refactor load/save functions

Use streams instead of filename.
Move load/write functions if modules where logical.

voronoi.py

@@ -4,6 +4,7 @@
 from utils import tour,LOG,LOGN,x,y
 import triangulation
 import geometry
+import graph
 
 def nodes( triangles ):
     """Compute the locations of the centers of all the circumscribed circles of the given triangles"""
@@ -68,17 +69,6 @@ def dual( triangles ):
     return graph
 
 
-def edges_of( graph ):
-    # edges = set()
-    edges = []
-    for k in graph:
-        for n in graph[k]:
-            if k != n and (k,n) not in edges and (n,k) not in edges:
-                # edges.add( (k,n) )
-                edges.append( (k,n) )
-    return edges
-
-
 def merge_nodes( graph, n0, n1, n2 ):
     """Merge n0 and n1 nodes as n2 within the given graph."""
 
@@ -179,7 +169,7 @@ if __name__ == "__main__":
     delaunay_edges = triangulation.edges_of( triangles )
 
     voronoi_graph = dual( triangles )
-    voronoi_edges = edges_of( voronoi_graph )
+    voronoi_edges = graph.edges_of( voronoi_graph )
     print voronoi_edges
 
     ax = fig.add_subplot(111)