A simple decorator to define memoized properties in Python

memoized_property.py

import weakref


class memoized_property(property):

    def __init__(self, *args, **kwargs):
        super(memoized_property, self).__init__(*args, **kwargs)
        self.data = weakref.WeakKeyDictionary()

    def __get__(self, instance, owner=None):
        result = self.data.get(instance, None) if instance is not None else None
        if result is None:
            result = super(memoized_property, self).__get__(instance, owner)
            if instance is not None:
                self.data[instance] = result
        return result