diff --git a/LICENSE b/LICENSE index c293801..02c5247 100644 --- a/LICENSE +++ b/LICENSE @@ -75,3 +75,33 @@ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */ + +utils.cached_property extracted from Celery +------------------------------------------- +Copyright (c) 2009-2011, Ask Solem and contributors. +All rights reserved. + +Redistribution and use in source and binary forms, with or without +modification, are permitted provided that the following conditions are met: + + * Redistributions of source code must retain the above copyright notice, + this list of conditions and the following disclaimer. + * Redistributions in binary form must reproduce the above copyright + notice, this list of conditions and the following disclaimer in the + documentation and/or other materials provided with the distribution. + +Neither the name of Ask Solem nor the names of its contributors may be used +to endorse or promote products derived from this software without specific +prior written permission. + +THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" +AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, +THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR +PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS +BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR +CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF +SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS +INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN +CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) +ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE +POSSIBILITY OF SUCH DAMAGE. diff --git a/compressor/utils.py b/compressor/utils.py index fbfa868..0e48853 100644 --- a/compressor/utils.py +++ b/compressor/utils.py @@ -192,3 +192,70 @@ class AppSettings(object): def issetting(self, (name, value)): return name == name.upper() + + +class cached_property(object): + """Property descriptor that caches the return value + of the get function. + + *Examples* + + .. code-block:: python + + @cached_property + def connection(self): + return Connection() + + @connection.setter # Prepares stored value + def connection(self, value): + if value is None: + raise TypeError("Connection must be a connection") + return value + + @connection.deleter + def connection(self, value): + # Additional action to do at del(self.attr) + if value is not None: + print("Connection %r deleted" % (value, )) + """ + + def __init__(self, fget=None, fset=None, fdel=None, doc=None): + self.__get = fget + self.__set = fset + self.__del = fdel + self.__doc__ = doc or fget.__doc__ + self.__name__ = fget.__name__ + self.__module__ = fget.__module__ + + def __get__(self, obj, type=None): + if obj is None: + return self + try: + return obj.__dict__[self.__name__] + except KeyError: + value = obj.__dict__[self.__name__] = self.__get(obj) + return value + + def __set__(self, obj, value): + if obj is None: + return self + if self.__set is not None: + value = self.__set(obj, value) + obj.__dict__[self.__name__] = value + + def __delete__(self, obj): + if obj is None: + return self + try: + value = obj.__dict__.pop(self.__name__) + except KeyError: + pass + else: + if self.__del is not None: + self.__del(obj, value) + + def setter(self, fset): + return self.__class__(self.__get, fset, self.__del) + + def deleter(self, fdel): + return self.__class__(self.__get, self.__set, fdel)