Consistent use of ABC instead of ABCMeta where possible

openmc/data/angle_energy.py

@@ -1,10 +1,10 @@
-from abc import ABCMeta, abstractmethod
+from abc import ABC, abstractmethod
 
 import openmc.data
 from openmc.mixin import EqualityMixin
 
 
-class AngleEnergy(EqualityMixin, metaclass=ABCMeta):
+class AngleEnergy(EqualityMixin, ABC):
     """Distribution in angle and energy of a secondary particle."""
     @abstractmethod
     def to_hdf5(self, group):

openmc/data/energy_distribution.py

@@ -1,4 +1,4 @@
-from abc import ABCMeta, abstractmethod
+from abc import ABC, abstractmethod
 from collections.abc import Iterable
 from numbers import Integral, Real
 from warnings import warn
@@ -13,7 +13,7 @@ from .data import EV_PER_MEV
 from .endf import get_tab1_record, get_tab2_record
 
 
-class EnergyDistribution(EqualityMixin, metaclass=ABCMeta):
+class EnergyDistribution(EqualityMixin, ABC):
     """Abstract superclass for all energy distributions."""
     def __init__(self):
         pass

openmc/data/function.py

@@ -1,4 +1,4 @@
-from abc import ABCMeta, abstractmethod
+from abc import ABC, abstractmethod
 from collections.abc import Iterable, Callable
 from functools import reduce
 from itertools import zip_longest
@@ -56,7 +56,7 @@ def sum_functions(funcs):
         return Polynomial(coeffs)
 
 
-class Function1D(EqualityMixin, metaclass=ABCMeta):
+class Function1D(EqualityMixin, ABC):
     """A function of one independent variable with HDF5 support."""
     @abstractmethod
     def __call__(self): pass

openmc/lattice.py

@@ -1,4 +1,4 @@
-from abc import ABCMeta
+from abc import ABC
 from collections import OrderedDict
 from collections.abc import Iterable
 from copy import deepcopy
@@ -15,7 +15,7 @@ from openmc._xml import get_text
 from openmc.mixin import IDManagerMixin
 
 
-class Lattice(IDManagerMixin, metaclass=ABCMeta):
+class Lattice(IDManagerMixin, ABC):
     """A repeating structure wherein each element is a universe.
 
     Parameters

openmc/mesh.py

@@ -1,4 +1,4 @@
-from abc import ABCMeta
+from abc import ABC
 from collections.abc import Iterable
 from numbers import Real, Integral
 from xml.etree import ElementTree as ET
@@ -13,7 +13,7 @@ from openmc.mixin import IDManagerMixin
 from openmc.surface import _BOUNDARY_TYPES
 
 
-class MeshBase(IDManagerMixin, metaclass=ABCMeta):
+class MeshBase(IDManagerMixin, ABC):
     """A mesh that partitions geometry for tallying purposes.
 
     Parameters

openmc/mgxs/mgxs.py

@@ -3,7 +3,6 @@ from numbers import Integral
 import warnings
 import os
 import copy
-from abc import ABCMeta
 
 import numpy as np
 import h5py
@@ -128,7 +127,7 @@ def _df_column_convert_to_bin(df, current_name, new_name, values_to_bin,
     df.rename(columns={current_name: new_name}, inplace=True)
 
 
-class MGXS(metaclass=ABCMeta):
+class MGXS:
     """An abstract multi-group cross section for some energy group structure
     within some spatial domain.
 

openmc/model/triso.py

@@ -2,7 +2,7 @@ import copy
 import warnings
 import itertools
 import random
-from abc import ABCMeta, abstractproperty, abstractmethod
+from abc import ABC, abstractproperty, abstractmethod
 from collections import Counter, defaultdict
 from collections.abc import Iterable
 from heapq import heappush, heappop
@@ -100,7 +100,7 @@ class TRISO(openmc.Cell):
                 k_min:k_max+1, j_min:j_max+1, i_min:i_max+1]))
 
 
-class _Container(metaclass=ABCMeta):
+class _Container(ABC):
     """Container in which to pack spheres.
 
     Parameters

openmc/region.py

@@ -1,4 +1,4 @@
-from abc import ABCMeta, abstractmethod
+from abc import ABC, abstractmethod
 from collections import OrderedDict
 from collections.abc import MutableSequence
 from copy import deepcopy
@@ -8,7 +8,7 @@ import numpy as np
 from openmc.checkvalue import check_type
 
 
-class Region(metaclass=ABCMeta):
+class Region(ABC):
     """Region of space that can be assigned to a cell.
 
     Region is an abstract base class that is inherited by

openmc/stats/multivariate.py

@@ -1,4 +1,4 @@
-from abc import ABCMeta, abstractmethod
+from abc import ABC, abstractmethod
 from collections.abc import Iterable
 from math import pi
 from numbers import Real
@@ -11,7 +11,7 @@ from openmc._xml import get_text
 from openmc.stats.univariate import Univariate, Uniform
 
 
-class UnitSphere(metaclass=ABCMeta):
+class UnitSphere(ABC):
     """Distribution of points on the unit sphere.
 
     This abstract class is used for angular distributions, since a direction is
@@ -251,7 +251,7 @@ class Monodirectional(UnitSphere):
         return monodirectional
 
 
-class Spatial(metaclass=ABCMeta):
+class Spatial(ABC):
     """Distribution of locations in three-dimensional Euclidean space.
 
     Classes derived from this abstract class can be used for spatial

openmc/stats/univariate.py

@@ -1,4 +1,4 @@
-from abc import ABCMeta, abstractmethod
+from abc import ABC, abstractmethod
 from collections.abc import Iterable
 from numbers import Real
 from xml.etree import ElementTree as ET
@@ -14,7 +14,7 @@ _INTERPOLATION_SCHEMES = ['histogram', 'linear-linear', 'linear-log',
                           'log-linear', 'log-log']
 
 
-class Univariate(EqualityMixin, metaclass=ABCMeta):
+class Univariate(EqualityMixin, ABC):
     """Probability distribution of a single random variable.
 
     The Univariate class is an abstract class that can be derived to implement a

openmc/surface.py

@@ -1,4 +1,4 @@
-from abc import ABCMeta, abstractmethod
+from abc import ABC, abstractmethod
 from collections import OrderedDict
 from collections.abc import Iterable
 from copy import deepcopy
@@ -103,7 +103,7 @@ def get_rotation_matrix(rotation, order='xyz'):
     return R3 @ R2 @ R1
 
 
-class Surface(IDManagerMixin, metaclass=ABCMeta):
+class Surface(IDManagerMixin, ABC):
     """An implicit surface with an associated boundary condition.
 
     An implicit surface is defined as the set of zeros of a function of the
@@ -459,7 +459,7 @@ class Surface(IDManagerMixin, metaclass=ABCMeta):
         return cls(*coeffs, **kwargs)
 
 
-class PlaneMixin(metaclass=ABCMeta):
+class PlaneMixin:
     """A Plane mixin class for all operations on order 1 surfaces"""
     def __init__(self, **kwargs):
         super().__init__(**kwargs)
@@ -918,7 +918,7 @@ class ZPlane(PlaneMixin, Surface):
         return point[2] - self.z0
 
 
-class QuadricMixin(metaclass=ABCMeta):
+class QuadricMixin:
     """A Mixin class implementing common functionality for quadric surfaces"""
 
     @property