Get object by id()?

You'll probably want to consider implementing it another way. Are you aware of the weakref module?

(Edited) The Python weakref module lets you keep references, dictionary references, and proxies to objects without having those references count in the reference counter. They're like symbolic links.

If the object is still there, this can be done by ctypes:

import ctypes
a = "hello world"
print ctypes.cast(id(a), ctypes.py_object).value

output:

hello world

If you don't know whether the object is still there, this is a recipe for undefined behavior and weird crashes or worse, so be careful.