Python Django 名称错误 : name 'datetime' is not defined

Question

在应用程序目录中的命令行中键入后:

python manage.py runserver

我收到这个错误:

Traceback (most recent call last):
  File "manage.py", line 15, in <module>
    execute_from_command_line(sys.argv)
  File "C:\Users\Paulo\Coding\Python\lib\site-packages\django\core\management\__init__.py", line 371, in execute_from_command_line
    utility.execute()
  File "C:\Users\Paulo\Coding\Python\lib\site-packages\django\core\management\__init__.py", line 347, in execute
    django.setup()
  File "C:\Users\Paulo\Coding\Python\lib\site-packages\django\__init__.py", line 24, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "C:\Users\Paulo\Coding\Python\lib\site-packages\django\apps\registry.py", line 112, in populate
    app_config.import_models()
  File "C:\Users\Paulo\Coding\Python\lib\site-packages\django\apps\config.py", line 198, in import_models
    self.models_module = import_module(models_module_name)
  File "C:\Users\Paulo\Coding\Python\lib\importlib\__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 994, in _gcd_import
  File "<frozen importlib._bootstrap>", line 971, in _find_and_load
  File "<frozen importlib._bootstrap>", line 955, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 665, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 678, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "C:\Users\Paulo\Coding\Django projects\Project 1\freezer\models.py", line 5, in <module>
    class Item(models.Model):
  File "C:\Users\Paulo\Coding\Django projects\Project 1\freezer\models.py", line 31, in Item
    added_date = models.DateField("date added", default=datetime.date.today)
NameError: name 'datetime' is not defined

这个标题类似 question没有帮助我。我有

from datetime import date

在我的 models.py 中。

我正在运行 python 3.6.5 和 Django 2.0.4。我刚才把这个应用程序放到网上，它还在工作，models.py 是相同的。我对自己做错了什么感到困惑。是否与最近必须重置我的 Windows 10 有关？它删除了进程中的 python 安装(在我的程序文件目录中)和许多其他东西。
它单独留下了我的一个 python 安装。我从命令行打开它并导入日期时间并使用该函数返回今天的日期。

这是我的模型.py:

from django.db import models
from django.utils import timezone
from datetime import date

class Item(models.Model):

    FREEZER_DRAWERS = (
            (1, 'Kitchen: Top tray'),
            (2, 'Kitchen: Middle drawer'),
            (3, 'Kitchen: Bottom drawer'),
            )

    TYPES = (
            (1, 'Raw meat'),
            (2, 'Fruit and veg'),
            (3, 'Meal'),
            )

    author = models.ForeignKey('auth.User', on_delete=models.CASCADE)
    title = models.CharField("food", max_length=100)
    item_type = models.IntegerField(choices = TYPES, default = 1)
    added_date = models.DateField("date added", default=datetime.date.today)
    where = models.IntegerField(choices = FREEZER_DRAWERS, default = 1)
    expires_date = models.DateField(default = datetime.date.today)
    on_shopping_list = models.BooleanField()

    def __str__(self):
        return self.title

谢谢!这是多年来我在这些论坛上无法回答的第一个问题!

Answer 1

问题是您没有导入 datetime 模块(或者至少没有以合格的方式导入):您导入了 date 属性。

使用日期类

您可以将 datetime.date 替换为 date(这是您唯一需要的元素):

from django.db import models
from django.utils import timezone
from datetime import <b>date</b>

class Item(models.Model):

    FREEZER_DRAWERS = (
            (1, 'Kitchen: Top tray'),
            (2, 'Kitchen: Middle drawer'),
            (3, 'Kitchen: Bottom drawer'),
            )

    TYPES = (
            (1, 'Raw meat'),
            (2, 'Fruit and veg'),
            (3, 'Meal'),
            )

    author = models.ForeignKey('auth.User', on_delete=models.CASCADE)
    title = models.CharField("food", max_length=100)
    item_type = models.IntegerField(choices = TYPES, default = 1)
    added_date = models.DateField("date added", default=<b>date</b>.today)
    where = models.IntegerField(choices = FREEZER_DRAWERS, default = 1)
    expires_date = models.DateField(default = <b>date</b>.today)
    on_shopping_list = models.BooleanField()

    def __str__(self):
        return self.title

导入模块

或者，您可以导入模块，然后使用 datetime.date:

from django.db import models
from django.utils import timezone
<b>import datetime</b>

class Item(models.Model):

    FREEZER_DRAWERS = (
            (1, 'Kitchen: Top tray'),
            (2, 'Kitchen: Middle drawer'),
            (3, 'Kitchen: Bottom drawer'),
            )

    TYPES = (
            (1, 'Raw meat'),
            (2, 'Fruit and veg'),
            (3, 'Meal'),
            )

    author = models.ForeignKey('auth.User', on_delete=models.CASCADE)
    title = models.CharField("food", max_length=100)
    item_type = models.IntegerField(choices = TYPES, default = 1)
    added_date = models.DateField("date added", default=<b>datetime.date</b>.today)
    where = models.IntegerField(choices = FREEZER_DRAWERS, default = 1)
    expires_date = models.DateField(default = <b>datetime.date</b>.today)
    on_shopping_list = models.BooleanField()

    def __str__(self):
        return self.title

使用 DateField 的 auto_now_add

无论我们如何导入它，事实上 Django 已经支持这样的默认值:使用 auto_now_add=True [Django-doc] : 这将添加一个等于 today 的默认值。此外，它将使字段 blank=True 和 editable=False，以防止它显示在表单等中。所以它不是 完全等同，尽管这可能就是你的意思:

# Note: makes the fields blank=True, and editable=False as well.

from django.db import models
from django.utils import timezone

class Item(models.Model):

    FREEZER_DRAWERS = (
            (1, 'Kitchen: Top tray'),
            (2, 'Kitchen: Middle drawer'),
            (3, 'Kitchen: Bottom drawer'),
            )

    TYPES = (
            (1, 'Raw meat'),
            (2, 'Fruit and veg'),
            (3, 'Meal'),
            )

    author = models.ForeignKey('auth.User', on_delete=models.CASCADE)
    title = models.CharField("food", max_length=100)
    item_type = models.IntegerField(choices = TYPES, default = 1)
    added_date = models.DateField("date added"<b>, auto_now_add=True</b>)
    where = models.IntegerField(choices = FREEZER_DRAWERS, default = 1)
    expires_date = models.DateField(<b>auto_now_add=True</b>)
    on_shopping_list = models.BooleanField()

    def __str__(self):
        return self.title