def lazyprop(fn):
    attr_name = '_lazy_' + fn.__name__
    @property
    def _lazyprop(self):
        if not hasattr(self, attr_name):
            setattr(self, attr_name, fn(self))
        return getattr(self, attr_name)
    return _lazyprop


class Test(object):

    @lazyprop
    def a(self):
        print 'generating "a"'
        return range(5)
    
t = Test()
b = t.a
%timeit b = t.a

class lazy_property(object):
    '''
    meant to be used for lazy evaluation of an object attribute.
    property should represent non-mutable data, as it replaces itself.
    '''

    def __init__(self,fget):
        self.fget = fget
        self.func_name = fget.__name__


    def __get__(self,obj,cls):
        if obj is None:
            return None
        value = self.fget(obj)
        setattr(obj,self.func_name,value)
        return value
class Test(object):

    @lazy_property
    def a(self):
        print 'generating "a"'
        return range(5)
    
t = Test()
b = t.a    
%timeit b = t.a