[geneagrapher] 163/226: - Replaced loop with list comprehension. - Modified Graph.get_node to raise exception when the node requested does not exist.

[Doug Torrance]

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dtorrance-guest pushed a commit to branch master
in repository geneagrapher.

commit 76e00bbedabf88ed0a5f849dbef336f569d05c55
Author: David Alber <alber.david at gmail.com>
Date:   Wed Nov 2 22:02:19 2011 -0700

    - Replaced loop with list comprehension.
    - Modified Graph.get_node to raise exception when the node requested does
      not exist.
---
 geneagrapher/graph/graph.py | 11 ++++-------
 tests/test_graph_methods.py |  3 +--
 2 files changed, 5 insertions(+), 9 deletions(-)

diff --git a/geneagrapher/graph/graph.py b/geneagrapher/graph/graph.py
index 7c08a7b..1e39460 100644
--- a/geneagrapher/graph/graph.py
+++ b/geneagrapher/graph/graph.py
@@ -30,10 +30,10 @@ class Graph:
                 if not isinstance(head, Node):
                     raise TypeError("Unexpected parameter type: expected list of Node objects for 'heads'")
 
-        self.nodes = {}
         if self.heads is not None:
-            for head in self.heads:
-                self.nodes[head.get_id()] = head
+            self.nodes = dict([(head.get_id(), head) for head in self.heads])
+        else:
+            self.nodes = {}
 
     def has_node(self, id):
         """
@@ -46,10 +46,7 @@ class Graph:
         Return the node in the graph with given id. Returns
         None if no such node exists.
         """
-        if self.has_node(id):
-            return self.nodes[id]
-        else:
-            return None
+        return self.nodes[id]
 
     def get_node_list(self): # NOTE: this method is unused
         """
diff --git a/tests/test_graph_methods.py b/tests/test_graph_methods.py
index f137881..907cf91 100644
--- a/tests/test_graph_methods.py
+++ b/tests/test_graph_methods.py
@@ -40,8 +40,7 @@ class TestGraphMethods(unittest.TestCase):
         
     def test007_get_node_not_found(self):
         # Test the get_node() method for a case where the node does not exist.
-        node = self.graph1.get_node(1)
-        self.assertEquals(node, None)
+        self.assertRaises(KeyError, self.graph1.get_node, 1)
         
     def test008_get_node_list(self):
         # Test the get_node_list() method.

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