class ChangeTracker(object):
'''
Tracks changes in objects that are registered with it.
To register an object, use `.check_in(obj)`. It will return `True`. Every
time `.check_in` will be called with the same object, it will return
whether the object changed since the last time it was checked in.
'''
def __init__(self):
self.library = WeakKeyIdentityDict()
'''dictoid mapping from objects to their last pickle value.'''
def check_in(self, thing):
'''
Check in an object for change tracking.
The first time you check in an object, it will return `True`. Every
time `.check_in` will be called with the same object, it will return
whether the object changed since the last time it was checked in.
'''
new_pickle = cPickle.dumps(thing, 2)
if thing not in self.library:
self.library[thing] = new_pickle
return True
# thing in self.library
previous_pickle = self.library[thing]
if previous_pickle == new_pickle:
return False
else:
self.library[thing] = new_pickle
return True
def __contains__(self, thing):
'''Return whether `thing` is tracked.'''
return self.library.__contains__(thing)
