ali01 · January 11, 2013 03:44 · Jan 11, 2013
diff --git a/memoizer.py b/memoizer.py
@@ -0,0 +1,46 @@
+import functools
+import hashlib
+import time
+
+
+def memoize(secs=0):
+  '''Returns a decorator to memoize stateless functions.
+  Args: secs - Amount of time (in seconds) to keep values in the cache;
+               The argument may be a floating point number to indicate a
+               more precise timeout.
+  '''
+
+  def decorator(f):
+    cache = {}
+
+    @functools.wraps(f)
+    def wrapped(*args, **kwargs):
+      args_hash = hash(args)
+      kwargs_keys_hash = hash(frozenset(kwargs.keys()))
+      kwargs_vals_hash = hash(frozenset(kwargs.values()))
+
+      m = hashlib.sha1()
+      m.update(str(args_hash))
+      m.update(str(kwargs_keys_hash))
+      m.update(str(kwargs_vals_hash))
+      key = m.hexdigest()
+
+      time_now = time.time() if secs > 0 else 0
+
+      if key not in cache:
+        # store value along with expire_time in cache
+        value = f(*args, **kwargs)
+        cache[key] = (value, time_now + secs)
+
+      elif secs > 0:
+        # refresh cache
+        expire_time = cache[key][1]
+        if time_now > expire_time:
+          value = f(*args, **kwargs)
+          cache[key] = (value, time_now + secs)
+
+      return cache[key][0]
+
+    return wrapped
+
+  return decorator
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