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| -rw-r--r-- | changes/feature_4784_memoize-decorator | 1 | ||||
| -rw-r--r-- | src/leap/common/decorators.py | 113 |
2 files changed, 114 insertions, 0 deletions
diff --git a/changes/feature_4784_memoize-decorator b/changes/feature_4784_memoize-decorator new file mode 100644 index 0000000..5e6bf82 --- /dev/null +++ b/changes/feature_4784_memoize-decorator @@ -0,0 +1 @@ + o Add memoized_method decorator. Closes: #4784 diff --git a/src/leap/common/decorators.py b/src/leap/common/decorators.py new file mode 100644 index 0000000..ec6171a --- /dev/null +++ b/src/leap/common/decorators.py @@ -0,0 +1,113 @@ +# -*- coding: utf-8 -*- +# decorators.py +# Copyright (C) 2013 LEAP +# +# This program is free software: you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation, either version 3 of the License, or +# (at your option) any later version. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see <http://www.gnu.org/licenses/>. +""" +Useful decorators. +""" +import collections +import functools +import logging + +logger = logging.getLogger(__name__) + + +class _memoized(object): + """ + Decorator. + + Caches a function's return value each time it is called. + If called later with the same arguments, the cached value is returned + (not reevaluated). + """ + def __init__(self, func, ignore_kwargs=None, is_method=False): + """ + :param ignore_kwargs: If True, ignore all kwargs. + If tuple, ignore those kwargs. + :type ignore_kwargs: bool, tuple or None + :param is_method: whether the decorated function is a method. + (ignores the self argument if so). + :type is_method: True + """ + self.ignore_kwargs = ignore_kwargs if ignore_kwargs else [] + self.is_method = is_method + self.func = func + + # TODO should put bounds to the cache dict so we do not + # consume a huge amount of memory. + self.cache = {} + + def __call__(self, *args, **kwargs): + """ + Executes the call. + + :tyoe args: tuple + :type kwargs: dict + """ + if self.is_method: + # forget about `self` as key + key_args = args[1:] + if self.ignore_kwargs is True: + key = key_args + else: + key = (key_args, frozenset( + [(k, v) for k, v in kwargs.items() + if k not in self.ignore_kwargs])) + + if not isinstance(key, collections.Hashable): + # uncacheable. a list, for instance. + # better to not cache than blow up. + logger.warning("Key is not hashable, bailing out!") + return self.func(*args, **kwargs) + + if key in self.cache: + logger.debug("Got value from cache...") + return self.cache[key] + else: + try: + value = self.func(*args, **kwargs) + except Exception as exc: + logger.error("Exception while calling function: %r" % (exc,)) + value = None + self.cache[key] = value + return value + + def __repr__(self): + """ + Return the function's docstring. + """ + return self.func.__doc__ + + def __get__(self, obj, objtype): + """ + Support instance methods. + """ + return functools.partial(self.__call__, obj) + + +def memoized_method(function=None, ignore_kwargs=None): + """ + Wrap _memoized to allow for deferred calling + + :type function: callable, or None. + :type ignore_kwargs: None, True or tuple. + """ + if function: + return _memoized(function, is_method=True) + else: + def wrapper(function): + return _memoized( + function, ignore_kwargs=ignore_kwargs, is_method=True) + return wrapper |