attrs.asdict（）中缺少列表类型的问题？

Question

I was trying to create a nesting of list() class using Python attrs decoractors, and noticed that the attrs.asdict() did not work at some level of subvariables. Such that:

• attrs.asdict(mlle) displays ok
• attrs.asdict(mlle.list_of_list_of_elements) # FAILS
• attrs.asdict(mlle.list_of_list_of_elements[0]) displays ok

My working example is:

import attr


@attr.s
class MyElement(object):
    element = attr.ib(default="mydefault", type=str)

@attr.s(slots=True)
class MyListOfElements(object):
    one_element = attr.ib(default=attr.Factory(MyElement))
    list_of_elements = attr.ib(default=attr.Factory(list), type=list)
    def add(self, le):
        self.list_of_elements.append(le)

@attr.s(slots=True)
class MyListOfList(object):
    version = attr.ib(default=None, type=str)
    list_of_list_of_elements = attr.ib(default=attr.Factory(list))  # Where's the dunder for this list?

e1 = MyElement("1.1.1.1")
e1_1 = MyElement("11.11.11.11")
le1 = MyListOfElements()
le1.add(e1)
le1.add(e1_1)
print("le1:", le1)

e2 = MyElement("2.2.2.2")
le2 = MyListOfElements(e2)
le2.list_of_elements.append(e2)
print("le2:", le2)

mlle = MyListOfList()
print("mlle:", mlle)
mlle.list_of_list_of_elements.append(le1)
mlle.list_of_list_of_elements.append(le2)
print("mlle:", mlle)

Now onward to using the attr.asdict() function...

# attr.Dict
print("asdict(mlle):", attr.asdict(mlle))
print("asdict(mlle.lle):", attr.asdict(mlle.list_of_list_of_elements))  # FAILS
print("asdict(mlle.lle[0]):", attr.asdict(mlle.list_of_list_of_elements[0]))

I am quite sure that I did something simple incorrectly as I thought I decorated ALL the nested variables with attrs .

I was more perplex that the use of attr.asdict() is not smoothly available at each dotted subvariable such that mlle and mlle.list_of_list_of_elements[0] works, but not the mlle.list_of_list_of_elements in between.

Answer 1

attr.asdict takes an instance of an attr.s -decorated class. mlle and mlle.list_of_list_of_elements[0] are both instances of attr.s -decorated classes. mlle.list_of_list_of_elements is not.