Add exception class NodeNotFound

3 files changed, 21 insertions, 16 deletions

diff --git a/networkx/algorithms/simple_paths.py b/networkx/algorithms/simple_paths.py
index 21fd99ca..f755f269 100644
--- a/networkx/algorithms/simple_paths.py
+++ b/networkx/algorithms/simple_paths.py
@@ -77,9 +77,9 @@ def all_simple_paths(G, source, target, cutoff=None):
     all_shortest_paths, shortest_path
     """
     if source not in G:
-        raise nx.NetworkXError('source node %s not in graph'%source)
+        raise nx.NodeNotFound('source node %s not in graph'%source)
     if target not in G:
-        raise nx.NetworkXError('target node %s not in graph'%target)
+        raise nx.NodeNotFound('target node %s not in graph'%target)
     if cutoff is None:
         cutoff = len(G)-1
     if G.is_multigraph():
@@ -216,10 +216,10 @@ def shortest_simple_paths(G, source, target, weight=None):
 
     """
     if source not in G:
-        raise nx.NetworkXError('source node %s not in graph' % source)
+        raise nx.NodeNotFound('source node %s not in graph' % source)
 
     if target not in G:
-        raise nx.NetworkXError('target node %s not in graph' % target)
+        raise nx.NodeNotFound('target node %s not in graph' % target)
 
     if weight is None:
         length_func = len
@@ -295,7 +295,7 @@ def _bidirectional_shortest_path(G, source, target,
     """Return the shortest path between source and target ignoring
        nodes and edges in the containers ignore_nodes and ignore_edges.
 
-    This is a custom modification of the standard bidirectional shortest 
+    This is a custom modification of the standard bidirectional shortest
     path implementation at networkx.algorithms.unweighted
 
     Parameters
@@ -315,7 +315,7 @@ def _bidirectional_shortest_path(G, source, target,
        edges to ignore, optional
 
     weight : None
-       This function accepts a weight argument for convinience of 
+       This function accepts a weight argument for convinience of
        shortest_simple_paths function. It will be ignored.
 
     Returns
@@ -454,7 +454,7 @@ def _bidirectional_dijkstra(G, source, target, weight='weight',
     """Dijkstra's algorithm for shortest paths using bidirectional search.
 
     This function returns the shortest path between source and target
-    ignoring nodes and edges in the containers ignore_nodes and 
+    ignoring nodes and edges in the containers ignore_nodes and
     ignore_edges.
 
     This is a custom modification of the standard Dijkstra bidirectional
diff --git a/networkx/algorithms/tests/test_simple_paths.py b/networkx/algorithms/tests/test_simple_paths.py
index c068c70a..01e42c52 100644
--- a/networkx/algorithms/tests/test_simple_paths.py
+++ b/networkx/algorithms/tests/test_simple_paths.py
@@ -1,6 +1,6 @@
 #!/usr/bin/env python
 import random
-from nose.tools import *
+from nose.tools import assert_equal, assert_raises, assert_true, raises
 
 import networkx as nx
 from networkx import convert_node_labels_to_integers as cnlti
@@ -67,13 +67,13 @@ def test_cutoff_zero():
     paths = nx.all_simple_paths(nx.MultiGraph(G),0,3,cutoff=0)
     assert_equal(list(list(p) for p in paths),[])
 
-@raises(nx.NetworkXError)
+@raises(nx.NodeNotFound)
 def test_source_missing():
     G = nx.Graph()
     G.add_path([1,2,3])
     paths = list(nx.all_simple_paths(nx.MultiGraph(G),0,3))
 
-@raises(nx.NetworkXError)
+@raises(nx.NodeNotFound)
 def test_target_missing():
     G = nx.Graph()
     G.add_path([1,2,3])
@@ -139,14 +139,14 @@ def test_weight_name():
     paths = list(nx.shortest_simple_paths(G, 0, 3, weight='foo'))
     solution = [[0, 6, 5, 4, 3], [0, 1, 2, 3]]
     assert_equal(paths, solution)
-    
-@raises(nx.NetworkXError)
+
+@raises(nx.NodeNotFound)
 def test_ssp_source_missing():
     G = nx.Graph()
     G.add_path([1,2,3])
     paths = list(nx.shortest_simple_paths(G, 0, 3))
 
-@raises(nx.NetworkXError)
+@raises(nx.NodeNotFound)
 def test_ssp_target_missing():
     G = nx.Graph()
     G.add_path([1,2,3])
@@ -199,7 +199,7 @@ def test_bidirectional_shortest_path_restricted():
         nx.NetworkXNoPath,
         _bidirectional_shortest_path,
         directed_cycle,
-        0, 3, 
+        0, 3,
         ignore_edges=[(1, 2)],
     )
 
@@ -225,7 +225,7 @@ def test_bidirectional_dijksta_restricted():
     XG3.add_weighted_edges_from([[0, 1, 2], [1, 2, 12],
                                  [2, 3, 1], [3, 4, 5],
                                  [4, 5, 1], [5, 0, 10]])
-    validate_length_path(XG, 's', 'v', 9, 
+    validate_length_path(XG, 's', 'v', 9,
                          *_bidirectional_dijkstra(XG, 's', 'v'))
     validate_length_path(XG, 's', 'v', 10,
                          *_bidirectional_dijkstra(XG, 's', 'v', ignore_nodes=['u']))
@@ -259,4 +259,3 @@ def test_bidirectional_dijkstra_no_path():
     G.add_path([1, 2, 3])
     G.add_path([4, 5, 6])
     path = _bidirectional_dijkstra(G, 1, 6)
-
diff --git a/networkx/exception.py b/networkx/exception.py
index 72696b24..4c1a1ec0 100644
--- a/networkx/exception.py
+++ b/networkx/exception.py
@@ -52,3 +52,9 @@ class NetworkXUnbounded(NetworkXAlgorithmError):
 
 class NetworkXNotImplemented(NetworkXException):
     """Exception raised by algorithms not implemented for a type of graph."""
+
+class NotFound(NetworkXException):
+    """Exception"""
+
+class NodeNotFound(NotFound):
+    """Exception raised if node is not present in the graph"""