Fix: allow graph subclasses to have additional arguments (#8369)

Co-authored-by: Ross Barnowski <rossbar@caltech.edu>

Author: eriknw

networkx/classes/digraph.py

@@ -338,7 +338,7 @@ class DiGraph(Graph):
     # in order to provide a backend that allows class instantiation, this method
     # can be overridden to return your own backend graph class.
     @nx._dispatchable(name="digraph__new__", graphs=None, returns_graph=True)
-    def __new__(cls, incoming_graph_data=None, **attr):
+    def __new__(cls, *args, **kwargs):
         return object.__new__(cls)
 
     def __init__(self, incoming_graph_data=None, **attr):

networkx/classes/graph.py

@@ -343,7 +343,7 @@ def to_undirected_class(self):
     # in order to provide a backend that allows class instantiation, this method
     # can be overridden to return your own backend graph class.
     @nx._dispatchable(name="graph__new__", graphs=None, returns_graph=True)
-    def __new__(cls, incoming_graph_data=None, **attr):
+    def __new__(cls, *args, **kwargs):
         return object.__new__(cls)
 
     def __init__(self, incoming_graph_data=None, **attr):

networkx/classes/multidigraph.py

@@ -306,7 +306,7 @@ class MultiDiGraph(MultiGraph, DiGraph):
     # in order to provide a backend that allows class instantiation, this method
     # can be overridden to return your own backend graph class.
     @nx._dispatchable(name="multidigraph__new__", graphs=None, returns_graph=True)
-    def __new__(cls, incoming_graph_data=None, multigraph_input=None, **attr):
+    def __new__(cls, *args, **kwargs):
         return object.__new__(cls)
 
     def __init__(self, incoming_graph_data=None, multigraph_input=None, **attr):

networkx/classes/multigraph.py

@@ -314,7 +314,7 @@ def to_undirected_class(self):
     # in order to provide a backend that allows class instantiation, this method
     # can be overridden to return your own backend graph class.
     @nx._dispatchable(name="multigraph__new__", graphs=None, returns_graph=True)
-    def __new__(cls, incoming_graph_data=None, multigraph_input=None, **attr):
+    def __new__(cls, *args, **kwargs):
         return object.__new__(cls)
 
     def __init__(self, incoming_graph_data=None, multigraph_input=None, **attr):

networkx/classes/tests/test_graph.py

@@ -925,3 +925,26 @@ def test_graph_attr_dict(self):
 
         """
         assert self.G.graph is self.H.graph
+
+
+def test_graph_new_extra_args():
+    """Test that subclasses can accept additional arguments.
+
+    See: https://github.com/networkx/networkx/issues/8367
+    """
+
+    class MyGraph(nx.Graph):
+        def __init__(self, incoming_graph_data=None, extra_arg=None, **attr):
+            super().__init__(incoming_graph_data, **attr)
+            self.extra_arg = extra_arg
+
+    G = MyGraph(extra_arg="extra arg")
+    assert G.extra_arg == "extra arg"
+
+    G = MyGraph([], "extra arg")
+    assert G.extra_arg == "extra arg"
+
+    G = MyGraph([(0, 1)], extra_arg="foo", name="bar")
+    assert G.extra_arg == "foo"
+    assert G.graph["name"] == "bar"
+    assert nx.utils.edges_equal(G.edges, [(0, 1)])