ENH: created a cached_property decorator

rocketpy/tools.py

@@ -0,0 +1,21 @@
+_NOT_FOUND = object()
+
+
+class cached_property:
+    def __init__(self, func):
+        self.func = func
+        self.attrname = None
+        self.__doc__ = func.__doc__
+
+    def __set_name__(self, owner, name):
+        self.attrname = name
+
+    def __get__(self, instance, owner=None):
+        if instance is None:
+            return self
+        cache = instance.__dict__
+        val = cache.get(self.attrname, _NOT_FOUND)
+        if val is _NOT_FOUND:
+            val = self.func(instance)
+            cache[self.attrname] = val
+        return val