fix: account for idx=0

Author: maximelucas

xgi/core/dihypergraph.py

@@ -581,7 +581,7 @@ def add_edge(self, members, idx=None, **attr):
         self._edge_attr[uid] = self._edge_attr_dict_factory()
         self._edge_attr[uid].update(attr)
 
-        if idx:  # set self._edge_uid correctly
+        if idx is not None:  # set self._edge_uid correctly
             update_uid_counter(self, idx)
 
     def add_edges_from(self, ebunch_to_add, **attr):

xgi/core/hypergraph.py

@@ -627,7 +627,7 @@ def add_edge(self, members, idx=None, **attr):
         self._edge_attr[uid] = self._edge_attr_dict_factory()
         self._edge_attr[uid].update(attr)
 
-        if idx:  # set self._edge_uid correctly
+        if idx is not None:  # set self._edge_uid correctly
             update_uid_counter(self, idx)
 
     def add_edges_from(self, ebunch_to_add, **attr):

xgi/core/simplicialcomplex.py

@@ -314,7 +314,7 @@ def add_simplex(self, members, idx=None, **attr):
             warn(f"uid {idx} already exists, cannot add simplex {members}")
             return
 
-        idx = next(self._edge_uid) if not idx else idx
+        idx = next(self._edge_uid) if idx is None else idx
 
         self._add_simplex(members, idx, **attr)