added negative index and slice support

aaf/iterator.pyx

@@ -11,12 +11,32 @@ cdef class BaseIterator(object):
     def __cinit__(self):
         self._clone_iter = None
 
-    def __getitem__(self, int index):
+    def __getitem__(self, index):
+
+        if isinstance(index, slice):
+            return self._getslice(index)
+
+        index = int(index)
+
+        if index < 0:
+            index = len(self) + index
+
+        if index < 0:
+            raise IndexError("index out of range")
+
         for i, item in enumerate(self):
             if i == index:
                 return item
         raise IndexError("index out of range")
 
+    def _getslice(self, slice_object):
+
+        l = []
+
+        for i in xrange(*slice_object.indices(len(self))):
+            l.append(self[i])
+        return l
+
     def __iter__(self):
         if self._clone_iter:
             return self._clone_iter()

tests/test_iterator.py

@@ -40,8 +40,6 @@ class TestFile(unittest.TestCase):
 
     def test_len(self):
         f = aaf.open(main_test_file)
-
-
         iterable = f.storage.mobs()
 
         assert len(iterable) == 199
@@ -55,10 +53,50 @@ def test_len(self):
         assert count == len(iterable)
         assert len(iterable) == 199
 
-    def test_skip(self):
+    def test_negative_index(self):
+        f = aaf.open(main_test_file)
+        iterable = f.storage.mobs()
+
+
+        last_item = iterable[len(iterable)-1]
+        assert last_item == iterable[-1]
+
+        try:
+            iterable[-10000]
+        except IndexError:
+            pass
+        else:
+            raise
+
+        for i in xrange(len(iterable)):
+            assert iterable[i] == iterable[i-len(iterable)]
+
+    def test_slice(self):
         f = aaf.open(main_test_file)
+        iterable = f.storage.mobs()
+
+
+        s = iterable[1:10]
+        l = []
+        for i in xrange(1, 10):
+            l.append(iterable[i])
+
+        assert s == l
+
+        s = iterable[100:-10:2]
 
+        l = []
 
+        for i in xrange(100, len(iterable)-10, 2):
+            l.append(iterable[i])
+
+        assert s == l
+
+        l = iterable[-1000: 1000]
+
+
+    def test_skip(self):
+        f = aaf.open(main_test_file)
         iterable = f.storage.mobs()
 
         assert len(iterable) == 199