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-rw-r--r--changes/feature_4784_memoize-decorator1
-rw-r--r--src/leap/common/decorators.py113
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