import weakref
import gc

class C(object):
    def __init__(self, i):
        self.i = i
        self.loop = self

def callback(ignored):
    ouch[:] = [wr() for wr in WRs]

Cs = [C(i) for i in range(2)]
WRs = [weakref.ref(c, callback) for c in Cs]
c = None

ouch = []

gc.collect()
del Cs[:]
gc.collect()

for x in ouch:
    print "type(x) =", type(x)
    if x is not None:
        print "x.__dict__ =", x.__dict__
        print "x.i =", x.i