使用資料類包將引數轉換為自定義物件

我最近發現了dataclasses Python 包。在我的型別注釋中使用自定義類時遇到問題。我在下面有一個簡單的例子。

當Entry類被傳遞location引數時，該引數的值應該被用來構造一個Location物件。同樣，當Entry類被傳遞一個字串作為creationDate引數時，它應該被決議（使用dateutil.parser.parse）來創建一個datetime.datetime物件。在我的代碼中，locationandcreationDate引數不會轉換為Locationanddatetime.datetime物件。我不知道如何使這項作業。請指教。

當然，我可以在不使用 dataclasses 包的情況下做到這一點。它將添加更多樣板代碼。我也以此為借口來學習 dataclasses 包，這樣我下次可以更有效地使用它。

試試看

import datetime
import dateutil.parser
import dataclasses
import inspect

@dataclasses.dataclass
class Location():
    latitude: float
    longitude: float

@dataclasses.dataclass
class Entry():
    """
    A single DayOne entry
    """
    creationDate: datetime.datetime = \
        dataclasses.field(default_factory=dateutil.parser.parse)
    location: Location = None

    @classmethod
    def factory(cls, **kwargs):
        class_fields = {k:v for k,v in kwargs.items()
                        if k in inspect.signature(cls).parameters}

        return cls(**class_fields)

if __name__ == "__main__":
    print("Converting from dayone to jekyll\n")


    args = {
        "creationDate": '2022-05-30T04:44:33Z',
        "location": {
            'latitude': -37.8721,
            'longitude': 175.6829,
            'named': 'Hobbiton'
        },
        "text": "In a hole in the ground there lived a hobbit. Not a nasty, dirty, wet hole, filled with the ends of worms and an oozy smell, nor yet a dry, bare, sandy hole with nothing in it to sit down on or to eat: it was a hobbit-hole, and that means comfort."
    }

    entry = Entry.factory(**args)
    print(type(entry.location))
    print(type(entry.creationDate))

uj5u.com熱心網友回復：

一種選擇是使用dataclass-wizard，它比pydantic. 它對早期的 python 版本使用typing-extensions模塊，但在 3.10 中它只依賴于核心 python stdlib。

用法：

from __future__ import annotations  # can be removed in 3.10 

import datetime
# import dateutil.parser
import dataclasses
from pprint import pprint

from dataclass_wizard import JSONWizard


@dataclasses.dataclass
class Location:
    latitude: float
    longitude: float
    named: str | None = None


@dataclasses.dataclass
class Entry(JSONWizard):
    """
    A single DayOne entry
    """
    creation_date: datetime.datetime
    location: Location | None = None


if __name__ == "__main__":
    print("Converting from dayone to jekyll\n")

    args = {
        "creationDate": '2022-05-30T04:44:33Z',
        "location": {
            'latitude': -37.8721,
            'longitude': 175.6829,
            'named': 'Hobbiton'
        },
        "text": "In a hole in the ground there lived a hobbit. Not a nasty, dirty, wet hole, filled with the ends of worms and an oozy smell, nor yet a dry, bare, sandy hole with nothing in it to sit down on or to eat: it was a hobbit-hole, and that means comfort."
    }

    entry = Entry.from_dict(args)
    print(type(entry.location))
    print(type(entry.creation_date))
    print()

    print('Object:')
    pprint(entry)

結果：

Converting from dayone to jekyll

<class '__main__.Location'>
<class 'datetime.datetime'>

Object:
Entry(creation_date=datetime.datetime(2022, 5, 30, 4, 44, 33, tzinfo=datetime.timezone.utc),
      location=Location(latitude=-37.8721, longitude=175.6829, named='Hobbiton'))

旁注：我實際上并沒有想過用它dateutil.parser.parse來決議日期字串，盡管這可能是一個好主意。當前的實作使用datetime.fromisoformat在一般用例中運行良好。

標籤：Python 目的 蟒蛇日期时间 蟒蛇数据类

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