鉴于 python 中的泡菜转储，我如何确定使用的协议? [英] Given a pickle dump in python how to I determine the used protocol?

问题描述

假设我有一个泡菜转储——无论是作为一个文件还是一个字符串——我如何确定用于自动创建泡菜转储的协议?

Assume that I have a pickle dump - either as a file or just as a string - how can I determine the protocol that was used to create the pickle dump automatically?

如果是这样，我是否需要阅读整个转储来找出协议，还是可以在 O(1) 中实现?通过 O(1)，我考虑了 pickle 字符串或文件开头的一些标头信息，其读出不需要处理整个转储.

And if so, do I need to read the entire dump to figure out the protocol or can this be achieved in O(1)? By O(1) I think about some header information at the beginning of the pickle string or file whose read out does not require processing the whole dump.

非常感谢！

我对此有更新，显然下面给出的答案在python 3.4下并不总是有效.如果我只是用协议 1 腌制值 True，有时我只能恢复协议 0 :-/

I have an update on this, apparently the answer given below does not always work under python 3.4. If I simply pickle the value True with protocol 1, sometimes I can only recover protocol 0 :-/

推荐答案

您可以使用 picketools 推出自己的方案:

You could roll your own using picketools:

with open('your_pickle_file', 'rb') as fin:
    op, fst, snd = next(pickletools.genops(fin))
    proto = op.proto

PROTO 标记似乎只写为协议为 2 或更大的第一个元素.否则，第一个元素是一个标记或元素，指示协议是 0 还是 1.

It appears that a PROTO marker is only written as the first element where the protocol is 2 or greater. Otherwise, the first element is a marker or element that indicates if the protocol is 0 or 1.

更新以征集更多土地:

pops = pickletools.genops(pickle_source)
proto = 2 if next(pops)[0].proto == 2 else int(any(op.proto for op, fst, snd in pops))

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