ def _y_vectors(self):
         return y_p, y_v
 
 
-class FFHeader(object):
+class FFHeader:
     """
     A class to represent the FIXED_LENGTH_HEADER section of a FieldsFile.
 
@@ -417,7 +417,7 @@ def grid(self):
         return grid
 
 
-class FF2PP(object):
+class FF2PP:
     """
     A class to extract the individual PPFields from within a FieldsFile.
 
diff --git a/lib/iris/fileformats/_structured_array_identification.py b/lib/iris/fileformats/_structured_array_identification.py
index 7e13c05e93..e727201285 100644
--- a/lib/iris/fileformats/_structured_array_identification.py
+++ b/lib/iris/fileformats/_structured_array_identification.py
@@ -286,7 +286,7 @@ def from_array(cls, arr):
         return structure
 
 
-class GroupStructure(object):
+class GroupStructure:
     """
     The GroupStructure class represents a collection of array structures along
     with additional information such as the length of the arrays and the array
diff --git a/lib/iris/fileformats/abf.py b/lib/iris/fileformats/abf.py
index cade3b0e5a..401a160dd4 100644
--- a/lib/iris/fileformats/abf.py
+++ b/lib/iris/fileformats/abf.py
@@ -37,7 +37,7 @@
                  "jul": 7, "aug": 8, "sep": 9, "oct": 10, "nov": 11, "dec": 12}
 
 
-class ABFField(object):
+class ABFField:
     """
     A data field from an ABF (or ABL) file.
 
diff --git a/lib/iris/fileformats/cf.py b/lib/iris/fileformats/cf.py
index 70bdc25754..3d3cde8896 100644
--- a/lib/iris/fileformats/cf.py
+++ b/lib/iris/fileformats/cf.py
@@ -901,7 +901,7 @@ def __repr__(self):
 
 
 ################################################################################
-class CFReader(object):
+class CFReader:
     """
     This class allows the contents of a netCDF file to be interpreted according
     to the 'NetCDF Climate and Forecast (CF) Metadata Conventions'.
diff --git a/lib/iris/fileformats/netcdf.py b/lib/iris/fileformats/netcdf.py
index 3ef26d3ca5..bcb875b07f 100644
--- a/lib/iris/fileformats/netcdf.py
+++ b/lib/iris/fileformats/netcdf.py
@@ -243,7 +243,7 @@ def parse_cell_methods(nc_cell_methods):
     return tuple(cell_methods)
 
 
-class CFNameCoordMap(object):
+class CFNameCoordMap:
     """Provide a simple CF name to CF coordinate mapping."""
 
     _Map = collections.namedtuple('_Map', ['name', 'coord'])
@@ -355,7 +355,7 @@ def _pyke_kb_engine():
     return engine
 
 
-class NetCDFDataProxy(object):
+class NetCDFDataProxy:
     """A reference to the data payload of a single NetCDF file variable."""
 
     __slots__ = ('shape', 'dtype', 'path', 'variable_name', 'fill_value')
@@ -742,7 +742,7 @@ def _setncattr(variable, name, attribute):
     return variable.setncattr(name, attribute)
 
 
-class _FillValueMaskCheckAndStoreTarget(object):
+class _FillValueMaskCheckAndStoreTarget:
     """
     To be used with da.store. Remembers whether any element was equal to a
     given value and whether it was masked, before passing the chunk to the
@@ -762,7 +762,7 @@ def __setitem__(self, keys, arr):
         self.target[keys] = arr
 
 
-class Saver(object):
+class Saver:
     """A manager for saving netcdf files."""
 
     def __init__(self, filename, netcdf_format):
diff --git a/lib/iris/fileformats/nimrod.py b/lib/iris/fileformats/nimrod.py
index 6b85e89545..a97696ea7c 100644
--- a/lib/iris/fileformats/nimrod.py
+++ b/lib/iris/fileformats/nimrod.py
@@ -71,7 +71,7 @@ def _read_chars(infile, num):
     return result
 
 
-class NimrodField(object):
+class NimrodField:
     """
     A data field from a NIMROD file.
 
diff --git a/lib/iris/fileformats/pp.py b/lib/iris/fileformats/pp.py
index 3ebea0e606..ddb64a1cda 100644
--- a/lib/iris/fileformats/pp.py
+++ b/lib/iris/fileformats/pp.py
@@ -326,7 +326,7 @@ def __ne__(self, other):
         return not self.__eq__(other)
 
 
-class SplittableInt(object):
+class SplittableInt:
     """
     A class to hold integers which can easily get each decimal digit
     individually.
@@ -507,7 +507,7 @@ def __ge__(self, other):
         return self._compare(other, operator.ge)
 
 
-class PPDataProxy(object):
+class PPDataProxy:
     """A reference to the data payload of a single PP field."""
 
     __slots__ = ('shape', 'src_dtype', 'path', 'offset', 'data_len',
diff --git a/lib/iris/fileformats/rules.py b/lib/iris/fileformats/rules.py
index 436b2ee01e..31abc2e97e 100644
--- a/lib/iris/fileformats/rules.py
+++ b/lib/iris/fileformats/rules.py
@@ -23,7 +23,7 @@
                                          ('name', 'transform'))
 
 
-class ConcreteReferenceTarget(object):
+class ConcreteReferenceTarget:
     """Everything you need to make a real Cube for a named reference."""
 
     def __init__(self, name, transform=None):
diff --git a/lib/iris/fileformats/um/_fast_load_structured_fields.py b/lib/iris/fileformats/um/_fast_load_structured_fields.py
index 06bf07c9bb..ad5425f296 100644
--- a/lib/iris/fileformats/um/_fast_load_structured_fields.py
+++ b/lib/iris/fileformats/um/_fast_load_structured_fields.py
@@ -22,7 +22,7 @@
     optimal_array_structure
 
 
-class BasicFieldCollation(object):
+class BasicFieldCollation:
     """
     An object representing a group of UM fields with array structure that can
     be vectorized into a single cube.
diff --git a/lib/iris/io/format_picker.py b/lib/iris/io/format_picker.py
index bc72e11aad..419847c2c3 100644
--- a/lib/iris/io/format_picker.py
+++ b/lib/iris/io/format_picker.py
@@ -49,7 +49,7 @@
 import iris.io
 
 
-class FormatAgent(object):
+class FormatAgent:
     """
     The FormatAgent class is the containing object which is responsible for identifying the format of a given file
     by interrogating its children FormatSpecification instances.
@@ -138,7 +138,7 @@ def get_spec(self, basename, buffer_obj):
 
 
 @functools.total_ordering
-class FormatSpecification(object):
+class FormatSpecification:
     """
     Provides the base class for file type definition.
 
@@ -225,7 +225,7 @@ def __str__(self):
         return '%s%s (priority %s)' % (self.name, ' (no handler available)' if self.handler is None else '',  self.priority)
 
 
-class FileElement(object):
+class FileElement:
     """
     Represents a specific aspect of a FileFormat which can be identified using the given element getter function.
 
diff --git a/lib/iris/iterate.py b/lib/iris/iterate.py
index c44df38a86..d43c5a1ccb 100644
--- a/lib/iris/iterate.py
+++ b/lib/iris/iterate.py
@@ -260,7 +260,7 @@ def __next__(self):
     next = __next__
 
 
-class _CoordWrapper(object):
+class _CoordWrapper:
     """
     Class for creating a coordinate wrapper that allows the use of an
     alternative equality function based on metadata rather than
diff --git a/lib/iris/tests/__init__.py b/lib/iris/tests/__init__.py
index be6347fdff..4411cb3ffa 100644
--- a/lib/iris/tests/__init__.py
+++ b/lib/iris/tests/__init__.py
@@ -984,7 +984,7 @@ class IrisTest(IrisTest_nometa, metaclass=_TestTimingsMetaclass):
 get_result_path = IrisTest.get_result_path
 
 
-class GraphicsTestMixin(object):
+class GraphicsTestMixin:
 
     # nose directive: dispatch tests concurrently.
     _multiprocess_can_split_ = True
diff --git a/lib/iris/tests/integration/fast_load/test_fast_load.py b/lib/iris/tests/integration/fast_load/test_fast_load.py
index a04f503dfe..47483396dd 100644
--- a/lib/iris/tests/integration/fast_load/test_fast_load.py
+++ b/lib/iris/tests/integration/fast_load/test_fast_load.py
@@ -31,7 +31,7 @@
 from iris.fileformats.um import structured_um_loading
 
 
-class Mixin_FieldTest(object):
+class Mixin_FieldTest:
     # A mixin providing common facilities for fast-load testing :
     #   * create 'raw' cubes to produce the desired PP fields in a test file.
     #   * save 'raw' cubes to temporary PP files that get deleted afterwards.
@@ -245,7 +245,7 @@ def add_arg_coords(arg, name, unit, vals=None):
         return cubes
 
 
-class MixinBasic(object):
+class MixinBasic:
     # A mixin of tests that can be applied to *either* standard or fast load.
     # The "real" test classes must inherit this, and Mixin_FieldTest,
     # and define 'self.do_fast_loads' as True or False.
@@ -290,7 +290,7 @@ def test_cell_method(self):
         self.assertEqual(results, expected)
 
 
-class MixinCallDetails(object):
+class MixinCallDetails:
     # A mixin of tests that can be applied to *either* standard or fast load.
     # The "real" test classes must inherit this, and Mixin_FieldTest,
     # and define 'self.do_fast_loads' as True or False.
@@ -427,7 +427,7 @@ def timeorder(cube):
         self.assertEqual(results, expected)
 
 
-class MixinDimsAndOrdering(object):
+class MixinDimsAndOrdering:
     # A mixin of tests that can be applied to *either* standard or fast load.
     # The "real" test classes must inherit this, and Mixin_FieldTest,
     # and define 'self.do_fast_loads' as True or False.
@@ -507,7 +507,7 @@ def test_missing_combination(self):
         self.assertEqual(results, expected)
 
 
-class MixinProblemCases(object):
+class MixinProblemCases:
     def test_FAIL_scalar_vector_concatenate(self):
         # Structured load can produce a scalar coordinate from one file, and a
         # matching vector one from another file, but these won't "combine".
diff --git a/lib/iris/tests/integration/plot/test_vector_plots.py b/lib/iris/tests/integration/plot/test_vector_plots.py
index 6c9eaa4b41..c4bf26b82f 100644
--- a/lib/iris/tests/integration/plot/test_vector_plots.py
+++ b/lib/iris/tests/integration/plot/test_vector_plots.py
@@ -27,7 +27,7 @@
 
 
 @tests.skip_plot
-class MixinVectorPlotCases(object):
+class MixinVectorPlotCases:
     """
     Test examples mixin, used by separate quiver + streamplot classes.
 
diff --git a/lib/iris/tests/integration/test_pickle.py b/lib/iris/tests/integration/test_pickle.py
index ba66d2c24a..0a55ad3736 100644
--- a/lib/iris/tests/integration/test_pickle.py
+++ b/lib/iris/tests/integration/test_pickle.py
@@ -18,7 +18,7 @@
     from iris_grib.message import GribMessage
 
 
-class Common(object):
+class Common:
     def pickle_cube(self, protocol):
         # Ensure that data proxies are pickleable.
         cube = iris.load(self.path)[0]
diff --git a/lib/iris/tests/integration/test_regrid_equivalence.py b/lib/iris/tests/integration/test_regrid_equivalence.py
index 6c802a4d4a..48c20f30be 100644
--- a/lib/iris/tests/integration/test_regrid_equivalence.py
+++ b/lib/iris/tests/integration/test_regrid_equivalence.py
@@ -50,7 +50,7 @@ def _debug_data(cube, test_id):
         print(repr(data))
 
 
-class MixinCheckingCode(object):
+class MixinCheckingCode:
     def test_basic(self):
         src_x = [30., 40., 50.]
         dst_x = [32., 42.]
diff --git a/lib/iris/tests/pp.py b/lib/iris/tests/pp.py
index 7c1b012386..f198995b61 100644
--- a/lib/iris/tests/pp.py
+++ b/lib/iris/tests/pp.py
@@ -11,7 +11,7 @@
 import iris.tests as tests
 
 
-class PPTest(object):
+class PPTest:
     """
     A mixin class to provide PP-specific utilities to subclasses of tests.IrisTest.
 
diff --git a/lib/iris/tests/test_cdm.py b/lib/iris/tests/test_cdm.py
index 2cd7e15224..af229103a3 100644
--- a/lib/iris/tests/test_cdm.py
+++ b/lib/iris/tests/test_cdm.py
@@ -793,7 +793,7 @@ def test_metadata_dict(self):
         self.assertEqual(self.t.cell_methods, ())
 
     def test_metadata_attrs(self):
-        class Metadata(object): pass
+        class Metadata: pass
         metadata = Metadata()
         metadata.standard_name = 'air_pressure'
         metadata.long_name = 'foo'
@@ -824,7 +824,7 @@ def test_metadata_fail(self):
                                'units': '',
                                'attributes': {'random': '12'}}
         with self.assertRaises(TypeError):
-            class Metadata(object): pass
+            class Metadata: pass
             metadata = Metadata()
             metadata.standard_name = 'air_pressure'
             metadata.long_name = 'foo'
diff --git a/lib/iris/tests/test_cell.py b/lib/iris/tests/test_cell.py
index e9bafeff11..9e7b41bde6 100644
--- a/lib/iris/tests/test_cell.py
+++ b/lib/iris/tests/test_cell.py
@@ -108,7 +108,7 @@ def test_coord_equality(self):
         self.assertTrue(self.d < 2)
         
         # Ensure the Cell's operators return NotImplemented.
-        class Terry(object): pass
+        class Terry: pass
         self.assertEqual(self.d.__eq__(Terry()), NotImplemented)
         self.assertEqual(self.d.__ne__(Terry()), NotImplemented)
 
diff --git a/lib/iris/tests/test_constraints.py b/lib/iris/tests/test_constraints.py
index 79ee51c9c4..8851ea2d98 100644
--- a/lib/iris/tests/test_constraints.py
+++ b/lib/iris/tests/test_constraints.py
@@ -89,7 +89,7 @@ def test_cell_different_bounds(self):
         self.assertEqual(len(sub_list), 0)
 
 
-class TestMixin(object):
+class TestMixin:
     """
     Mix-in class for attributes & utilities common to the "normal" and "strict" test cases.
 
diff --git a/lib/iris/tests/test_coord_api.py b/lib/iris/tests/test_coord_api.py
index e0ea341b10..2ac5bbeadc 100644
--- a/lib/iris/tests/test_coord_api.py
+++ b/lib/iris/tests/test_coord_api.py
@@ -879,7 +879,7 @@ def test_is_ignore(self):
 
 class TestAuxCoordEquality(tests.IrisTest):
     def test_not_implmemented(self):
-        class Terry(object):
+        class Terry:
             pass
         aux = iris.coords.AuxCoord(0)
         self.assertIs(aux.__eq__(Terry()), NotImplemented)
@@ -888,7 +888,7 @@ class Terry(object):
 
 class TestDimCoordEquality(tests.IrisTest):
     def test_not_implmemented(self):
-        class Terry(object):
+        class Terry:
             pass
         dim = iris.coords.DimCoord(0)
         aux = iris.coords.AuxCoord(0)
diff --git a/lib/iris/tests/test_cube.py b/lib/iris/tests/test_cube.py
index 79f618891d..6f3bf1b9c3 100644
--- a/lib/iris/tests/test_cube.py
+++ b/lib/iris/tests/test_cube.py
@@ -78,7 +78,7 @@ def test_adding_aux_coord(self):
 
 class TestEquality(tests.IrisTest):
     def test_not_implmemented(self):
-        class Terry(object):
+        class Terry:
             pass
         cube = iris.cube.Cube(0)
         self.assertIs(cube.__eq__(Terry()), NotImplemented)
diff --git a/lib/iris/tests/test_cube_to_pp.py b/lib/iris/tests/test_cube_to_pp.py
index aa7b21ae26..35c24d8050 100644
--- a/lib/iris/tests/test_cube_to_pp.py
+++ b/lib/iris/tests/test_cube_to_pp.py
@@ -173,7 +173,7 @@ def test_365_calendar_export(self):
         self.assertEqual(pp_field.lbtim.ic, 4)
 
 
-class FakePPEnvironment(object):
+class FakePPEnvironment:
     ''' fake a minimal PP environment for use in cross-section coords, as in PP save rules '''
     y = [1, 2, 3, 4]
     z = [111, 222, 333, 444]
diff --git a/lib/iris/tests/test_merge.py b/lib/iris/tests/test_merge.py
index 24d8e170ed..57fe755047 100644
--- a/lib/iris/tests/test_merge.py
+++ b/lib/iris/tests/test_merge.py
@@ -25,7 +25,7 @@
 import iris.tests.stock
 
 
-class TestMixin(object):
+class TestMixin:
     """
     Mix-in class for attributes & utilities common to these test cases.
 
diff --git a/lib/iris/tests/test_netcdf.py b/lib/iris/tests/test_netcdf.py
index 09deb53ba3..936c56f1b4 100644
--- a/lib/iris/tests/test_netcdf.py
+++ b/lib/iris/tests/test_netcdf.py
@@ -246,7 +246,7 @@ def test_units(self):
 
 class TestNetCDFCRS(tests.IrisTest):
     def setUp(self):
-        class Var(object):
+        class Var:
             pass
 
         self.grid = Var()
diff --git a/lib/iris/tests/test_pandas.py b/lib/iris/tests/test_pandas.py
index 5988059eb3..dd5d9e5ae4 100644
--- a/lib/iris/tests/test_pandas.py
+++ b/lib/iris/tests/test_pandas.py
@@ -294,7 +294,7 @@ def test_series_simple(self):
             tests.get_result_path(('pandas', 'as_cube', 'series_simple.cml')))
 
     def test_series_object(self):
-        class Thing(object):
+        class Thing:
             def __repr__(self):
                 return "A Thing"
         series = pandas.Series(
diff --git a/lib/iris/tests/test_plot.py b/lib/iris/tests/test_plot.py
index be89d59566..743feddca3 100644
--- a/lib/iris/tests/test_plot.py
+++ b/lib/iris/tests/test_plot.py
@@ -415,7 +415,7 @@ def _date_series(src_cube):
 
 
 @tests.skip_plot
-class SliceMixin(object):
+class SliceMixin:
     """Mixin class providing tests for each 2-dimensional permutation of axes.
 
     Requires self.draw_method to be the relevant plotting function,
@@ -598,7 +598,7 @@ def setUp(self):
 
 
 @tests.skip_plot
-class Slice1dMixin(object):
+class Slice1dMixin:
     """Mixin class providing tests for each 1-dimensional permutation of axes.
 
     Requires self.draw_method to be the relevant plotting function,
@@ -671,7 +671,7 @@ def load_cube_once(filename, constraint):
     return cube
 
 
-class LambdaStr(object):
+class LambdaStr:
     """Provides a callable function which has a sensible __repr__."""
     def __init__(self, repr, lambda_fn):
         self.repr = repr
diff --git a/lib/iris/tests/test_pp_module.py b/lib/iris/tests/test_pp_module.py
index cdcb5ebdec..5712e305b2 100644
--- a/lib/iris/tests/test_pp_module.py
+++ b/lib/iris/tests/test_pp_module.py
@@ -404,7 +404,7 @@ def test_negative_number(self):
             
 class TestSplittableIntEquality(tests.IrisTest):
     def test_not_implemented(self):
-        class Terry(object): pass
+        class Terry: pass
         sin = pp.SplittableInt(0)
         self.assertIs(sin.__eq__(Terry()), NotImplemented)
         self.assertIs(sin.__ne__(Terry()), NotImplemented)
@@ -412,7 +412,7 @@ class Terry(object): pass
 
 class TestPPDataProxyEquality(tests.IrisTest):
     def test_not_implemented(self):
-        class Terry(object): pass
+        class Terry: pass
         pox = pp.PPDataProxy("john", "michael", "eric", "graham", "brian",
                              "spam", "beans", "eggs")
         self.assertIs(pox.__eq__(Terry()), NotImplemented)
@@ -421,7 +421,7 @@ class Terry(object): pass
 
 class TestPPFieldEquality(tests.IrisTest):
     def test_not_implemented(self):
-        class Terry(object): pass
+        class Terry: pass
         pox = pp.PPField3()
         self.assertIs(pox.__eq__(Terry()), NotImplemented)
         self.assertIs(pox.__ne__(Terry()), NotImplemented)
diff --git a/lib/iris/tests/unit/analysis/trajectory/test_UnstructuredNearestNeighbourRegridder.py b/lib/iris/tests/unit/analysis/trajectory/test_UnstructuredNearestNeighbourRegridder.py
index 34c9ed8015..c8f88dff57 100644
--- a/lib/iris/tests/unit/analysis/trajectory/test_UnstructuredNearestNeighbourRegridder.py
+++ b/lib/iris/tests/unit/analysis/trajectory/test_UnstructuredNearestNeighbourRegridder.py
@@ -26,7 +26,7 @@
     UnstructuredNearestNeigbourRegridder as unn_gridder
 
 
-class MixinExampleSetup(object):
+class MixinExampleSetup:
     # Common code for regridder test classes.
 
     def setUp(self):
diff --git a/lib/iris/tests/unit/coords/__init__.py b/lib/iris/tests/unit/coords/__init__.py
index 9cad3d7a07..23e415ec2b 100644
--- a/lib/iris/tests/unit/coords/__init__.py
+++ b/lib/iris/tests/unit/coords/__init__.py
@@ -103,7 +103,7 @@ def coords_all_dtypes_and_lazynesses(self, coord_class):
                 yield result
 
 
-class CoordTestMixin(object):
+class CoordTestMixin:
     def setupTestArrays(self, shape=(3,), masked=False):
         setup_test_arrays(self, shape=shape, masked=masked)
 
diff --git a/lib/iris/tests/unit/cube/test_Cube.py b/lib/iris/tests/unit/cube/test_Cube.py
index 7d9b65f2ae..446d0e6b50 100644
--- a/lib/iris/tests/unit/cube/test_Cube.py
+++ b/lib/iris/tests/unit/cube/test_Cube.py
@@ -1496,14 +1496,14 @@ def test(self):
         # Define a fake scheme and its associated regridder which just
         # capture their arguments and return them in place of the
         # regridded cube.
-        class FakeRegridder(object):
+        class FakeRegridder:
             def __init__(self, *args):
                 self.args = args
 
             def __call__(self, cube):
                 return self.args + (cube,)
 
-        class FakeScheme(object):
+        class FakeScheme:
             def regridder(self, src, target):
                 return FakeRegridder(self, src, target)
 
diff --git a/lib/iris/tests/unit/fileformats/abf/test_ABFField.py b/lib/iris/tests/unit/fileformats/abf/test_ABFField.py
index 56d45fd031..7128c03de6 100644
--- a/lib/iris/tests/unit/fileformats/abf/test_ABFField.py
+++ b/lib/iris/tests/unit/fileformats/abf/test_ABFField.py
@@ -14,7 +14,7 @@
 from iris.fileformats.abf import ABFField
 
 
-class MethodCounter(object):
+class MethodCounter:
     def __init__(self, method_name):
         self.method_name = method_name
         self.count = 0
diff --git a/lib/iris/tests/unit/fileformats/netcdf/test_Saver.py b/lib/iris/tests/unit/fileformats/netcdf/test_Saver.py
index 45f306979c..43b0925638 100644
--- a/lib/iris/tests/unit/fileformats/netcdf/test_Saver.py
+++ b/lib/iris/tests/unit/fileformats/netcdf/test_Saver.py
@@ -550,7 +550,7 @@ def test_no_hyphen(self):
                          'valid_netcdf')
 
 
-class _Common__check_attribute_compliance(object):
+class _Common__check_attribute_compliance:
     def setUp(self):
         self.container = mock.Mock(name='container', attributes={})
         self.data = np.array(1, dtype='int32')
diff --git a/lib/iris/tests/unit/fileformats/pyke_rules/compiled_krb/fc_rules_cf_fc/test_build_dimension_coordinate.py b/lib/iris/tests/unit/fileformats/pyke_rules/compiled_krb/fc_rules_cf_fc/test_build_dimension_coordinate.py
index 37af34c8b8..1917034a6b 100644
--- a/lib/iris/tests/unit/fileformats/pyke_rules/compiled_krb/fc_rules_cf_fc/test_build_dimension_coordinate.py
+++ b/lib/iris/tests/unit/fileformats/pyke_rules/compiled_krb/fc_rules_cf_fc/test_build_dimension_coordinate.py
@@ -23,7 +23,7 @@
     build_dimension_coordinate
 
 
-class RulesTestMixin(object):
+class RulesTestMixin:
     def setUp(self):
         # Create dummy pyke engine.
         self.engine = mock.Mock(
diff --git a/lib/iris/tests/unit/fileformats/structured_array_identification/test_ArrayStructure.py b/lib/iris/tests/unit/fileformats/structured_array_identification/test_ArrayStructure.py
index 4302e66173..a071f8c0ae 100644
--- a/lib/iris/tests/unit/fileformats/structured_array_identification/test_ArrayStructure.py
+++ b/lib/iris/tests/unit/fileformats/structured_array_identification/test_ArrayStructure.py
@@ -128,7 +128,7 @@ def test_multi_dim_array(self):
             ArrayStructure.from_array(np.arange(12).reshape(3, 4))
 
 
-class nd_array_and_dims_cases(object):
+class nd_array_and_dims_cases:
     """
     Defines the test functionality for nd_array_and_dims. This class
     isn't actually the test case - see the C order and F order subclasses
diff --git a/lib/iris/tests/unit/fileformats/um/optimal_array_structuring/test_optimal_array_structure.py b/lib/iris/tests/unit/fileformats/um/optimal_array_structuring/test_optimal_array_structure.py
index 392c7c83fe..e2932312f3 100644
--- a/lib/iris/tests/unit/fileformats/um/optimal_array_structuring/test_optimal_array_structure.py
+++ b/lib/iris/tests/unit/fileformats/um/optimal_array_structuring/test_optimal_array_structure.py
@@ -19,7 +19,7 @@
     optimal_array_structure, _optimal_dimensioning_structure
 
 
-class Test__optimal_dimensioning_structure(object):
+class Test__optimal_dimensioning_structure:
     pass
 
 
diff --git a/lib/iris/tests/unit/lazy_data/test_as_concrete_data.py b/lib/iris/tests/unit/lazy_data/test_as_concrete_data.py
index ca81eab4e6..8f471d4029 100644
--- a/lib/iris/tests/unit/lazy_data/test_as_concrete_data.py
+++ b/lib/iris/tests/unit/lazy_data/test_as_concrete_data.py
@@ -15,7 +15,7 @@
 from iris._lazy_data import as_concrete_data, as_lazy_data, is_lazy_data
 
 
-class MyProxy(object):
+class MyProxy:
     def __init__(self, a):
         self.shape = a.shape
         self.dtype = a.dtype
diff --git a/lib/iris/tests/unit/lazy_data/test_co_realise_cubes.py b/lib/iris/tests/unit/lazy_data/test_co_realise_cubes.py
index a183ec2950..2d7b32dd75 100644
--- a/lib/iris/tests/unit/lazy_data/test_co_realise_cubes.py
+++ b/lib/iris/tests/unit/lazy_data/test_co_realise_cubes.py
@@ -17,7 +17,7 @@
 from iris._lazy_data import co_realise_cubes
 
 
-class ArrayAccessCounter(object):
+class ArrayAccessCounter:
     def __init__(self, array):
         self.dtype = array.dtype
         self.shape = array.shape
diff --git a/lib/iris/tests/unit/merge/test_ProtoCube.py b/lib/iris/tests/unit/merge/test_ProtoCube.py
index b1fe650933..1cdca4080d 100644
--- a/lib/iris/tests/unit/merge/test_ProtoCube.py
+++ b/lib/iris/tests/unit/merge/test_ProtoCube.py
@@ -246,7 +246,7 @@ def cube2(self):
         return cube
 
 
-class _MergeTest(object):
+class _MergeTest:
     # A mixin test class for common test methods implementation.
 
     # used by check routine: inheritors must implement it
diff --git a/lib/iris/tests/unit/plot/__init__.py b/lib/iris/tests/unit/plot/__init__.py
index f8361929d8..90e5ff03c5 100644
--- a/lib/iris/tests/unit/plot/__init__.py
+++ b/lib/iris/tests/unit/plot/__init__.py
@@ -53,7 +53,7 @@ def assertPointsTickLabels(self, axis, axes=None):
 
 
 @tests.skip_plot
-class MixinCoords(object):
+class MixinCoords:
     """
     Mixin class of common plotting tests providing 2-dimensional
     permutations of coordinates and anonymous dimensions.
diff --git a/lib/iris/tests/unit/plot/_blockplot_common.py b/lib/iris/tests/unit/plot/_blockplot_common.py
index 8fd3974e80..5753a9c0ed 100644
--- a/lib/iris/tests/unit/plot/_blockplot_common.py
+++ b/lib/iris/tests/unit/plot/_blockplot_common.py
@@ -17,7 +17,7 @@
 from iris.tests.unit.plot import MixinCoords
 
 
-class MixinStringCoordPlot(object):
+class MixinStringCoordPlot:
     # Mixin for common string-coord tests on pcolor/pcolormesh.
     # To use, make a class that inherits from this *and*
     # :class:`iris.tests.unit.plot.TestGraphicStringCoord`,
@@ -78,7 +78,7 @@ def blockplot_setup(self):
         self.mpl_patch = self.patch(patch_target_name)
 
 
-class Mixin2dCoordsContigTol(object):
+class Mixin2dCoordsContigTol:
     # Mixin for contiguity tolerance argument to pcolor/pcolormesh.
     # To use, make a class that inherits from this *and*
     # :class:`iris.tests.IrisTest`,
diff --git a/lib/iris/tests/unit/time/test_PartialDateTime.py b/lib/iris/tests/unit/time/test_PartialDateTime.py
index 52aa85d986..d31ddad120 100644
--- a/lib/iris/tests/unit/time/test_PartialDateTime.py
+++ b/lib/iris/tests/unit/time/test_PartialDateTime.py
@@ -60,7 +60,7 @@ def test_exists(self):
         self.assertTrue(hasattr(pd, 'timetuple'))
 
 
-class _Test_operator(object):
+class _Test_operator:
     def test_invalid_type(self):
         pdt = PartialDateTime()
         with self.assertRaises(TypeError):
diff --git a/lib/iris/tests/unit/util/test__slice_data_with_keys.py b/lib/iris/tests/unit/util/test__slice_data_with_keys.py
index dcbdec6d89..4f81d4baf6 100644
--- a/lib/iris/tests/unit/util/test__slice_data_with_keys.py
+++ b/lib/iris/tests/unit/util/test__slice_data_with_keys.py
@@ -24,7 +24,7 @@
 from iris._lazy_data import as_lazy_data, as_concrete_data
 
 
-class DummyArray(object):
+class DummyArray:
     # A dummy array-like that records the keys of indexing calls.
     def __init__(self, shape, _indexing_record_list=None):
         self.shape = shape
@@ -45,7 +45,7 @@ def __getitem__(self, keys):
                           _indexing_record_list=self._getitem_call_keys)
 
 
-class Indexer(object):
+class Indexer:
     # An object to make __getitem__ arglists from indexing operations.
     def __getitem__(self, keys):
         return keys
@@ -55,7 +55,7 @@ def __getitem__(self, keys):
 Index = Indexer()
 
 
-class MixinIndexingTest(object):
+class MixinIndexingTest:
     def check(self, shape, keys, expect_call_keys=None, expect_map=None):
         data = DummyArray(shape)
         dim_map, _ = _slice_data_with_keys(data, keys)
diff --git a/lib/iris/time.py b/lib/iris/time.py
index 38e1366007..a509db9336 100644
--- a/lib/iris/time.py
+++ b/lib/iris/time.py
@@ -12,7 +12,7 @@
 
 
 @functools.total_ordering
-class PartialDateTime(object):
+class PartialDateTime:
     """
     A :class:`PartialDateTime` object specifies values for some subset of
     the calendar/time fields (year, month, hour, etc.) for comparing
diff --git a/tools/translator/__init__.py b/tools/translator/__init__.py
index 689b184785..254ddd518f 100644
--- a/tools/translator/__init__.py
+++ b/tools/translator/__init__.py
@@ -38,7 +38,7 @@ def dowork(self, resource):
         resource.encode(self.fuseki_process)
 
 
-class EncodableMap(object):
+class EncodableMap:
     """
     A metarelate mapping able to encode itself as a string for use in Iris,
     as defined by a translator Mappings subclass

From f78c3e1d86693e457bff3a21f23d6573315d7424 Mon Sep 17 00:00:00 2001
From: "stephen.worsley" <stephen.worsley@metoffice.gov.uk>
Date: Wed, 6 Nov 2019 16:41:58 +0000
Subject: [PATCH 2/3] reformat for stickler

---
 lib/iris/tests/test_cdm.py       | 6 ++++--
 lib/iris/tests/test_cell.py      | 3 ++-
 lib/iris/tests/test_pp_module.py | 9 ++++++---
 3 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/lib/iris/tests/test_cdm.py b/lib/iris/tests/test_cdm.py
index af229103a3..eedb86714a 100644
--- a/lib/iris/tests/test_cdm.py
+++ b/lib/iris/tests/test_cdm.py
@@ -793,7 +793,8 @@ def test_metadata_dict(self):
         self.assertEqual(self.t.cell_methods, ())
 
     def test_metadata_attrs(self):
-        class Metadata: pass
+        class Metadata:
+            pass
         metadata = Metadata()
         metadata.standard_name = 'air_pressure'
         metadata.long_name = 'foo'
@@ -824,7 +825,8 @@ def test_metadata_fail(self):
                                'units': '',
                                'attributes': {'random': '12'}}
         with self.assertRaises(TypeError):
-            class Metadata: pass
+            class Metadata:
+                pass
             metadata = Metadata()
             metadata.standard_name = 'air_pressure'
             metadata.long_name = 'foo'
diff --git a/lib/iris/tests/test_cell.py b/lib/iris/tests/test_cell.py
index 9e7b41bde6..8daab3f3b0 100644
--- a/lib/iris/tests/test_cell.py
+++ b/lib/iris/tests/test_cell.py
@@ -108,7 +108,8 @@ def test_coord_equality(self):
         self.assertTrue(self.d < 2)
         
         # Ensure the Cell's operators return NotImplemented.
-        class Terry: pass
+        class Terry:
+            pass
         self.assertEqual(self.d.__eq__(Terry()), NotImplemented)
         self.assertEqual(self.d.__ne__(Terry()), NotImplemented)
 
diff --git a/lib/iris/tests/test_pp_module.py b/lib/iris/tests/test_pp_module.py
index 5712e305b2..9e59feb032 100644
--- a/lib/iris/tests/test_pp_module.py
+++ b/lib/iris/tests/test_pp_module.py
@@ -404,7 +404,8 @@ def test_negative_number(self):
             
 class TestSplittableIntEquality(tests.IrisTest):
     def test_not_implemented(self):
-        class Terry: pass
+        class Terry:
+            pass
         sin = pp.SplittableInt(0)
         self.assertIs(sin.__eq__(Terry()), NotImplemented)
         self.assertIs(sin.__ne__(Terry()), NotImplemented)
@@ -412,7 +413,8 @@ class Terry: pass
 
 class TestPPDataProxyEquality(tests.IrisTest):
     def test_not_implemented(self):
-        class Terry: pass
+        class Terry:
+            pass
         pox = pp.PPDataProxy("john", "michael", "eric", "graham", "brian",
                              "spam", "beans", "eggs")
         self.assertIs(pox.__eq__(Terry()), NotImplemented)
@@ -421,7 +423,8 @@ class Terry: pass
 
 class TestPPFieldEquality(tests.IrisTest):
     def test_not_implemented(self):
-        class Terry: pass
+        class Terry:
+            pass
         pox = pp.PPField3()
         self.assertIs(pox.__eq__(Terry()), NotImplemented)
         self.assertIs(pox.__ne__(Terry()), NotImplemented)

From bd33a9c451d236d2c56bce9e738bcee7530e580e Mon Sep 17 00:00:00 2001
From: "stephen.worsley" <stephen.worsley@metoffice.gov.uk>
Date: Thu, 7 Nov 2019 13:27:39 +0000
Subject: [PATCH 3/3] remove object from classes with multiple arguments

---
 lib/iris/coord_systems.py                      | 2 +-
 lib/iris/cube.py                               | 2 +-
 lib/iris/fileformats/cf.py                     | 4 ++--
 lib/iris/fileformats/pp.py                     | 2 +-
 lib/iris/palette.py                            | 2 +-
 lib/iris/tests/unit/analysis/maths/__init__.py | 6 +++---
 lib/iris/tests/unit/merge/test_ProtoCube.py    | 2 +-
 lib/iris/tests/unit/tests/test_IrisTest.py     | 2 +-
 tools/translator/__init__.py                   | 2 +-
 9 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/lib/iris/coord_systems.py b/lib/iris/coord_systems.py
index 8e2e87ea2c..78a05b96a8 100644
--- a/lib/iris/coord_systems.py
+++ b/lib/iris/coord_systems.py
@@ -16,7 +16,7 @@
 import cartopy.crs as ccrs
 
 
-class CoordSystem(object, metaclass=ABCMeta):
+class CoordSystem(metaclass=ABCMeta):
     """
     Abstract base class for coordinate systems.
 
diff --git a/lib/iris/cube.py b/lib/iris/cube.py
index 7e4f716219..8a05136479 100644
--- a/lib/iris/cube.py
+++ b/lib/iris/cube.py
@@ -3963,7 +3963,7 @@ def regrid(self, grid, scheme):
         return regridder(self)
 
 
-class ClassDict(MutableMapping, object):
+class ClassDict(MutableMapping):
     """
     A mapping that stores objects keyed on their superclasses and their names.
 
diff --git a/lib/iris/fileformats/cf.py b/lib/iris/fileformats/cf.py
index 3d3cde8896..0c0d96162c 100644
--- a/lib/iris/fileformats/cf.py
+++ b/lib/iris/fileformats/cf.py
@@ -63,7 +63,7 @@ def _is_str_dtype(var):
 
 
 ################################################################################
-class CFVariable(object, metaclass=ABCMeta):
+class CFVariable(metaclass=ABCMeta):
     """Abstract base class wrapper for a CF-netCDF variable."""
 
     #: Name of the netCDF variable attribute that identifies this
@@ -787,7 +787,7 @@ def identify(cls, variables, ignore=None, target=None, warn=True):
 
 
 ################################################################################
-class CFGroup(MutableMapping, object):
+class CFGroup(MutableMapping):
     """
     Represents a collection of 'NetCDF Climate and Forecast (CF) Metadata
     Conventions' variables and netCDF global attributes.
diff --git a/lib/iris/fileformats/pp.py b/lib/iris/fileformats/pp.py
index ddb64a1cda..928da1e795 100644
--- a/lib/iris/fileformats/pp.py
+++ b/lib/iris/fileformats/pp.py
@@ -750,7 +750,7 @@ def _pp_attribute_names(header_defn):
     return normal_headers + special_headers + extra_data + special_attributes
 
 
-class PPField(object, metaclass=abc.ABCMeta):
+class PPField(metaclass=abc.ABCMeta):
     """
     A generic class for PP fields - not specific to a particular
     header release number.
diff --git a/lib/iris/palette.py b/lib/iris/palette.py
index edbbe80883..dc113c93e7 100644
--- a/lib/iris/palette.py
+++ b/lib/iris/palette.py
@@ -156,7 +156,7 @@ def wrapper_func(*args, **kwargs):
     return wrapper_func
 
 
-class SymmetricNormalize(mpl_colors.Normalize, object):
+class SymmetricNormalize(mpl_colors.Normalize):
     """
     Provides a symmetric normalization class around a given pivot point.
     """
diff --git a/lib/iris/tests/unit/analysis/maths/__init__.py b/lib/iris/tests/unit/analysis/maths/__init__.py
index 00f9b7058e..83ac628e82 100644
--- a/lib/iris/tests/unit/analysis/maths/__init__.py
+++ b/lib/iris/tests/unit/analysis/maths/__init__.py
@@ -18,7 +18,7 @@
 import iris.tests as tests
 
 
-class CubeArithmeticBroadcastingTestMixin(object, metaclass=ABCMeta):
+class CubeArithmeticBroadcastingTestMixin(metaclass=ABCMeta):
     # A framework for testing the broadcasting behaviour of the various cube
     # arithmetic operations.  (A test for each operation inherits this).
     @abstractproperty
@@ -107,7 +107,7 @@ def test_slice(self):
                                   err_msg=msg.format(dim))
 
 
-class CubeArithmeticMaskingTestMixin(object, metaclass=ABCMeta):
+class CubeArithmeticMaskingTestMixin(metaclass=ABCMeta):
     # A framework for testing the mask handling behaviour of the various cube
     # arithmetic operations.  (A test for each operation inherits this).
     @abstractproperty
@@ -182,7 +182,7 @@ def SetUpReversed(self):
         return reversed1, reversed2
 
 
-class CubeArithmeticMaskedConstantTestMixin(object, metaclass=ABCMeta):
+class CubeArithmeticMaskedConstantTestMixin(metaclass=ABCMeta):
 
     def test_masked_constant_in_place(self):
         # Cube in_place arithmetic operation.
diff --git a/lib/iris/tests/unit/merge/test_ProtoCube.py b/lib/iris/tests/unit/merge/test_ProtoCube.py
index 1cdca4080d..b91eb8b471 100644
--- a/lib/iris/tests/unit/merge/test_ProtoCube.py
+++ b/lib/iris/tests/unit/merge/test_ProtoCube.py
@@ -29,7 +29,7 @@ def example_cube():
                           units='K', attributes={'mint': 'thin'})
 
 
-class Mixin_register(object, metaclass=abc.ABCMeta):
+class Mixin_register(metaclass=abc.ABCMeta):
     @property
     def cube1(self):
         return example_cube()
diff --git a/lib/iris/tests/unit/tests/test_IrisTest.py b/lib/iris/tests/unit/tests/test_IrisTest.py
index b545158eb0..561e6be884 100644
--- a/lib/iris/tests/unit/tests/test_IrisTest.py
+++ b/lib/iris/tests/unit/tests/test_IrisTest.py
@@ -14,7 +14,7 @@
 import numpy as np
 
 
-class _MaskedArrayEquality(object, metaclass=ABCMeta):
+class _MaskedArrayEquality(metaclass=ABCMeta):
     def setUp(self):
         self.arr1 = np.ma.array([1, 2, 3, 4], mask=[False, True, True, False])
         self.arr2 = np.ma.array([1, 3, 2, 4], mask=[False, True, True, False])
diff --git a/tools/translator/__init__.py b/tools/translator/__init__.py
index 254ddd518f..5d2548f4a7 100644
--- a/tools/translator/__init__.py
+++ b/tools/translator/__init__.py
@@ -85,7 +85,7 @@ def encode(self, fuseki_process):
                                         self.targetmsg.format(**self.targetid))
 
 
-class Mappings(object, metaclass=ABCMeta):
+class Mappings(metaclass=ABCMeta):
     """
     Abstract base class to support the encoding of specific metarelate
     mapping translations.