diff --git a/pygsti/baseobjs/label.py b/pygsti/baseobjs/label.py
index c0e6102b9..172d63274 100644
--- a/pygsti/baseobjs/label.py
+++ b/pygsti/baseobjs/label.py
@@ -187,6 +187,15 @@ def expand_subcircuits(self):
             :class:`CircuitLabel` objects).
         """
         return (self,)  # most labels just expand to themselves
+    
+    @property
+    def is_simple(self):
+        """
+        Whether this is a "simple" (opaque w/a true name, from a circuit perspective) label or not.    
+        """
+
+        return self.IS_SIMPLE
+
 
 
 class LabelTup(Label, tuple):
@@ -200,7 +209,7 @@ class LabelTup(Label, tuple):
 
     #flag used in certain Circuit subroutines
     #Whether this is a "simple" (opaque w/a true name, from a circuit perspective) label or not.
-    is_simple= True
+    IS_SIMPLE = True
 
     @classmethod
     def init(cls, name, state_space_labels):
@@ -436,7 +445,7 @@ class LabelTupWithTime(Label, tuple):
 
     #flag used in certain Circuit subroutines
     #Whether this is a "simple" (opaque w/a true name, from a circuit perspective) label or not.
-    is_simple= True
+    IS_SIMPLE = True
 
     @classmethod
     def init(cls, name, state_space_labels, time=0.0):
@@ -680,7 +689,7 @@ class LabelStr(Label, str):
 
     #flag used in certain Circuit subroutines
     #Whether this is a "simple" (opaque w/a true name, from a circuit perspective) label or not.
-    is_simple= True
+    IS_SIMPLE = True
 
     @classmethod
     def init(cls, name, time=0.0):
@@ -853,7 +862,7 @@ class LabelTupTup(Label, tuple):
 
     #flag used in certain Circuit subroutines
     #Whether this is a "simple" (opaque w/a true name, from a circuit perspective) label or not.
-    is_simple= False
+    IS_SIMPLE = False
 
     @classmethod
     def init(cls, tup_of_tups):
@@ -1108,7 +1117,7 @@ class LabelTupTupWithTime(Label, tuple):
 
     #flag used in certain Circuit subroutines
     #Whether this is a "simple" (opaque w/a true name, from a circuit perspective) label or not.
-    is_simple= False
+    IS_SIMPLE = False
 
     @classmethod
     def init(cls, tup_of_tups, time=None):
@@ -1369,7 +1378,7 @@ class CircuitLabel(Label, tuple):
 
     #flag used in certain Circuit subroutines
     #Whether this is a "simple" (opaque w/a true name, from a circuit perspective) label or not.
-    is_simple= True
+    IS_SIMPLE = True
 
     def __new__(cls, name, tup_of_layers, state_space_labels, reps=1, time=None):
         # Note: may need default args for all but 1st for pickling!
@@ -1641,7 +1650,7 @@ class LabelTupWithArgs(Label, tuple):
 
     #flag used in certain Circuit subroutines
     #Whether this is a "simple" (opaque w/a true name, from a circuit perspective) label or not.
-    is_simple= True
+    IS_SIMPLE = True
 
     @classmethod
     def init(cls, name, state_space_labels, time=0.0, args=()):
@@ -1909,7 +1918,7 @@ class LabelTupTupWithArgs(Label, tuple):
 
     #flag used in certain Circuit subroutines
     #Whether this is a "simple" (opaque w/a true name, from a circuit perspective) label or not.
-    is_simple= False
+    IS_SIMPLE = False
 
     @classmethod
     def init(cls, tup_of_tups, time=None, args=()):
diff --git a/pygsti/circuits/circuit.py b/pygsti/circuits/circuit.py
index 56c571e94..6764d322c 100644
--- a/pygsti/circuits/circuit.py
+++ b/pygsti/circuits/circuit.py
@@ -96,7 +96,7 @@ def _label_to_nested_lists_of_simple_labels(lbl, default_sslbls=None, always_ret
     """ Convert lbl into nested lists of *simple* labels """
     if not isinstance(lbl, _Label):  # if not a Label, make into a label,
         lbl = _Label(lbl)  # e.g. a string or list/tuple of labels, etc.
-    if lbl.is_simple:  # a *simple* label - the elements of our lists
+    if lbl.IS_SIMPLE:  # a *simple* label - the elements of our lists
         if lbl.sslbls is None and default_sslbls is not None:
             lbl = _Label(lbl.name, default_sslbls)
         return [lbl] if always_return_list else lbl
@@ -120,7 +120,7 @@ def _accumulate_explicit_sslbls(obj):
     """
     ret = set()
     if isinstance(obj, _Label):
-        if not obj.is_simple:
+        if not obj.IS_SIMPLE:
             for lbl in obj.components:
                 ret.update(_accumulate_explicit_sslbls(lbl))
         else:  # a simple label
@@ -1027,7 +1027,7 @@ def copy(self, editable='auto'):
         if editable:
             if self._static:
                 #static and editable circuits have different conventions for _labels.
-                editable_labels =[[lbl] if lbl.is_simple else list(lbl.components) for lbl in self._labels]
+                editable_labels =[[lbl] if lbl.IS_SIMPLE else list(lbl.components) for lbl in self._labels]
                 return ret._copy_init(editable_labels, self._line_labels, editable, 
                                       self._name, self._str, self._occurrence_id, 
                                       self._compilable_layer_indices_tup)
@@ -1107,7 +1107,7 @@ def _layer_components(self, ilayer):
         """ Get the components of the `ilayer`-th layer as a list/tuple. """
         #(works for static and non-static Circuits)
         if self._static:
-            if self._labels[ilayer].is_simple: return [self._labels[ilayer]]
+            if self._labels[ilayer].IS_SIMPLE: return [self._labels[ilayer]]
             else: return self._labels[ilayer].components
         else:
             return self._labels[ilayer] if isinstance(self._labels[ilayer], list) \
@@ -2762,7 +2762,7 @@ def mapper_func(gatename): return mapper.get(gatename, None) \
 
         def map_names(obj):  # obj is either a simple label or a list
             if isinstance(obj, _Label):
-                if obj.is_simple:  # *simple* label
+                if obj.IS_SIMPLE:  # *simple* label
                     new_name = mapper_func(obj.name)
                     newobj = _Label(new_name, obj.sslbls) \
                         if (new_name is not None) else obj
@@ -3401,7 +3401,7 @@ def size(self):
         #TODO HERE -update from here down b/c of sub-circuit blocks
         if self._static:
             def size(lbl):  # obj a Label, perhaps compound
-                if lbl.is_simple:  # a simple label
+                if lbl.IS_SIMPLE:  # a simple label
                     return len(lbl.sslbls) if (lbl.sslbls is not None) else len(self._line_labels)
                 else:
                     return sum([size(sublbl) for sublbl in lbl.components])
@@ -3456,7 +3456,7 @@ def num_nq_gates(self, nq):
         """
         if self._static:
             def cnt(lbl):  # obj a Label, perhaps compound
-                if lbl.is_simple:  # a simple label
+                if lbl.IS_SIMPLE:  # a simple label
                     return 1 if (lbl.sslbls is not None) and (len(lbl.sslbls) == nq) else 0
                 else:
                     return sum([cnt(sublbl) for sublbl in lbl.components])
@@ -3484,7 +3484,7 @@ def num_multiq_gates(self):
         """
         if self._static:
             def cnt(lbl):  # obj a Label, perhaps compound
-                if lbl.is_simple:  # a simple label
+                if lbl.IS_SIMPLE:  # a simple label
                     return 1 if (lbl.sslbls is not None) and (len(lbl.sslbls) >= 2) else 0
                 else:
                     return sum([cnt(sublbl) for sublbl in lbl.components])
@@ -3507,7 +3507,7 @@ def _togrid(self, identity_name):
             for layercomp in self._layer_components(ilayer):
                 if isinstance(layercomp, _Label):
                     comp_label = layercomp
-                    if layercomp.is_simple:
+                    if layercomp.IS_SIMPLE:
                         comp_sslbls = layercomp.sslbls
                     else:
                         #We can't intelligently flatten compound labels that occur within a layer-label yet...