diff --git a/lazy_evaluation.py b/lazy_evaluation.py index 5f364a65d..c21d2c82f 100644 --- a/lazy_evaluation.py +++ b/lazy_evaluation.py @@ -5,20 +5,35 @@ Lazily-evaluated property pattern in Python. https://en.wikipedia.org/wiki/Lazy_evaluation -http://stevenloria.com/lazy-evaluated-properties-in-python/ + +References: +bottle +https://github.com/bottlepy/bottle/blob/cafc15419cbb4a6cb748e6ecdccf92893bb25ce5/bottle.py#L270 +django +https://github.com/django/django/blob/ffd18732f3ee9e6f0374aff9ccf350d85187fac2/django/utils/functional.py#L19 +pip +https://github.com/pypa/pip/blob/cb75cca785629e15efb46c35903827b3eae13481/pip/utils/__init__.py#L821 +pyramimd +https://github.com/Pylons/pyramid/blob/7909e9503cdfc6f6e84d2c7ace1d3c03ca1d8b73/pyramid/decorator.py#L4 +werkzeug +https://github.com/pallets/werkzeug/blob/5a2bf35441006d832ab1ed5a31963cbc366c99ac/werkzeug/utils.py#L35 """ -def lazy_property(fn): - """Decorator that makes a property lazy-evaluated.""" - attr_name = '_lazy_' + fn.__name__ +import functools + + +class lazy_property(object): + def __init__(self, function): + self.function = function + functools.update_wrapper(self, function) - @property - def _lazy_property(self): - if not hasattr(self, attr_name): - setattr(self, attr_name, fn(self)) - return getattr(self, attr_name) - return _lazy_property + def __get__(self, obj, type_): + if obj is None: + return self + val = self.function(obj) + obj.__dict__[self.function.__name__] = val + return val class Person(object):