5 ms·

Hey Amelius, thanks for the message. Gonna be honest, I'm not sure what you mean by cycles. Can you elaborate a bit?

emidln 9y ago
a = {} b = {} a["b"] = b b["a"] = a a == deserialize(serialize(a))
amelius 9y ago
Roughly speaking, by cycles I mean a structure that refers to itself somehow. For example: A = {} B = {} A["ref"] = B B["ref"] = A So would it be possible to serialize A and B, and of course to deserialize them? Note that print A gives {'ref': {'ref': {...}}} which is of course not a suitable serialization, since you can't recover the original structure from it.
- jackqu7 9y ago
  Yes, this is possible as long as the second level nested object has a role to stop infinite recursion from occurring. Cycles are not automatically detected. class BaseMapper(Mapper): __type__ = TestType score = Integer() nest = Nested('NestedMapper') __roles__ = {'nested': blacklist('nest')} class NestedMapper(Mapper): __type__ = TestType back = Nested('BaseMapper', role='nested') name = String() obj2 = TestType(name='test') obj = TestType(score=5, nest=obj2) obj2.back = obj >> BaseMapper(obj=obj).serialize() {'nest': {'back': {'score': 5}, 'name': 'test'}, 'score': 5}
  - amelius 9y ago
    The output isn't clear to me: {'nest': {'back': {'score': 5}, 'name': 'test'}, 'score': 5} How can this be mapped back unambiguously to a cyclic structure? (I might be wrong but it seems to me that the act of serialization has simply expanded the cycle one level deep.)
  - arnarbi 9y ago
    That's not a solution as it will not restore the same object graph, it will just repeat values. One way is to to store a table of objects (as identified by id()) encountered during serialization, indexed by the order you encounter them. If you encounter an object you have already serialized, serialize an index into that table. On deserialization, construct the same kind of table, and deserialize an index with a reference to the same object. See e.g. AMF for an example format that does this: https://en.wikipedia.org/wiki/Action_Message_Format https://en.wikipedia.org/wiki/Action_Message_Format

a = {} b = {} a["b"] = b b["a"] = a a == deserialize(serialize(a))

Roughly speaking, by cycles I mean a structure that refers to itself somehow. For example: A = {} B = {} A["ref"] = B B["ref"] = A So would it be possible to serialize A and B, and of course to deserialize them? Note that print A gives {'ref': {'ref': {...}}} which is of course not a suitable serialization, since you can't recover the original structure from it.

jackqu7 9y ago
Yes, this is possible as long as the second level nested object has a role to stop infinite recursion from occurring. Cycles are not automatically detected. class BaseMapper(Mapper): __type__ = TestType score = Integer() nest = Nested('NestedMapper') __roles__ = {'nested': blacklist('nest')} class NestedMapper(Mapper): __type__ = TestType back = Nested('BaseMapper', role='nested') name = String() obj2 = TestType(name='test') obj = TestType(score=5, nest=obj2) obj2.back = obj >> BaseMapper(obj=obj).serialize() {'nest': {'back': {'score': 5}, 'name': 'test'}, 'score': 5}
- amelius 9y ago
  The output isn't clear to me: {'nest': {'back': {'score': 5}, 'name': 'test'}, 'score': 5} How can this be mapped back unambiguously to a cyclic structure? (I might be wrong but it seems to me that the act of serialization has simply expanded the cycle one level deep.)
- arnarbi 9y ago
  That's not a solution as it will not restore the same object graph, it will just repeat values. One way is to to store a table of objects (as identified by id()) encountered during serialization, indexed by the order you encounter them. If you encounter an object you have already serialized, serialize an index into that table. On deserialization, construct the same kind of table, and deserialize an index with a reference to the same object. See e.g. AMF for an example format that does this: https://en.wikipedia.org/wiki/Action_Message_Format https://en.wikipedia.org/wiki/Action_Message_Format