如何用Nanoseconds对象替换Python DateTimes中的datetime字段

Question

在Python中，我需要在google cloud firestore文档中设置时间戳字段

我知道firestore时间戳字段应该使用google.api_core.datetime_helpers.DatetimeWithNanoseconds设置，它是Datetime的一个子类

我需要用一个指定的分钟字段设置now（）时间戳，并在下面给出的特定时间拨回它

                'cursor_specs' = {
                    # specs to construct the next cursor
                    'minute_tick': 0,
                    'hours_dial_back': 1,
                },

因为DatetimeWithNanoseconds是Datetime的一个子类，据说继承了它的所有函数，所以我尝试使用now（）和replace（）直接使用DatetimeWithNanoseconds

from google.api_core.datetime_helpers import DatetimeWithNanoseconds

time_cursor = DatetimeWithNanoseconds.now().replace(minute=cursor_specs['minute_tick'],
                                    second=0, microsecond=0
                                ) - timedelta(hours=cursor_specs['hours_dial_back']

fs_model = fs.document(model["name"]).set({'time_cursor': time_cursor})

它失败了，出现了一个错误

  File "/usr/local/lib/python3.8/site-packages/google/cloud/firestore_v1/_helpers.py", line 219, in <dictcomp>
    return {key: encode_value(value) for key, value in values_dict.items()}
  File "/usr/local/lib/python3.8/site-packages/google/cloud/firestore_v1/_helpers.py", line 173, in encode_value
    return document.Value(timestamp_value=value.timestamp_pb())
  File "/usr/local/lib/python3.8/site-packages/google/api_core/datetime_helpers.py", line 271, in timestamp_pb
    nanos = self._nanosecond or self.microsecond * 1000
AttributeError: _nanosecond

Answer 1

我贴出这个问题是因为我很难回答，所以我希望我的发现能帮助其他人

我找到的最佳解决方案是使用now（）和replace（）首先设置一个常规的Datetime对象，然后将其转换为DatetimeWithNanoseconds对象

from google.api_core.datetime_helpers import DatetimeWithNanoseconds
from google.api_core.datetime_helpers import to_rfc3339

time_cursor_in_datetime = datetime.now().replace(
                                minute=model['cursor']['next']['minute_tick'],
                                second=0, microsecond=0
                            ) - timedelta(hours=model['cursor']['next']['hours_dial_back'])

time_cursor =  DatetimeWithNanoseconds.from_rfc3339(
                                to_rfc3339(time_cursor_in_datetime)
                            )


fs_model = fs.document(model["name"]).set({'time_cursor': time_cursor})