Django的查询日期时间为5小时以上年长对象(Django query datetime for

2019-06-24 00:32发布

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我试图写是5个小时以上的老部件Django的查询，我有点失落。 小部件模型具有DateTimeField被填充了widget的创建时间。

Answer 1:

如果Widget是模型的名称，它有一个名为DateTimeField字段属性created ，查询将是： 

from datetime import datetime, timedelta

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

需要注意的是created__lt意味着“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))

这应该够了吧。



Answer 3:

如果settings.USE_TZ = TRUE和settings.TIME_ZONE被设置

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


Answer 4:

最简单的方法已经涵盖其他答案：刚筛选记录其中的日期早五个多小时前。 下面是创建发现至少五秒钟前记录的完整的例子： 

# 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()

这表明我所有，但最后的小工具： 

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

这工作正常，除非你已经启用了时区支持。 在前面的例子中，我这样做，通过改变settings.configure(...看起来像这样： 

settings.configure(
    USE_TZ=True,
    ...

当我这样做，我得到这样的消息： 

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

为了得到一个时区感知日期，使用timezone.now()函数 ，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()

偶尔，在数据库的时钟变得不同步与web服务器的时钟我有问题。 为了避免这样的问题，你可以使用Now()函数来获得数据库的当前时间。 

# 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()

我还没有看到这个问题在最近几年，所以它可能不值得在大多数情况下的麻烦。



文章来源: Django query datetime for objects older than 5 hours
标签： django django-models django-queryset
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