用python 3解开python 2对象 [英] Unpickling a python 2 object with python 3

问题描述

我想知道是否可以使用Python 3.4加载在Python 2.4中腌制的对象.

I'm wondering if there is a way to load an object that was pickled in Python 2.4, with Python 3.4.

我一直在大量公司遗留代码上运行2to3，以使其保持最新状态.

I've been running 2to3 on a large amount of company legacy code to get it up to date.

完成此操作后，在运行文件时出现以下错误:

Having done this, when running the file I get the following error:

  File "H:\fixers - 3.4\addressfixer - 3.4\trunk\lib\address\address_generic.py"
, line 382, in read_ref_files
    d = pickle.load(open(mshelffile, 'rb'))
UnicodeDecodeError: 'ascii' codec can't decode byte 0xe2 in position 1: ordinal
not in range(128)

在争用中查看腌制的对象，它是dict中的dict，其中包含键和类型为str的值.

Looking at the pickled object in contention, it's a dict in a dict, containing keys and values of type str.

所以我的问题是:有没有办法用python 3.4加载最初在python 2.4中腌制的对象?

So my question is: Is there a way to load an object, originally pickled in python 2.4, with python 3.4?

推荐答案

您必须告诉pickle.load()如何将Python字节串数据转换为Python 3字符串，或者您可以告诉pickle将其保留为字节.

You'll have to tell pickle.load() how to convert Python bytestring data to Python 3 strings, or you can tell pickle to leave them as bytes.

默认值是尝试将所有字符串数据解码为ASCII，并且解码失败.请参见 pickle.load()文档:

The default is to try and decode all string data as ASCII, and that decoding fails. See the pickle.load() documentation:

可选的关键字参数是 fix_imports ， encoding 和 errors ，它们用于控制对Python 2生成的pickle流的兼容性支持. fix_imports 是正确的，pickle会尝试将旧的Python 2名称映射到Python 3中使用的新名称. encoding 和 errors 告诉pickle如何解码Python 2腌制的8位字符串实例；它们分别默认为"ASCII"和"strict". encoding 可以是字节"，以将这些8位字符串实例读取为字节对象.

Optional keyword arguments are fix_imports, encoding and errors, which are used to control compatibility support for pickle stream generated by Python 2. If fix_imports is true, pickle will try to map the old Python 2 names to the new names used in Python 3. The encoding and errors tell pickle how to decode 8-bit string instances pickled by Python 2; these default to ‘ASCII’ and ‘strict’, respectively. The encoding can be ‘bytes’ to read these 8-bit string instances as bytes objects.

将编码设置为latin1允许您直接导入数据:

Setting the encoding to latin1 allows you to import the data directly:

with open(mshelffile, 'rb') as f:
    d = pickle.load(f, encoding='latin1') 

，但是您需要确认没有使用错误的编解码器对所有字符串进行解码； Latin-1可用于任何输入，因为它将字节值0-255直接映射到前256个Unicode代码点.

but you'll need to verify that none of your strings are decoded using the wrong codec; Latin-1 works for any input as it maps the byte values 0-255 to the first 256 Unicode codepoints directly.

另一种选择是使用encoding='bytes'加载数据，然后解码所有bytes键和值.

The alternative would be to load the data with encoding='bytes', and decode all bytes keys and values afterwards.

请注意，直到3.6.8、3.7.2和3.8.0之前的Python版本，解开Python 2 datetime对象数据已损坏，除非您使用encoding='bytes'.

Note that up to Python versions before 3.6.8, 3.7.2 and 3.8.0, unpickling of Python 2 datetime object data is broken unless you use encoding='bytes'.

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