>>> a = 1
>>> d = {'a':a}
>>> d['a']
1
>>> a = 2
>>> d['a']
1

>>> a = 1
>>> d = {'a':magical pointer to a}
>>> d['a']
1
>>> a = 2
>>> d['a']
2

>>> a = mutable_structure(1)
>>> d = {'a':a}
>>> d['a']
1
>>> a.setValue(2)
>>> d['a']
2

class mutable_structure:
  def __init__(self, val):
    self.val = val

  def __repr__(self):
    return self.val

a = [1]
d = {'a': a}
a[0] = 2
print d['a'][0]

class Mutable(object):
    pass

a = Mutable()
a.value = 1

d = {'a':a}
a.value = 3

class DRefsA(object):
    a = 4

    @property
    def d(self):
        return self.a

    @d.setter
    def d(self, value):
        self.a = value

a = 1
d = {'a': lambda  : a}
print(d['a']()) #output 1
a = 2
print(d['a']()) #output 2