- New builtin function enumerate(x), from PEP 279. Example:

enumerate("abc") is an iterator returning (0,"a"), (1,"b"), (2,"c").
  The argument can be an arbitrary iterable object.

Lib/test/test_enumerate.py

@@ -0,0 +1,118 @@
+from __future__ import generators
+import unittest
+
+import test_support
+
+seq, res = 'abc', [(0,'a'), (1,'b'), (2,'c')]
+
+class G:
+    'Sequence using __getitem__'
+    def __init__(self, seqn):
+        self.seqn = seqn
+    def __getitem__(self, i):
+        return self.seqn[i]
+
+class I:
+    'Sequence using iterator protocol'
+    def __init__(self, seqn):
+        self.seqn = seqn
+        self.i = 0
+    def __iter__(self):
+        return self
+    def next(self):
+        if self.i >= len(self.seqn): raise StopIteration
+        v = self.seqn[self.i]
+        self.i += 1
+        return v
+
+class Ig:
+    'Sequence using iterator protocol defined with a generator'
+    def __init__(self, seqn):
+        self.seqn = seqn
+        self.i = 0
+    def __iter__(self):
+        for val in self.seqn:
+            yield val
+
+class X:
+    'Missing __getitem__ and __iter__'
+    def __init__(self, seqn):
+        self.seqn = seqn
+        self.i = 0
+    def next(self):
+        if self.i >= len(self.seqn): raise StopIteration
+        v = self.seqn[self.i]
+        self.i += 1
+        return v
+
+class E:
+    'Test propagation of exceptions'
+    def __init__(self, seqn):
+        self.seqn = seqn
+        self.i = 0
+    def __iter__(self):
+        return self
+    def next(self):
+        3/0
+
+class N:
+    'Iterator missing next()'
+    def __init__(self, seqn):
+        self.seqn = seqn
+        self.i = 0
+    def __iter__(self):
+        return self
+
+class EnumerateTestCase(unittest.TestCase):
+
+    enum = enumerate
+
+    def test_basicfunction(self):
+        self.assertEqual(type(self.enum(seq)), self.enum)
+        e = self.enum(seq)
+        self.assertEqual(iter(e), e)
+        self.assertEqual(list(self.enum(seq)), res)
+        self.enum.__doc__
+
+    def test_getitemseqn(self):
+        self.assertEqual(list(self.enum(G(seq))), res)
+        e = self.enum(G(''))
+        self.assertRaises(StopIteration, e.next)
+
+    def test_iteratorseqn(self):
+        self.assertEqual(list(self.enum(I(seq))), res)
+        e = self.enum(I(''))
+        self.assertRaises(StopIteration, e.next)
+
+    def test_iteratorgenerator(self):
+        self.assertEqual(list(self.enum(Ig(seq))), res)
+        e = self.enum(Ig(''))
+        self.assertRaises(StopIteration, e.next)
+
+    def test_noniterable(self):
+        self.assertRaises(TypeError, self.enum, X(seq))
+
+    def test_illformediterable(self):
+        self.assertRaises(TypeError, list, self.enum(N(seq)))
+
+    def test_exception_propagation(self):
+        self.assertRaises(ZeroDivisionError, list, self.enum(E(seq)))
+
+class MyEnum(enumerate):
+    pass
+
+class SubclassTestCase(EnumerateTestCase):
+
+    enum = MyEnum
+
+def suite():
+    suite = unittest.TestSuite()
+    suite.addTest(unittest.makeSuite(EnumerateTestCase))
+    suite.addTest(unittest.makeSuite(SubclassTestCase))
+    return suite
+
+def test_main():
+    test_support.run_suite(suite())
+
+if __name__ == "__main__":
+    test_main()