# Copyright (C) 2014  Andrey Golovizin
# 
# 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/>.


import functools

def cached_property(fun):
    """A memoize decorator for class properties."""
    @functools.wraps(fun)
    def get(self):
        try:
            return self._cache[fun]
        except AttributeError:
            self._cache = {}
        except KeyError:
            pass
        ret = self._cache[fun] = fun(self)
        return ret
    return property(get)