django.core.exceptions.ValidationError: ["'' value has an invalid date format. It must be in YYYY-MM-DD format."]

Question

我使用 Django 版本 2.0.7 并尝试创建一个日期模块字段，直到遇到此错误：

Date = models.DateField(blank=True, default='', null=True, help_text='today date.')

我之前使用过此代码并且它有效但现在在 python manage.py makemigrations 我使用 python manage.py migrate 之后我遇到了这个错误。完整日志：

Operations to perform:
  Apply all migrations: Blog, Portfolio, admin, auth, contenttypes, sessions
Running migrations:
  Applying Blog.0002_auto_20180728_0218...Traceback (most recent call last):
  File "manage.py", line 15, in <module>
    execute_from_command_line(sys.argv)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\core\management\__init__.py", line 371, in execute_from_command_line
    utility.execute()
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\core\management\__init__.py", line 365, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\core\management\base.py", line 288, in run_from_argv
    self.execute(*args, **cmd_options)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\core\management\base.py", line 335, in execute
    output = self.handle(*args, **options)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\core\management\commands\migrate.py", line 200, in handle
    fake_initial=fake_initial,
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\db\migrations\executor.py", line 117, in migrate
    state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\db\migrations\executor.py", line 147, in _migrate_all_forwards
    state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\db\migrations\executor.py", line 244, in apply_migration
    state = migration.apply(state, schema_editor)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\db\migrations\migration.py", line 122, in apply
    operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\db\migrations\operations\fields.py", line 216, in database_forwards
    schema_editor.alter_field(from_model, from_field, to_field)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\db\backends\base\schema.py", line 525, in alter_field
    old_db_params, new_db_params, strict)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\db\backends\postgresql\schema.py", line 122, in _alter_field
    new_db_params, strict,
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\db\backends\base\schema.py", line 629, in _alter_field
    old_default = self.effective_default(old_field)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\db\backends\base\schema.py", line 240, in effective_default
    default = field.get_db_prep_save(default, self.connection)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\db\models\fields\__init__.py", line 767, in get_db_prep_save
    return self.get_db_prep_value(value, connection=connection, prepared=False)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\db\models\fields\__init__.py", line 1276, in get_db_prep_value
    value = self.get_prep_value(value)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\db\models\fields\__init__.py", line 1271, in get_prep_value
    return self.to_python(value)
  File "D:\Learn\Projects\Django\myvenv\lib\site-packages\django\db\models\fields\__init__.py", line 1246, in to_python
    params={'value': value},
django.core.exceptions.ValidationError: ["'' value has an invalid date format. It must be in YYYY-MM-DD format."]

我什至尝试删除所有迁移和数据库并进行新的迁移，但它也不起作用。这个 link 对我也不起作用：

另外，很抱歉我的问题写错了

Answer 1

默认不能为空字符串，因为那不是日期。例如，在模式页面中使用 date(1111, 11, 11) 和 from datetime import date 然后如果你会得到同样的错误，你必须删除所有迁移和擦除你的数据库数据并且做迁移又是。

Answer 2

import datetime

import pytz
from django.apps import AppConfig
from django.db.models.fields import DateTimeField
from django.utils.dateparse import parse_date
from django.core.exceptions import ValidationError

default_app_config = 'patch.PatchConfig'


def patch():
    def get_db_prep_value(self, value, connection, prepared=False):
        if isinstance(value, str):
            if not value:
                value = None
            elif not parse_date(value):
                try:
                    value = datetime.datetime.fromtimestamp(int(value)).replace(tzinfo=pytz.UTC)
                except:
                    raise ValidationError(
                        self.error_messages['invalid'],
                        code='invalid',
                        params={'value': value},
                    )
        if not prepared:
            value = self.get_prep_value(value)
        return connection.ops.adapt_datetimefield_value(value)

    DateTimeField.get_db_prep_value = get_db_prep_value


class PatchConfig(AppConfig):
    name = 'patch'

    def ready(self):
        patch()

您可能需要这个补丁

Answer 3

我在更新 model.py

时遇到同样的格式错误

我给你看我的场景，也许它会有所帮助。所以我有一个现有的 class 并想添加这一行：

time = models.TimeField()

比我做的 makemigrations 现在重要的部分

Please select a fix:
1) Provide a one-off default now (will be set on all existing rows with a null value
for this column)
2) Quit, and let me add a default in models.py

选择 1) 并键入 timezone.now 以设置默认值 -- 迁移，你明白了

django.core.exceptions.ValidationError: ["'' value has an invalid date format. It must be in YYYY-MM-DD format."]

django.core.exceptions.ValidationError: ["'' value has an invalid date format. It must be in YYYY-MM-DD format."]

django

python-3.x

django-models

django-templates

datefield