问题描述
我正在尝试学习django，更改模型时会出错。我尝试了很多类似default = datetime.datetime.now的尝试，但我不知道如何解决。
I'm trying to learn django and error occur in changing models. I tried a lot like default=datetime.datetime.now but I dont know how to fix it.
这些是我的模型
导入日期时间
from django.db import modelsimport datetime
class Candidate(models.Model):
name = models.CharField(max_length=10)
introduction = models.TextField()
area = models.CharField(max_length=15)
party_number=models.IntegerField(default=0)
def __str__(self) :
return self.name
class Poll(models.Model) :
start_date = models.DateTimeField()
end_date = models.DateTimeField()
area = models.CharField(max_length=15)
class Choice(models.Model) :
poll = models.ForeignKey(Poll)
candidate = models.ForeignKey(Candidate)
votes = models.IntegerField(default=0)
当我输入commmand时： python manage.py migration ，发生此错误
when I type commmand : python manage.py migrate, this error occured
Operations to perform:
Apply all migrations: admin, ang, auth, contenttypes, sessions
Running migrations:
Applying ang.0003_poll_end_date...Traceback (most recent call last):
File "manage.py", line 22, in <module>
execute_from_command_line(sys.argv)
File "C:\Python\Python35-32\lib\site-packages\django\core\management\__init__.py", line 367, in execute_from_command_line
utility.execute()
File "C:\Python\Python35-32\lib\site-packages\django\core\management\__init__.py", line 359, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "C:\Python\Python35-32\lib\site-packages\django\core\management\base.py", line 294, in run_from_argv
self.execute(*args, **cmd_options)
File "C:\Python\Python35-32\lib\site-packages\django\core\management\base.py", line 345, in execute
output = self.handle(*args, **options)
File "C:\Python\Python35-32\lib\site-packages\django\core\management\commands\migrate.py", line 204, in handle
fake_initial=fake_initial,
File "C:\Python\Python35-32\lib\site-packages\django\db\migrations\executor.py", line 115, in migrate
state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial)
File "C:\Python\Python35-32\lib\site-packages\django\db\migrations\executor.py", line 145, in _migrate_all_forwards
state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
File "C:\Python\Python35-32\lib\site-packages\django\db\migrations\executor.py", line 244, in apply_migration
state = migration.apply(state, schema_editor)
File "C:\Python\Python35-32\lib\site-packages\django\db\migrations\migration.py", line 129, in apply
operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
File "C:\Python\Python35-32\lib\site-packages\django\db\migrations\operations\fields.py", line 84, in database_forwards
field,
File "C:\Python\Python35-32\lib\site-packages\django\db\backends\sqlite3\schema.py", line 231, in add_field
self._remake_table(model, create_fields=[field])
File "C:\Python\Python35-32\lib\site-packages\django\db\backends\sqlite3\schema.py", line 113, in _remake_table
self.effective_default(field)
File "C:\Python\Python35-32\lib\site-packages\django\db\backends\base\schema.py", line 221, in effective_default
default = field.get_db_prep_save(default, self.connection)
File "C:\Python\Python35-32\lib\site-packages\django\db\models\fields\__init__.py", line 755, in get_db_prep_save
prepared=False)
File "C:\Python\Python35-32\lib\site-packages\django\db\models\fields\__init__.py", line 1438, in get_db_prep_value
value = self.get_prep_value(value)
File "C:\Python\Python35-32\lib\site-packages\django\db\models\fields\__init__.py", line 1417, in get_prep_value
value = super(DateTimeField, self).get_prep_value(value)
File "C:\Python\Python35-32\lib\site-packages\django\db\models\fields\__init__.py", line 1275, in get_prep_value
return self.to_python(value)
File "C:\Python\Python35-32\lib\site-packages\django\db\models\fields\__init__.py", line 1378, in to_python
parsed = parse_datetime(value)
File "C:\Python\Python35-32\lib\site-packages\django\utils\dateparse.py", line 93, in parse_datetime
match = datetime_re.match(value)
TypeError: expected string or bytes-like object
请帮助我！
推荐答案
如果修改了模型中的字段。之后，您在那时运行makemigrations，就这样询问
If you modified the fields in models. after that you run makemigrations that time it asking like this
^C(api_env)nyros@nyros:~/Desktop/santhi_projects/sample_api/sample_api$ python manage.py makemigrations
You are trying to add a non-nullable field 'provider' to content without a default; we can't do that (the database needs something to populate existing rows).
Please select a fix:
1) Provide a one-off default now (will be set on all existing rows)
2) Quit, and let me add a default in models.py
Select an option: 1
我们选择1个选项，它将显示如下
We select 1 option, then it will display like this
Please enter the default value now, as valid Python
The datetime and django.utils.timezone modules are available, so you can do e.g. timezone.now()
>>> timezone.now()
我们给定timezone.now（）然后完成迁移。
We given timezone.now() then makemigrations completed.
查看迁移的最后一个文件，有
See your migrations last file, there is
class Migration(migrations.Migration):
dependencies = [
migrations.swappable_dependency(settings.AUTH_USER_MODEL),
('providers', '0023_remove_content_provider'),
]
operations = [
migrations.AddField(
model_name='content',
name='provider',
field=models.ForeignKey(related_name='library', default=datetime.datetime(2016, 11, 1, 7, 15, 12, 655838, tzinfo=utc), to=settings.AUTH_USER_MODEL),
preserve_default=False,
),
]
在上面的代码中，请注意以下行
In above code observe this line
default=datetime.datetime(2016, 11, 1, 7, 15, 12, 655838, tzinfo=utc)
在那一行中，forgeinkey字段的默认值为datetime，是否为正确值？
In that line forgeinkey field default value is datetime, Is it correct value?
否，因此您必须为该字段提供默认的字符串或对象。
No, so you have to give some string or object is a default value to that field.
现在，您必须在相应的迁移文件中编辑该值，例如
Now you have to edit that value in that corresponding migration file, like this
default='some string'
然后保存并运行迁移命令。
then save and run the migrate command.
尝试并让我知道，是否有效。谢谢
Try and let me know, Is it works or not.Thanks
这篇关于Django迁移错误：TypeError预期的字符串或类似字节的对象的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！