mirror of
https://github.com/wassname/catalyst.git
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Eddie Hebert
16fd6681a6
More documentation to follow in release notes. Based on lazy-mainline branch, see for more details. Also-By: Jean Bredeche <jean@quantopian.com> Also-By: Andrew Liang <aliang@quantopian.com> Also-By: Abhijeet Kalyan <akalyan@quantopian.com>
88 lines
2.1 KiB
Python
88 lines
2.1 KiB
Python
"""
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Tools for memoization of function results.
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"""
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from zipline.utils.compat import lru_cache
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from weakref import WeakKeyDictionary
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class lazyval(object):
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"""Decorator that marks that an attribute of an instance should not be
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computed until needed, and that the value should be memoized.
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Example
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-------
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>>> from zipline.utils.memoize import lazyval
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>>> class C(object):
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... def __init__(self):
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... self.count = 0
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... @lazyval
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... def val(self):
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... self.count += 1
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... return "val"
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...
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>>> c = C()
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>>> c.count
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0
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>>> c.val, c.count
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('val', 1)
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>>> c.val, c.count
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('val', 1)
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>>> c.val = 'not_val'
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Traceback (most recent call last):
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...
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AttributeError: Can't set read-only attribute.
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>>> c.val
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'val'
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"""
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def __init__(self, get):
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self._get = get
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self._cache = WeakKeyDictionary()
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def __get__(self, instance, owner):
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if instance is None:
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return self
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try:
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return self._cache[instance]
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except KeyError:
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self._cache[instance] = val = self._get(instance)
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return val
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def __set__(self, instance, value):
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raise AttributeError("Can't set read-only attribute.")
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def __delitem__(self, instance):
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del self._cache[instance]
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class classlazyval(lazyval):
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""" Decorator that marks that an attribute of a class should not be
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computed until needed, and that the value should be memoized.
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Example
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-------
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>>> from zipline.utils.memoize import classlazyval
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>>> class C(object):
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... count = 0
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... @classlazyval
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... def val(cls):
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... cls.count += 1
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... return "val"
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...
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>>> C.count
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0
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>>> C.val, C.count
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('val', 1)
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>>> C.val, C.count
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('val', 1)
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"""
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# We don't reassign the name on the class to implement the caching because
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# then we would need to use a metaclass to track the name of the
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# descriptor.
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def __get__(self, instance, owner):
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return super(classlazyval, self).__get__(owner, owner)
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remember_last = lru_cache(1)
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