# Copyright (c) 2011 Edward Langley
# 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 the project's author 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
# HOLDER 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.

class LazyLoad(object):
    def __init__(self, __func_, *args, **kwargs):
        self.__func = __func_
        self.__args = list(args)
        self.__kwargs = kwargs
    def __get__(self, inst, cls):
        tb = cls.__dict__
        nm = [x for x in tb.keys() if id(tb[x]) == id(self)][0]
        setattr(inst, nm, self.__func(*self.__args, **self.__kwargs))
        return getattr(inst, nm)

def func(a,b,c):
    print a,b,c
    return a+b,c

class a(object):
    b = LazyLoad(func, 1,2,3)
    c = LazyLoad(func, 2,3,4)
    d = LazyLoad(func, 3,4,5)
    __e = LazyLoad(func, 4,5,6)
    def __str__(self): return str(self.__e)