[Checkins] SVN: Products.ZCatalog/trunk/ Optimized length calculation of Lazy classes.

[Hanno Schlichting]

Log message for revision 119143:
  Optimized length calculation of Lazy classes.
  

Changed:
  U   Products.ZCatalog/trunk/CHANGES.txt
  U   Products.ZCatalog/trunk/src/Products/ZCatalog/Lazy.py

-=-
Modified: Products.ZCatalog/trunk/CHANGES.txt
===================================================================
--- Products.ZCatalog/trunk/CHANGES.txt	2010-12-26 16:53:37 UTC (rev 119142)
+++ Products.ZCatalog/trunk/CHANGES.txt	2010-12-26 18:38:12 UTC (rev 119143)
@@ -4,6 +4,8 @@
 2.13.2 (unreleased)
 -------------------
 
+- Optimized length calculation of Lazy classes.
+  [hannosch]
 
 2.13.1 (2010-12-25)
 -------------------

Modified: Products.ZCatalog/trunk/src/Products/ZCatalog/Lazy.py
===================================================================
--- Products.ZCatalog/trunk/src/Products/ZCatalog/Lazy.py	2010-12-26 16:53:37 UTC (rev 119142)
+++ Products.ZCatalog/trunk/src/Products/ZCatalog/Lazy.py	2010-12-26 18:38:12 UTC (rev 119143)
@@ -13,22 +13,22 @@
 
 from itertools import islice, count
 
+_marker = object()
 
+
 class Lazy(object):
 
     # Allow (reluctantly) access to unprotected attributes
     __allow_access_to_unprotected_subobjects__=1
+    _len = _marker
 
     def __repr__(self):
         return repr(list(self))
 
     def __len__(self):
         # This is a worst-case len, subclasses should try to do better
-        try:
+        if self._len is not _marker:
             return self._len
-        except AttributeError:
-            pass
-
         l = len(self._data)
         while 1:
             try:
@@ -127,17 +127,16 @@
     def __len__(self):
         # Make len of LazyCat only as expensive as the lens
         # of its underlying sequences
+        if self._len is not _marker:
+            return self._len
+        l = 0
         try:
-            return self._len
-        except Exception:
-            try:
-                l = 0
-                for s in self._seq:
-                    l += len(s)
-            except AttributeError:
-                l = len(self._data)
-            self._len = l
-            return l
+            for s in self._seq:
+                l += len(s)
+        except AttributeError:
+            l = len(self._data)
+        self._len = l
+        return l
 
 
 class LazyMap(Lazy):
@@ -267,7 +266,10 @@
         self._seq = seq
 
     def __len__(self):
-        return len(self._seq)
+        if self._len is not _marker:
+            return self._len
+        self._len = len(self._seq)
+        return self._len
 
     def __getitem__(self, index):
         return self._seq[index][1]