python - 创建无法 pickle 的对象

Question

我如何轻松地创建一个不能被 pickle 的对象来测试我的 rpc 代码中的边缘情况？

它需要是:

1. 简单
2. 可靠(预计不会在未来版本的 python 或 pickle 中崩溃)
3. 跨平台

编辑:预期用途看起来像这样:

class TestRPCServer:
    def foo(self):
        return MagicalUnpicklableObject()

def test():
    with run_rpc_server_and_connect_to_it() as proxy:
        with nose.assert_raises(pickle.PickleError):
            proxy.foo()

Answer 1

如果您只需要一个在 pickle 时会抛出异常的对象，为了测试的目的，您可以炸毁 __getstate__ method .

>>> class C:
...     def __getstate__(self):
...         raise Exception
... 
>>> pickle.dumps(C())
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pickle.py", line 1374, in dumps
    Pickler(file, protocol).dump(obj)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pickle.py", line 224, in dump
    self.save(obj)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pickle.py", line 723, in save_inst
    stuff = getstate()
  File "<stdin>", line 3, in __getstate__
Exception

---

如果您想要一个不那么人为的场景，请考虑使用操作系统资源(如文件句柄、套接字或线程等)的对象。

>>> with open('spam.txt', 'w') as f:
...     pickle.dumps(f)
... 
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pickle.py", line 1374, in dumps
    Pickler(file, protocol).dump(obj)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pickle.py", line 224, in dump
    self.save(obj)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pickle.py", line 306, in save
    rv = reduce(self.proto)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/copy_reg.py", line 70, in _reduce_ex
    raise TypeError, "can't pickle %s objects" % base.__name__
TypeError: can't pickle file objects