73 lines
1.9 KiB
Python
73 lines
1.9 KiB
Python
# -*- encoding:utf-8 -*-
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"""
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lazy工具模块
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"""
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from __future__ import print_function
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from __future__ import absolute_import
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from __future__ import division
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import sys
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import weakref
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class LazyFunc(object):
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"""描述器类：作用在类中需要lazy的对象方法上"""
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def __init__(self, func):
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"""
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外部使用eg：
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class BuyCallMixin(object):
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@LazyFunc
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def buy_type_str(self):
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return "call"
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@LazyFunc
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def expect_direction(self):
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return 1.0
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"""
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self.func = func
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self.cache = weakref.WeakKeyDictionary()
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def __get__(self, instance, owner):
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"""描述器__get__，使用weakref.WeakKeyDictionary将以实例化的instance加入缓存"""
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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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ret = self.func(instance)
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self.cache[instance] = ret
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return ret
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def __set__(self, instance, value):
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"""描述器__set__，raise AttributeError，即禁止外部set值"""
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raise AttributeError("LazyFunc set value!!!")
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def __delete__(self, instance):
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"""描述器___delete__从weakref.WeakKeyDictionary cache中删除instance"""
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del self.cache[instance]
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class LazyClsFunc(LazyFunc):
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"""
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描述器类：
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作用在类中需要lazy的类方法上，实际上只是使用__get__(owner, owner)
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替换原始__get__(self, instance, owner)
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"""
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def __get__(self, instance, owner):
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"""描述器__get__，使用__get__(owner, owner)替换原始__get__(self, instance, owner)"""
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return super(LazyClsFunc, self).__get__(owner, owner)
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def add_doc(func, doc):
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"""Lazy add doc"""
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func.__doc__ = doc
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def import_module(name):
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"""Lazy impor _module"""
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__import__(name)
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return sys.modules[name]
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