ifcopenshell.settings.unpack_non_aggregate_inverses

src/ifcopenshell-python/ifcopenshell/entity_instance.py

@@ -29,6 +29,7 @@ import operator
 import functools
 
 from . import ifcopenshell_wrapper
+from . import settings
 
 try:
     import logging
@@ -135,9 +136,21 @@ class entity_instance(object):
                     self.wrapped_data.get_argument(idx), self.wrapped_data.file
                 )
         elif attr_cat == INVERSE:
-            return entity_instance.wrap_value(
+            vs = entity_instance.wrap_value(
                 self.wrapped_data.get_inverse(name), self.wrapped_data.file
             )
+            if settings.unpack_non_aggregate_inverses:
+                schema_name = self.wrapped_data.is_a(True).split(".")[0]
+                ent = ifcopenshell_wrapper.schema_by_name(schema_name).declaration_by_name(
+                    self.is_a()
+                )
+                inv = [i for i in ent.all_inverse_attributes() if i.name() == name][0]
+                if (inv.bound1(), inv.bound2()) == (-1, -1):
+                    if vs:
+                        vs = vs[0]
+                    else:
+                        vs = None
+            return vs
 
         # derived attribute perhaps?
         schema_name = self.wrapped_data.is_a(True).split(".")[0]

src/ifcopenshell-python/ifcopenshell/settings.py

@@ -0,0 +1,36 @@
+# IfcOpenShell - IFC toolkit and geometry engine
+# Copyright (C) 2021 Thomas Krijnen <thomas@aecgeeks.com>
+#
+# This file is part of IfcOpenShell.
+#
+# IfcOpenShell is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# IfcOpenShell is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
+
+"""
+When true return inverses without an aggregate specifier as a single
+element or None. Example:
+
+>>> import ifcopenshell
+>>> f = ifcopenshell.file(schema='ifc2x3')
+>>> f.createIfcGroup()
+#1=IfcGroup($,$,$,$,$)
+>>> f.createIfcRelAssignsToGroup(RelatingGroup=f[1])
+#2=IfcRelAssignsToGroup($,$,$,$,$,$,#1)
+>>> f[1].IsGroupedBy
+(#2=IfcRelAssignsToGroup($,$,$,$,$,$,#1),)
+>>> ifcopenshell.settings.unpack_non_aggregate_inverses = True
+>>> f[1].IsGroupedBy
+#2=IfcRelAssignsToGroup($,$,$,$,$,$,#1)
+"""
+
+unpack_non_aggregate_inverses = False