From 501a1a37c0db7a48e82e6e18c319ab2dd2e779e8 Mon Sep 17 00:00:00 2001
From: Jay Hutchinson <jlhutch@gmail.com>
Date: Sun, 10 Oct 2010 13:19:19 -0500
Subject: Removed unnecessary __del__ from lrucache. Added a few comments.

---
 pylru.py | 26 ++++++--------------------
 test.py  |  4 ++++
 2 files changed, 10 insertions(+), 20 deletions(-)

diff --git a/pylru.py b/pylru.py
index 83e78ff..50dd597 100644
--- a/pylru.py
+++ b/pylru.py
@@ -51,10 +51,9 @@ class lrucache(object):
         self.table = {}
 
     
-        # Initalize the list with 'size' empty nodes. Create the first node and
+        # Initalize the list with one empty node. Create a node and
         # assign it to the 'head' variable, which represents the head node in the
-        # list. Then each iteration of the loop creates a subsequent node and
-        # inserts it directly after the head node.
+        # list.
         self.head = _dlnode()
         self.head.next = self.head
         self.head.prev = self.head
@@ -189,7 +188,8 @@ class lrucache(object):
                 
         return self.listSize
             
-	
+	# Increases the size of the cache by inserting n empty nodes at the tail of
+    # the list.
     def addTailNode(self, n):
         for i in range(n):
             node = _dlnode()
@@ -201,7 +201,8 @@ class lrucache(object):
         
         self.listSize += n
 
-
+    # Decreases the size of the list by removing n nodes from the tail of the
+    # list.
     def removeTailNode(self, n):
         assert self.listSize > 1   # Invarient. XXX REMOVE this line XXX
         for i in range(n):
@@ -224,21 +225,6 @@ class lrucache(object):
             
         self.listSize -= n
   
-    def __del__(self):
-        # When we are finished with the cache, special care is taken to break the
-        # doubly linked list, so that there are no cycles. First all of the 'prev'
-        # links are broken. Then the 'next' link between the 'tail' node and the
-        # 'head' node is broken.
-    
-        tail = self.head.prev
-    
-        node = self.head
-        while node.prev is not None:
-            node = node.prev
-            node.next.prev = None
-      
-        tail.next = None
-  
   
     # This method adjusts the doubly linked list so that 'node' directly preeceds
     # the 'head' node. Note that it works even if 'node' already directly
diff --git a/test.py b/test.py
index fd849d0..8ed5fee 100644
--- a/test.py
+++ b/test.py
@@ -2,6 +2,9 @@
 from pylru import *
 import random
 
+# This tests PyLRU by fuzzing it with random operations, then checking the
+# results against another, simpler, LRU cache implementation.
+
 class simplelrucache:
   
     def __init__(self, size):
@@ -161,6 +164,7 @@ def testDecorator():
 if __name__ == '__main__':
     
     random.seed()
+
     
     for i in range(20):
         testcache()
-- 
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