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"""Implementation of the object pool""" |
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import types |
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import attr |
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__all__ = ['ObjectsPool'] |
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def _convert_to_method(function): |
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def _function(_self, *args, **kwargs): |
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return function(*args, **kwargs) |
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return _function |
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@attr.s |
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class ObjectsPool: |
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"""Class of objects that are able to return a reference to an object upon request. |
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Whenever an object is requested, it is checked whether it exists in the pool. |
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Then if it exists, a reference is returned, otherwise a new object is |
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constructed (given the provided callable) and its reference is returned. |
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Arguments: |
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constructor (callable): able to construct the object given arguments |
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objects (dict): the data structure representing the object pool |
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""" |
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@staticmethod |
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def __build_hash(*args, **kwargs): |
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r"""Construct a unique string out of the input \*args and \*\*kwargs.""" |
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return hash('-'.join([str(_) for _ in args] + ['{key}={value}'.format(key=k, value=str(v)) for k, v in kwargs])) |
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constructor = attr.ib(init=True) |
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_objects = attr.ib(init=True, default={}) |
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_build_hash = attr.ib(default=attr.Factory(lambda self: types.MethodType( |
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_convert_to_method(ObjectsPool.__build_hash), self), takes_self=True)) |
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def get_object(self, *args, **kwargs): |
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r"""Request an object from the pool. |
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Get or create an object given the input parameters. Existence in the pool is done using the |
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python-build-in hash function. The input \*args and \*\*kwargs serve as |
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input in the hash function to create unique keys with which to "query" the object pool. |
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Returns: |
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object: the reference to the object that corresponds to the input |
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arguments, regardless of whether it was found in the pool or not |
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""" |
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key = self._build_hash(*args, **kwargs) |
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if key not in self._objects: |
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self._objects[key] = self.constructor(*args, **kwargs) |
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return self._objects[key] |
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@classmethod |
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def new_empty(cls, constructor, build_hash=None): |
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if build_hash is None: |
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build_hash = ObjectsPool.__build_hash |
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return ObjectsPool(constructor, {}, build_hash) |
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boromir674 /
so-magic
