Pickle linked objects

Question

I want to pickle an object and a second object that references the first. When I naively pickle/unpickle the two objects, the reference becomes a copy. How do I preserve t

Answer 1

If you pickle them together, the pickle module keeps track of references and only pickles the foo variable once. Can you pickle both foo and bar together, like this?

import pickle

class Foo(object):
    pass

foo = Foo()
bar = Foo()
bar.foo_ref = foo

with open('tmp.pkl', 'wb') as f:
    pickle.dump((foo, bar), f)
with open('tmp.pkl', 'rb') as f:
    foo2, bar2 = pickle.load(f)

print id(foo) == id(bar.foo_ref) # True
print id(foo2) == id(bar2.foo_ref) # True