serializable object references

[Martin Drautzburg]

Is it possible to convert an object into a string that identifies the
object in a way, so it can later be looked up by this string. 
Technically this should be possible, because things like

<__main__.Foo instance at 0xb7cfb6ac>

say everything about an object. But how can I look up the real object,
when I only have this string?

I know such a thing can be achieved with a dictionary that holds
reference-object pairs. Is there another way?