[Python] Remove most weakproxy sentinels

interfaces/cython/cantera/_onedim.pxd

@@ -153,7 +153,6 @@ cdef class Domain1D:
     cdef shared_ptr[CxxDomain1D] _domain
     cdef CxxDomain1D* domain
     cdef _SolutionBase gas
-    cdef object _weakref_proxy
     cdef public pybool have_user_tolerances
 
 cdef class Boundary1D(Domain1D):

interfaces/cython/cantera/_onedim.pyx

@@ -9,23 +9,16 @@ from ._utils cimport stringify, pystr, anymap_to_py
 from ._utils import CanteraError
 from cython.operator import dereference as deref
 
-# Need a pure-python class to store weakrefs to
-class _WeakrefProxy:
-    pass
-
 cdef class Domain1D:
     _domain_type = "none"
     def __cinit__(self, _SolutionBase phase not None, *args, **kwargs):
         self.domain = NULL
 
     def __init__(self, phase, *args, **kwargs):
-        self._weakref_proxy = _WeakrefProxy()
         if self.domain is NULL:
             raise TypeError("Can't instantiate abstract class Domain1D.")
 
         self.gas = phase
-        # Block species from being added to the phase as long as this object exists
-        self.gas._references[self._weakref_proxy] = True
         self.set_default_tolerances()
 
     property phase:
@@ -424,7 +417,6 @@ cdef class ReactingSurface1D(Boundary1D):
     _domain_type = "reacting-surface"
 
     def __init__(self, _SolutionBase phase, name=None):
-        self._weakref_proxy = _WeakrefProxy()
         gas = None
         for val in phase._adjacent.values():
             if val.phase_of_matter == "gas":
@@ -435,8 +427,6 @@ cdef class ReactingSurface1D(Boundary1D):
         super().__init__(gas, name=name)
 
         self.surface = phase
-        # Block species from being added to the phase as long as this object exists
-        self.surface._references[self._weakref_proxy] = True
 
     property phase:
         """

interfaces/cython/cantera/composite.py

@@ -142,6 +142,11 @@ class DustyGas(DustyGasTransport, Kinetics, ThermoPhase):
     __slots__ = ()
 
 
+# A pure-Python class to store weakrefs to
+class _WeakrefProxy:
+    pass
+
+
 class Quantity:
     """
     A class representing a specific quantity of a `Solution`. In addition to the
@@ -382,11 +387,6 @@ for _attr in dir(Solution):
             setattr(Quantity, _attr, _prop(_attr))
 
 
-# A pure-Python class to store weakrefs to
-class _WeakrefProxy:
-    pass
-
-
 class SolutionArray(SolutionArrayBase):
     """
     A class providing a convenient interface for representing many thermodynamic
@@ -583,8 +583,6 @@ class SolutionArray(SolutionArrayBase):
 
     def __init__(self, phase, shape=(0,), states=None, extra=None, meta={}, init=True):
         self._phase = phase
-        self._weakref_proxy = _WeakrefProxy()
-        phase._references[self._weakref_proxy] = True
         if not init:
             return
 

interfaces/cython/cantera/mixture.pxd

@@ -52,5 +52,4 @@ cdef extern from "cantera/equil/MultiPhase.h" namespace "Cantera":
 cdef class Mixture:
     cdef CxxMultiPhase* mix
     cdef list _phases
-    cdef object _weakref_proxy
     cpdef int element_index(self, element) except *

interfaces/cython/cantera/mixture.pyx

@@ -8,10 +8,6 @@ from .solutionbase cimport *
 from .thermo cimport *
 from ._utils cimport *
 
-# Need a pure-python class to store weakrefs to
-class _WeakrefProxy:
-    pass
-
 cdef class Mixture:
     """
 
@@ -44,7 +40,6 @@ cdef class Mixture:
     def __cinit__(self, phases):
         self.mix = new CxxMultiPhase()
         self._phases = []
-        self._weakref_proxy = _WeakrefProxy()
 
         cdef _SolutionBase phase
         if isinstance(phases[0], _SolutionBase):
@@ -53,7 +48,6 @@ cdef class Mixture:
 
         for phase,moles in phases:
             # Block species from being added to the phase as long as this object exists
-            phase._references[self._weakref_proxy] = True
             self.mix.addPhase(phase.thermo, moles)
             self._phases.append(phase)
 

interfaces/cython/cantera/reactor.pxd

@@ -223,7 +223,6 @@ cdef class ReactorBase:
     cdef list _outlets
     cdef list _walls
     cdef list _surfaces
-    cdef object _weakref_proxy
     cdef public dict node_attr
     """
     A dictionary containing draw attributes for the representation of the reactor as a

interfaces/cython/cantera/reactor.pyx

@@ -14,10 +14,6 @@ from .drawnetwork import *
 
 _reactor_counts = _defaultdict(int)
 
-# Need a pure-python class to store weakrefs to
-class _WeakrefProxy:
-    pass
-
 cdef class ReactorBase:
     """
     Common base class for reactors and reservoirs.
@@ -41,8 +37,6 @@ cdef class ReactorBase:
 
     def __init__(self, _SolutionBase contents=None, name=None, *, volume=None,
                  node_attr=None):
-
-        self._weakref_proxy = _WeakrefProxy()
         self._inlets = []
         self._outlets = []
         self._walls = []
@@ -61,8 +55,6 @@ cdef class ReactorBase:
         properties and kinetic rates for this reactor.
         """
         self._thermo = solution
-        # Block species from being added to the phase as long as this object exists
-        self._thermo._references[self._weakref_proxy] = True
         self.rbase.setSolution(solution._base)
 
     property type:

interfaces/cython/cantera/solutionbase.pxd

@@ -122,4 +122,3 @@ cdef class _SolutionBase:
 cdef class SolutionArrayBase:
     cdef shared_ptr[CxxSolutionArray] _base
     cdef CxxSolutionArray* base
-    cdef public object _weakref_proxy

interfaces/cython/cantera/thermo.pyx

@@ -270,10 +270,9 @@ cdef class ThermoPhase(_SolutionBase):
         # In composite objects, the ThermoPhase constructor needs to be called first
         # to prevent instantiation of stand-alone 'Kinetics' or 'Transport' objects.
         # The following is used as a sentinel. After initialization, the _references
-        # object is used to track whether the ThermoPhase is being used by a `Reactor`,
-        # `Domain1D`, or `Mixture` object and to prevent species from being added to the
-        # ThermoPhase if so, since these objects require the number of species to remain
-        # constant.
+        # object is used to track whether the ThermoPhase is being used by other
+        # objects that require the number of species to remain constant and do not
+        # have C++ implementations (e.g. Quantity objects).
         self._references = weakref.WeakKeyDictionary()
         # validate plasma phase
         self._enable_plasma = False
@@ -583,8 +582,7 @@ cdef class ThermoPhase(_SolutionBase):
         """
         if self._references:
             raise CanteraError('Cannot add species to ThermoPhase object because it'
-                ' is being used by another object,\nsuch as a Reactor, Domain1D (flame),'
-                ' SolutionArray, Quantity, or Mixture object.')
+                ' is being used by a Quantity object.')
         self.thermo.addUndefinedElements()
         self.thermo.addSpecies(species._species)
         species._phase = self