this is often misunderstood about python, especially if you are accustomed to other languages, such as C/C++.
>>> class thing(object):
... def __init__(self, some):
... self.some = some
... def add_on(self, addition):
... self.some = self.some + addition
...
>>> a = thing("hello")
>>> print(a.some)
hello
>>> b = a
>>> print(b)
<__main__.thing object at 0x7f9d267cf7f0>
>>> print(a)
<__main__.thing object at 0x7f9d267cf7f0>
>>> print(b.some)
hello
>>> a.add_on(", world")
>>> print(a.some)
hello, world
>>> print(b.some)
hello, world
>>> print(a)
<__main__.thing object at 0x7f9d267cf7f0>
>>> print(b)
<__main__.thing object at 0x7f9d267cf7f0>
