Django查询超过5小时的对象的日期时间

Question

我正在尝试为超过5个小时的小部件编写一个Django查询，我有点迷失了。窗口小部件模型具有DateTimeField，其中填充了窗口小部件的创建时间。

Answer 1

如果Widget是模型的名称，并且它具有名为created的DateTimeField属性，则查询将为：

from datetime import datetime, timedelta

time_threshold = datetime.now() - timedelta(hours=5)
results = Widget.objects.filter(created__lt=time_threshold)

请注意created__lt表示“已创建小于”。

Answer 2

now = datetime.datetime.now()
earlier = now - datetime.timedelta(hours=5)
MyModel.objects.filter(my_date_field__range=(earlier,now))

这应该可以解决问题。

Answer 3

如果settings.USE_TZ = True和settings.TIME_ZONE正在设置

from django.utils import timezone
five_h_ago = timezone.now()-timezone.timedelta(hours=5)
example.object.filter(datetimefield__lt=five_h_ago)

Answer 4

其他答案已经涵盖了最简单的方法：仅过滤日期早于五个小时前的记录。这是一个完整的示例，可查找至少五秒钟前创建的记录：

# Tested with Django 1.11.15 and Python 3.6.
import logging
import sys
from datetime import datetime, timedelta
from time import sleep

import django
from django.apps import apps
from django.apps.config import AppConfig
from django.conf import settings
from django.db import connections, models, DEFAULT_DB_ALIAS
from django.db.models.base import ModelBase

NAME = 'udjango'
DB_FILE = NAME + '.db'


def main():
    setup()
    logger = logging.getLogger(__name__)

    class Widget(models.Model):
        name = models.CharField(max_length=200)
        date_created = models.DateTimeField(auto_now_add=True)

        def __str__(self):
            return self.name

    syncdb(Widget)

    Widget.objects.create(name='spline')
    sleep(1)
    Widget.objects.create(name='reticulator')
    sleep(1)
    Widget.objects.create(name='tardis')
    sleep(5)
    Widget.objects.create(name='sonic screwdriver')
    sleep(1)

    cutoff_time = datetime.now() - timedelta(seconds=5)
    for widget in Widget.objects.filter(date_created__lt=cutoff_time):
        logger.info(widget.name)


def setup():
    with open(DB_FILE, 'w'):
        pass  # wipe the database
    settings.configure(
        DEBUG=True,
        DATABASES={
            DEFAULT_DB_ALIAS: {
                'ENGINE': 'django.db.backends.sqlite3',
                'NAME': DB_FILE}},
        LOGGING={'version': 1,
                 'disable_existing_loggers': False,
                 'formatters': {
                    'debug': {
                        'format': '[%(levelname)s]'
                                  '%(name)s.%(funcName)s(): %(message)s',
                        'datefmt': '%Y-%m-%d %H:%M:%S'}},
                 'handlers': {
                    'console': {
                        'level': 'DEBUG',
                        'class': 'logging.StreamHandler',
                        'formatter': 'debug'}},
                 'root': {
                    'handlers': ['console'],
                    'level': 'INFO'},
                 'loggers': {
                    "django.db": {"level": "INFO"}}})
    app_config = AppConfig(NAME, sys.modules['__main__'])
    apps.populate([app_config])
    django.setup()
    original_new_func = ModelBase.__new__

    @staticmethod
    def patched_new(cls, name, bases, attrs):
        if 'Meta' not in attrs:
            class Meta:
                app_label = NAME
            attrs['Meta'] = Meta
        return original_new_func(cls, name, bases, attrs)
    ModelBase.__new__ = patched_new


def syncdb(model):
    """ Standard syncdb expects models to be in reliable locations.

    Based on https://github.com/django/django/blob/1.9.3
    /django/core/management/commands/migrate.py#L285
    """
    connection = connections[DEFAULT_DB_ALIAS]
    with connection.schema_editor() as editor:
        editor.create_model(model)


main()

除最后一个小部件外，所有内容都显示给我：

[INFO]__main__.main(): spline
[INFO]__main__.main(): reticulator
[INFO]__main__.main(): tardis

那很好，除非您启用了时区支持。在上一个示例中，我通过将settings.configure(...更改为以下形式来做到这一点：

settings.configure(
    USE_TZ=True,
    ...

当我这样做时，会收到如下消息：

RuntimeWarning: DateTimeField Widget.date_created received a naive datetime (2019-01-07 16:39:04.563563) while time zone support is active.

要获取可识别时区的日期，请使用timezone.now() function而不是datetime.now()：

# Tested with Django 1.11.15 and Python 3.6.
import logging
import sys
from datetime import timedelta
from time import sleep

import django
from django.apps import apps
from django.apps.config import AppConfig
from django.conf import settings
from django.db import connections, models, DEFAULT_DB_ALIAS
from django.db.models.base import ModelBase
from django.utils import timezone

NAME = 'udjango'
DB_FILE = NAME + '.db'


def main():
    setup()
    logger = logging.getLogger(__name__)

    class Widget(models.Model):
        name = models.CharField(max_length=200)
        date_created = models.DateTimeField(auto_now_add=True)

        def __str__(self):
            return self.name

    syncdb(Widget)

    Widget.objects.create(name='spline')
    sleep(1)
    Widget.objects.create(name='reticulator')
    sleep(1)
    Widget.objects.create(name='tardis')
    sleep(5)
    Widget.objects.create(name='sonic screwdriver')
    sleep(1)

    cutoff_time = timezone.now() - timedelta(seconds=5)
    for widget in Widget.objects.filter(date_created__lt=cutoff_time):
        logger.info(widget.name)


def setup():
    with open(DB_FILE, 'w'):
        pass  # wipe the database
    settings.configure(
        USE_TZ=True,
        DEBUG=True,
        DATABASES={
            DEFAULT_DB_ALIAS: {
                'ENGINE': 'django.db.backends.sqlite3',
                'NAME': DB_FILE}},
        LOGGING={'version': 1,
                 'disable_existing_loggers': False,
                 'formatters': {
                    'debug': {
                        'format': '[%(levelname)s]'
                                  '%(name)s.%(funcName)s(): %(message)s',
                        'datefmt': '%Y-%m-%d %H:%M:%S'}},
                 'handlers': {
                    'console': {
                        'level': 'DEBUG',
                        'class': 'logging.StreamHandler',
                        'formatter': 'debug'}},
                 'root': {
                    'handlers': ['console'],
                    'level': 'INFO'},
                 'loggers': {
                    "django.db": {"level": "INFO"}}})
    app_config = AppConfig(NAME, sys.modules['__main__'])
    apps.populate([app_config])
    django.setup()
    original_new_func = ModelBase.__new__

    @staticmethod
    def patched_new(cls, name, bases, attrs):
        if 'Meta' not in attrs:
            class Meta:
                app_label = NAME
            attrs['Meta'] = Meta
        return original_new_func(cls, name, bases, attrs)
    ModelBase.__new__ = patched_new


def syncdb(model):
    """ Standard syncdb expects models to be in reliable locations.

    Based on https://github.com/django/django/blob/1.9.3
    /django/core/management/commands/migrate.py#L285
    """
    connection = connections[DEFAULT_DB_ALIAS]
    with connection.schema_editor() as editor:
        editor.create_model(model)


main()

有时，我遇到了数据库时钟与Web服务器时钟不同步的问题。为了避免这种问题，您可以使用Now() function来获取数据库中的当前时间。

# Tested with Django 1.11.15 and Python 3.6.
import logging
import sys
from datetime import timedelta
from time import sleep

import django
from django.apps import apps
from django.apps.config import AppConfig
from django.conf import settings
from django.db import connections, models, DEFAULT_DB_ALIAS
from django.db.models.base import ModelBase
from django.db.models.functions import Now
from django.utils import timezone

NAME = 'udjango'
DB_FILE = NAME + '.db'


def main():
    setup()
    logger = logging.getLogger(__name__)

    class Widget(models.Model):
        name = models.CharField(max_length=200)
        date_created = models.DateTimeField()

        def __str__(self):
            return self.name

    syncdb(Widget)

    Widget.objects.create(name='spline', date_created=Now())
    sleep(1)
    Widget.objects.create(name='reticulator', date_created=Now())
    sleep(1)
    Widget.objects.create(name='tardis', date_created=Now())
    sleep(5)
    Widget.objects.create(name='sonic screwdriver', date_created=Now())
    sleep(1)

    cutoff_time = Now() - timedelta(seconds=5)
    for widget in Widget.objects.filter(date_created__lt=cutoff_time):
        logger.info(widget.name)


def setup():
    with open(DB_FILE, 'w'):
        pass  # wipe the database
    settings.configure(
        USE_TZ=True,
        DEBUG=True,
        DATABASES={
            DEFAULT_DB_ALIAS: {
                'ENGINE': 'django.db.backends.sqlite3',
                'NAME': DB_FILE}},
        LOGGING={'version': 1,
                 'disable_existing_loggers': False,
                 'formatters': {
                    'debug': {
                        'format': '[%(levelname)s]'
                                  '%(name)s.%(funcName)s(): %(message)s',
                        'datefmt': '%Y-%m-%d %H:%M:%S'}},
                 'handlers': {
                    'console': {
                        'level': 'DEBUG',
                        'class': 'logging.StreamHandler',
                        'formatter': 'debug'}},
                 'root': {
                    'handlers': ['console'],
                    'level': 'INFO'},
                 'loggers': {
                    "django.db": {"level": "INFO"}}})
    app_config = AppConfig(NAME, sys.modules['__main__'])
    apps.populate([app_config])
    django.setup()
    original_new_func = ModelBase.__new__

    @staticmethod
    def patched_new(cls, name, bases, attrs):
        if 'Meta' not in attrs:
            class Meta:
                app_label = NAME
            attrs['Meta'] = Meta
        return original_new_func(cls, name, bases, attrs)
    ModelBase.__new__ = patched_new


def syncdb(model):
    """ Standard syncdb expects models to be in reliable locations.

    Based on https://github.com/django/django/blob/1.9.3
    /django/core/management/commands/migrate.py#L285
    """
    connection = connections[DEFAULT_DB_ALIAS]
    with connection.schema_editor() as editor:
        editor.create_model(model)


main()

近年来，我还没有看到这个问题，所以在大多数情况下，这不值得麻烦。

Answer 5

如果您希望早于5个小时，请使用created__gte代替created__lt