modified docs

Author: pratikgl

pydatastructs/graphs/adjacency_list.py

@@ -52,29 +52,24 @@ def remove_vertex(self, name):
                 node_obj.adjacent.remove(name)
 
     def add_edge(self, source, target, cost=None):
+        error_msg = "Vertex %s is not present in the graph. \
+                    Call Graph.add_vertex() to add a new \
+                    vertex. Graph.add_edge is only responsible \
+                    for adding edges and it will not add new \
+                    vertices on its own. This is done to maintain \
+                    clear separation between the functionality of \
+                    the two methods."
         if not hasattr(self, source):
-            raise ValueError("Vertex %s is not present in the graph."
-                            " Call Graph.add_vertex() to add a new"
-                            " vertex. Graph.add_edge is only responsible"
-                            " for adding edges and it will not add new"
-                            " vertices on its own. This is done to maintain"
-                            " clear separation between the functionality of"
-                            " the two methods." %(source))
-        elif not hasattr(self, target):
-            raise ValueError("Vertex %s is not present in the graph."
-                            " Call Graph.add_vertex() to add a new"
-                            " vertex. Graph.add_edge is only responsible"
-                            " for adding edges and it will not add new"
-                            " vertices on its own. This is done to maintain"
-                            " clear separation between the functionality of"
-                            " the two methods." %(target))
-        else:
-            source, target = self.__getattribute__(source), \
-                self.__getattribute__(target)
-            source.add_adjacent_node(target.name)
-            if cost is not None:
-                self.edge_weights[source.name + "_" + target.name] = \
-                    GraphEdge(source, target, cost)
+            raise ValueError(error_msg %(source))
+        if not hasattr(self, target):
+            raise ValueError(error_msg %(target))
+
+        source, target = self.__getattribute__(source), \
+            self.__getattribute__(target)
+        source.add_adjacent_node(target.name)
+        if cost is not None:
+            self.edge_weights[source.name + "_" + target.name] = \
+                GraphEdge(source, target, cost)
 
     def get_edge(self, source, target):
         return self.edge_weights.get(

pydatastructs/graphs/graph.py

@@ -52,9 +52,13 @@ class Graph(object):
 
     Note
     ====
+
     Steps to create a graph:
+
     1. Create nodes (AdjacencyListGraphNode or AdjacencyListMatrixNode)
+
     2. Add nodes to the graph
+
     3. Add edges b/w these nodes
 
     """