Better error-checking.

src/utils.py

@@ -101,6 +101,9 @@ def eachSubstring(s):
 
 def abbrev(strings, d=None):
     """Returns a dictionary mapping unambiguous abbreviations to full forms."""
+    if len(strings) != len(set(strings)):
+        raise ValueError, \
+              'strings given to utils.abbrev have duplicates: %r' % strings
     if d is None:
         d = {}
     for s in strings:

test/test_utils.py

@@ -132,6 +132,10 @@ class UtilsTest(SupyTestCase):
         self.assertEqual(d['fool'], 'fool')
         self.assertEqual(d['foo'], 'foo')
 
+    def testAbbrevFailsWithDups(self):
+        L = ['english', 'english']
+        self.assertRaises(ValueError, utils.abbrev, L)
+
     def testSoundex(self):
         L = [('Euler', 'E460'),
              ('Ellery', 'E460'),