将嵌套的 Python 对象转换为字典的最经济的方法是什么？

Question

I have some SQLAlchemy objects which contain lists of more SQLAlchemy objects, and so on (for about 5 levels). I wish to convert all the objects to dictionaries.

I can convert an object to a dictionary by using the __dict__ property, no problem. However, I'm having trouble figuring out the best way to convert all the nested objects as well, without having to do each level explicitly.

So far, this is the best I can come up with, but it doesn't recurse properly. It basically breaks after one pass, so there's clearly something wrong with my logic. Can you see what's wrong with it??

I am hoping to do:

all_dict = myDict(obj.__dict__)

def myDict(d):
    for k,v in d.items():
        if isinstance(v,list):
            d[k] = [myDict(i.__dict__) for i in v]
        else:
            d[k] = v
    return d

Answer 1

Life Hack:

def to_dict(obj):
    return json.loads(json.dumps(obj, default=lambda o: o.__dict__))

This leverages the default input of the json.dumps() method (or json.dump() ) by returning the __dict__ representation of the objects that are not serializable. Note that this may not work when objects contain non-standard data structures (such as NumPy or Pandas). The following is the description from the documentation of json.dump :

If specified, default should be a function that gets called for objects that can't otherwise be serialized. It should return a JSON encodable version of the object or raise a TypeError. If not specified, TypeError is raised.

Answer 2

I am not sure if I understood exactly what you want - but if I got, this function can do what you want: It does search recursively on an object's attributes, yielding a nested dictionary + list structure, with the ending points being python objects not having a __dict__ attribute - which in SQLAlchemy's case are likely to be basic Python types like numbers and strings. (If that fails, replacing the "hasattr dict" test for soemthing more sensible should fix the code for your needs.

def my_dict(obj):
    if not  hasattr(obj,"__dict__"):
        return obj
    result = {}
    for key, val in obj.__dict__.items():
        if key.startswith("_"):
            continue
        element = []
        if isinstance(val, list):
            for item in val:
                element.append(my_dict(item))
        else:
            element = my_dict(val)
        result[key] = element
    return result