Add cache reset for when G._node is changed (#5894)

1 files changed, 23 insertions, 0 deletions

diff --git a/networkx/classes/graph.py b/networkx/classes/graph.py
index ebbc8b53..47d5f81d 100644
--- a/networkx/classes/graph.py
+++ b/networkx/classes/graph.py
@@ -41,6 +41,28 @@ class _CachedPropertyResetterAdj:
             del od["adj"]
 
 
+class _CachedPropertyResetterNode:
+    """Data Descriptor class for _node that resets ``nodes`` cached_property when needed
+
+    This assumes that the ``cached_property`` ``G.node`` should be reset whenever
+    ``G._node`` is set to a new value.
+
+    This object sits on a class and ensures that any instance of that
+    class clears its cached property "nodes" whenever the underlying
+    instance attribute "_node" is set to a new object. It only affects
+    the set process of the obj._adj attribute. All get/del operations
+    act as they normally would.
+
+    For info on Data Descriptors see: https://docs.python.org/3/howto/descriptor.html
+    """
+
+    def __set__(self, obj, value):
+        od = obj.__dict__
+        od["_node"] = value
+        if "nodes" in od:
+            del od["nodes"]
+
+
 class Graph:
     """
     Base class for undirected graphs.
@@ -282,6 +304,7 @@ class Graph:
     """
 
     _adj = _CachedPropertyResetterAdj()
+    _node = _CachedPropertyResetterNode()
 
     node_dict_factory = dict
     node_attr_dict_factory = dict