2.4 defines groupby, so there's no need to define our own.

src/utils/iter.py

@@ -27,6 +27,7 @@
 # POSSIBILITY OF SUCH DAMAGE.
 ###
 
+import sys
 import new
 import random
 
@@ -48,21 +49,22 @@ def trueCycle(iterable):
         if not yielded:
             raise StopIteration
 
-def groupby(key, iterable):
-    if key is None:
-        key = lambda x: x
-    it = iter(iterable)
-    value = it.next() # If there are no items, this takes an early exit
-    oldkey = key(value)
-    group = [value]
-    for value in it:
-        newkey = key(value)
-        if newkey != oldkey:
-            yield group
-            group = []
-            oldkey = newkey
-        group.append(value)
-    yield group
+if sys.version_info < (2, 4, 0):
+    def groupby(key, iterable):
+        if key is None:
+            key = lambda x: x
+        it = iter(iterable)
+        value = it.next() # If there are no items, this takes an early exit
+        oldkey = key(value)
+        group = [value]
+        for value in it:
+            newkey = key(value)
+            if newkey != oldkey:
+                yield group
+                group = []
+                oldkey = newkey
+            group.append(value)
+        yield group
 
 def partition(p, iterable):
     """Partitions an iterable based on a predicate p.