Implement faster addition of many vertices

doc/quickstart.rst

@@ -122,12 +122,13 @@ vertex of an edge, respectively.
 
 The :meth:`~graph_tool.Graph.add_vertex` method also accepts an optional
 parameter which specifies the number of vertices to create. If this
-value is greater than 1, it returns a list of vertex descriptors:
+value is greater than 1, it returns an iterator on the added vertex
+descriptors:
 
 .. doctest::
 
    >>> vlist = g.add_vertex(10)
-   >>> print(len(vlist))
+   >>> print(len(list(vlist)))
    10
 
 Edges and vertices can also be removed at any time with the

src/graph/graph_python_interface.cc

@@ -126,9 +126,16 @@ python::object get_edges(python::object g)
     return iter;
 }
 
-python::object add_vertex(python::object g)
+python::object add_vertex(python::object g, size_t n)
 {
     GraphInterface& gi = python::extract<GraphInterface&>(g().attr("_Graph__graph"));
+
+    if (n > 1)
+    {
+        for (size_t i = 0; i < n; ++i)
+            add_vertex(gi.GetGraph());
+        return python::object();
+    }
     return python::object(PythonVertex(g, add_vertex(gi.GetGraph())));
 }
 

src/graph_tool/__init__.py

@@ -1091,18 +1091,15 @@ class Graph(object):
 
     def add_vertex(self, n=1):
         """Add a vertex to the graph, and return it. If ``n > 1``, ``n``
-        vertices are inserted and a list is returned."""
+        vertices are inserted and an iterator over the new vertices is returned."""
         self.__check_perms("add_vertex")
-        vlist = []
-        vfilt = self.get_vertex_filter()
-        for i in range(n):
-            v = libcore.add_vertex(weakref.ref(self))
-            if vfilt[0] is not None:
-                vfilt[0][v] = not vfilt[1]
-            vlist.append(v)
-        if n == 1:
-            return vlist[0]
-        return vlist
+        v = libcore.add_vertex(weakref.ref(self), n)
+
+        if n <= 1:
+            return v
+        else:
+            pos = self.num_vertices() - n
+            return (self.vertex(i) for i in xrange(pos, pos + n))
 
     def remove_vertex(self, vertex):
         """Remove a vertex from the graph."""