I'd like to create a hashlib instance, update() it, then persist its state in some way. Later, I'd like to recreate the object using this state data, and continue to update() it. Finally, I'd like to get the hexdigest() o the total cumulative run of data. State persistence has to survive across multiple runs.

Example:

import hashlib
m = hashlib.sha1()
m.update('one')
m.update('two')
# somehow, persist the state of m here

#later, possibly in another process
# recreate m from the persisted state
m.update('three')
m.update('four')
print m.hexdigest()
# at this point, m.hexdigest() should be equal to hashlib.sha1().update('onetwothreefour').hextdigets()