Add decorators to utility functions

inettopology/util/decorators.py

@@ -0,0 +1,27 @@
+import functools 
+import collections
+
+
+class factory(object):
+  """ Decorate a function so that it becomes a cached factory."""
+
+  def __init__(self, func):
+    self.func = func
+    self.cache = {}
+
+  def __call__(self, *args):
+    if not isinstance(args, collections.Hashable):
+      return self.func(args)
+    if args in self.cache:
+      return self.cache[args]
+    else:
+      value = self.func(*args)
+      self.cache[args] = value
+      return value
+
+  def __doc__(self):
+    return self.func.__doc__
+
+  def __get__(self, obj, objtype):
+    '''Support instance methods'''
+    return functools.partial(self.__call__, obj)