adding read-from-config boilerplate

python/libraries/cache-libraries/cached-property.py

@@ -0,0 +1,43 @@
+"""Caching utilities."""
+
+
+class cachedproperty:
+    """A decorator for caching a property's result.
+
+    Similar to `property`, but the wrapped method's result is cached
+    on the instance. This is achieved by setting an entry in the object's
+    instance dictionary with the same name as the property. When the name
+    is later accessed, the value in the instance dictionary takes precedence
+    over the (non-data descriptor) property.
+
+    This is useful for implementing lazy-loaded properties.
+
+    The cache can be invalidated via `delattr()`, or by modifying `__dict__`
+    directly. It will be repopulated on next access.
+
+    .. versionadded:: 6.3.0
+    """
+
+    def __init__(self, func, doc=None):
+        """Initialize the descriptor."""
+        self.func = self.__wrapped__ = func
+
+        if doc is None:
+            doc = func.__doc__
+        self.__doc__ = doc
+
+    def __get__(self, obj, objtype=None):
+        """Implement descriptor getter.
+
+        Calculate the property's value and then store it in the
+        associated object's instance dictionary.
+        """
+        if obj is None:
+            return self
+
+        value = obj.__dict__[self.func.__name__] = self.func(obj)
+        return value
+
+    def __repr__(self):
+        """Return repr(self)."""
+        return "<%s %s>" % (self.__class__.__name__, self.func)