[Assorted-commits] SF.net SVN: assorted: [687] python-commons/trunk/src/commons/decs.py

[<yan...@us...>]

Revision: 687
          http://assorted.svn.sourceforge.net/assorted/?rev=687&view=rev
Author:   yangzhang
Date:     2008-04-28 17:32:42 -0700 (Mon, 28 Apr 2008)

Log Message:
-----------
added file_memoized, file_string_memoized, pickle_memoized

Modified Paths:
--------------
    python-commons/trunk/src/commons/decs.py

Modified: python-commons/trunk/src/commons/decs.py
===================================================================
--- python-commons/trunk/src/commons/decs.py	2008-04-29 00:31:41 UTC (rev 686)
+++ python-commons/trunk/src/commons/decs.py	2008-04-29 00:32:42 UTC (rev 687)
@@ -7,7 +7,9 @@
 @todo: Move the actual decorators to modules based on their topic.
 """
 
+from __future__ import with_statement
 import functools, inspect, xmlrpclib
+from cPickle import *
 
 def wrap_callable(any_callable, before, after):
     """
@@ -90,3 +92,65 @@
         else:
             return 0
     return wrapper
+
+##########################################################
+
+def file_memoized(serializer, deserializer, pathfunc):
+    """
+    The string result of the given function is saved to the given path.
+
+    Example::
+
+        @file_memoized(lambda x,f: f.write(x),
+                       lambda f: f.read(),
+                       lambda: "/tmp/cache")
+        def foo(): return "hello"
+
+        @file_memoized(pickle.dump,
+                       pickle.load,
+                       lambda x,y: "/tmp/cache-%d-%d" % (x,y))
+        def foo(x,y): return "hello %d %d" % (x,y)
+
+    @param serializer: The function to serialize the return value into a
+                       string.  This should take the return value object and
+                       the file object.
+    @type serializer: function
+
+    @param deserializer: The function te deserialize the cache file contents
+                         into the return value.  This should take the file
+                         object and return a string.
+    type: deserializer: function
+
+    @param pathfunc: Returns the path where the files should be saved.  This
+                     should be able to take the same arguments as the original
+                     function.
+    @type pathfunc: str
+    """
+    def dec(func):
+        @functools.wraps(func)
+        def wrapper(*args, **kwargs):
+            p = pathfunc(*args, **kwargs)
+            try:
+                with file(p) as f:
+                    return deserializer(f)
+            except IOError, (errno, errstr):
+                if errno != 2: raise
+                with file(p, 'w') as f:
+                    x = func(*args, **kwargs)
+                    serializer(x, f)
+                    return x
+        return wrapper
+    return dec
+
+def file_string_memoized(pathfunc):
+    """
+    Wrapper around L{file_memoized} that expects the decorated function to
+    return strings, so the string is written verbatim.
+    """
+    return file_memoized(lambda x,f: f.write(x), lambda f: f.read(), pathfunc)
+
+def pickle_memoized(pathfunc):
+    """
+    Wrapper around L{file_memoized} that uses pickle.
+    """
+    return file_memoized(dump, load, pathfunc)


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