adjacency list in python

python/adjacency_list.py

@@ -0,0 +1,26 @@
+import sys
+
+graph = {}
+
+def build_graph(graph_file):
+    with open(graph_file) as f:
+        for l in f.readlines():
+            start, end = l.strip('\n').split(',') 
+            arc_list = graph.get(start, [])
+            arc_list.append(end)
+            if start not in graph:
+                graph[start] = arc_list
+
+def arc_in(graph, start, end):
+    return end in graph.get(start,[])
+
+def edge_in(graph, first, second):
+    return arc_in(graph, first, second) and arc_in(graph, second, first)
+
+if __name__ == '__main__':
+    build_graph(sys.argv[1])
+
+    print graph
+    print edge_in(graph, '1','3')
+    print edge_in(graph, '1','8')
+    print arc_in(graph, '1','8')

python/graph1.dat

@@ -0,0 +1,7 @@
+1,3
+3,1
+1,8
+2,3
+2,4
+2,6
+3,7