类型错误：不能腌制结构对象

如何解决类型错误：不能腌制结构对象

我是 python 包 Construct 的维护者，我寻求帮助使这个库可以pickle。有人来找我，要求它可以泡在云朵上。不幸的是，我所拥有的课程既不能腌制，也不能用 cloudpickle 或 dill-able。请帮忙。

相关票证是：https://github.com/construct/construct/issues/894

$ python3
Python 3.6.9 (default,Oct  8 2020,12:12:24) 
[GCC 8.4.0] on linux
Type "help","copyright","credits" or "license" for more information.
>>> import cloudpickle
>>> import construct
>>> cloudpickle.dumps(construct.Byte)
Traceback (most recent call last):
  File "<stdin>",line 1,in <module>
  File "/usr/local/lib/python3.6/dist-packages/cloudpickle/cloudpickle_fast.py",line 102,in dumps
    cp.dump(obj)
  File "/usr/local/lib/python3.6/dist-packages/cloudpickle/cloudpickle_fast.py",line 563,in dump
    return Pickler.dump(self,obj)
  File "/usr/lib/python3.6/pickle.py",line 409,in dump
    self.save(obj)
  File "/usr/lib/python3.6/pickle.py",line 521,in save
    self.save_reduce(obj=obj,*rv)
  File "/usr/lib/python3.6/pickle.py",line 634,in save_reduce
    save(state)
  File "/usr/lib/python3.6/pickle.py",line 476,in save
    f(self,obj) # Call unbound method with explicit self
  File "/usr/lib/python3.6/pickle.py",line 821,in save_dict
    self._batch_setitems(obj.items())
  File "/usr/lib/python3.6/pickle.py",line 847,in _batch_setitems
    save(v)
  File "/usr/lib/python3.6/pickle.py",line 496,in save
    rv = reduce(self.proto)
TypeError: can't pickle Struct objects

莳萝也有同样的错误。 Pickle 模块产生一行错误。

解决方法

已解决：该错误给了我一条线索。我试图腌制的字节类对象是一个 FormatField，与 Struct 类无关。经过几个小时的思考，我才意识到 Struct 指的是 struct.Struct 而不是 constructor.Struct。去掉之后就可以正常序列化了。

空的construct.Struct 类对象序列化没有问题。

违规代码：

class FormatField(Construct):
    def __init__(self,endianity,format):
        if endianity not in list("=<>"):
            raise FormatFieldError("endianity must be like: = < >",endianity)
        if format not in list("fdBHLQbhlqe?"):
            raise FormatFieldError("format must be like: f d B H L Q b h l q e ?",format)

        super().__init__()
        self.fmtstr = endianity+format
        self.length = struct.calcsize(endianity+format)
        self.packer = struct.Struct(endianity+format) # <---- culprit