为什么可以在unittest.mock.mock.configure_mock中设置dunder/魔术方法？

Question

我在python写了一些单位测试，需要嘲笑一个非常通用的 collections.abc.sized ，所以我开始使用__ len __方法创建一个模拟，其返回值是我想要的任何int。

from unittest.mock import Mock

sized = Mock(**{"__len__.return_value": 8})

attributeErrorgave失败：__len __在帖子结束时产生了追溯，而以下工作：

from unittest.mock import Mock

sized = Mock()
sized.__len__.return_value = 8

# or
from unittest.mock import MagicMock

sized = MagicMock(**{"__len__.return_value": 8})

读取回溯我们看到的是：

1. callablemixin的__ init __ INT __ INT __被调用。
2. Kwargs传递给了Mock的__ INT __方法将传递给 mock.configure_mock（）
3. 名称是getaTtr（）
4. kwargs 方法如果属性名称是魔术，则可以提出属性，也就是说，如果'__％s__'％name [2：-2] ==名称。

这似乎是一个非常任意的限制，我想知道模拟是否有理由不接受 mock.configure_mock（） 。

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
Input In [2], in <cell line: 1>()
----> 1 Mock(**{"__len__.return_value": 0})

File ~/.pyenv/versions/3.10.3/lib/python3.10/unittest/mock.py:1086, in CallableMixin.__init__(self, spec, side_effect, return_value, wraps, name, spec_set, parent, _spec_state, _new_name, _new_parent, **kwargs)
   1082 def __init__(self, spec=None, side_effect=None, return_value=DEFAULT,
   1083              wraps=None, name=None, spec_set=None, parent=None,
   1084              _spec_state=None, _new_name='', _new_parent=None, **kwargs):
   1085     self.__dict__['_mock_return_value'] = return_value
-> 1086     _safe_super(CallableMixin, self).__init__(
   1087         spec, wraps, name, spec_set, parent,
   1088         _spec_state, _new_name, _new_parent, **kwargs
   1089     )
   1091     self.side_effect = side_effect

File ~/.pyenv/versions/3.10.3/lib/python3.10/unittest/mock.py:457, in NonCallableMock.__init__(self, spec, wraps, name, spec_set, parent, _spec_state, _new_name, _new_parent, _spec_as_instance, _eat_self, unsafe, **kwargs)
    454 __dict__['_mock_unsafe'] = unsafe
    456 if kwargs:
--> 457     self.configure_mock(**kwargs)
    459 _safe_super(NonCallableMock, self).__init__(
    460     spec, wraps, name, spec_set, parent,
    461     _spec_state
    462 )

File ~/.pyenv/versions/3.10.3/lib/python3.10/unittest/mock.py:625, in NonCallableMock.configure_mock(self, **kwargs)
    623 obj = self
    624 for entry in args:
--> 625     obj = getattr(obj, entry)
    626 setattr(obj, final, val)

File ~/.pyenv/versions/3.10.3/lib/python3.10/unittest/mock.py:636, in NonCallableMock.__getattr__(self, name)
    634         raise AttributeError("Mock object has no attribute %r" % name)
    635 elif _is_magic(name):
--> 636     raise AttributeError(name)
    637 if not self._mock_unsafe:
    638     if name.startswith(('assert', 'assret', 'asert', 'aseert', 'assrt')):

AttributeError: __len__