Added utils.iter.one, to grab one value from an iterable.

src/utils/iter.py

@@ -148,6 +148,11 @@ def ilen(iterable):
         i += 1
     return i
 
+def one(iterable):
+    for x in iterable:
+        return x
+    raise ValueError, 'Empty iterable: %r' % iterable
+
 def startswith(long, short):
     longI = iter(long)
     shortI = iter(short)

test/test_utils.py

@@ -384,6 +384,14 @@ class StrTest(SupyTestCase):
 
 
 class IterTest(SupyTestCase):
+    def testOne(self):
+        L = range(3)
+        i = iter(L)
+        self.assertEqual(utils.iter.one(i), 0)
+        self.assertEqual(utils.iter.one(i), 1)
+        self.assertEqual(utils.iter.one(i), 2)
+        self.assertRaises(ValueError, utils.iter.one, i)
+
     def testLimited(self):
         L = range(10)
         self.assertEqual([], list(utils.iter.limited(L, 0)))