pythonic-equivalence-of-go-struc

from dataclasses import dataclass, field
from typing import List, Dict, Any, Tuple, Type, TypeVar, Mapping, Union
import dacite

T = TypeVar("T")

# reconstruct data by changing data's key to new key from key_referrence in recursion
def _rekey_dict(key_referrence: Mapping, data: Mapping) -> Dict[str, Any]:

    # _rekey_list is a helper function to rekey any sub dicts in list or tuple
    def _rekey_list(key_referrence: Mapping, data: Union[List, Tuple]) -> List:
        res = []
        for v in data:
            if isinstance(v, dict):
                res.append(_rekey_dict(key_referrence, v))
            elif isinstance(v, (List, Tuple)):
                res.append(_rekey_list(key_referrence, v))
            else:
                res.append(v)
        return res

    res = {}
    for k, v in data.items():
        if k in key_referrence:
            new_k = key_referrence[k]
        else:
            new_k = k

        if isinstance(v, dict):
            res[new_k] = _rekey_dict(key_referrence, v)
        elif isinstance(v, (List, Tuple)):
            res[new_k] = _rekey_list(key_referrence, v)
        else:
            res[new_k] = v
    return res


def from_dict(data_class: Type[T], origin_data: dict, metadata_tag: str="") -> T:

    if not metadata_tag:
        return dacite.from_dict(data_class=data_class, data=origin_data)

    # metadata_tag to class field mapping
    tag2field = {}
    for field_name, field_attr in data_class.__dataclass_fields__.items():
        if metadata_tag in field_attr.metadata:
            tag2field[field_attr.metadata[metadata_tag]] = field_name
        else:
            tag2field[field_name] = field_name
    # print(tag2field)

    final_data = _rekey_dict(tag2field, origin_data)
    # print(final_data)
    return dacite.from_dict(data_class=data_class, data=final_data)

@dataclass
class Address:
    street: str = field(default="", metadata={"json_tag": "Street"})
    number: int = field(default=0, metadata={"json_tag": "Number"})


@dataclass
class Person:
    male: bool = field(default=True)
    name: str = field(default="", metadata={"json_tag": "Name"})
    age: int = field(default=0, metadata={"json_tag": "Age"})
    address: List[Address] = field(default_factory=lambda: list(), metadata={"json_tag": "Address"})


if __name__ == "__main__":
    data = {
        "Name": "hh",
        "Age": 10,
        "Address": [{
            "Street": "s1",
            "Number": 99
        }]
    }
    p = from_dict(data_class=Person, metadata_tag="json_tag", origin_data=data)
    print(p) # Person(male=True, name='hh', age=10, address=[Address(street='', number=0)])
    # 在from_dict中构造tag2field的时候目前只能拿到顶层field的metadata
    # Person.address 嵌套的Address类内部字段Street和Number的metadata拿不到，所以`address=[Address(street='', number=0)]`