Question

当我向模型添加DateField时，有时会弹出一个问题。我相信当我将一个Date字段添加到已经包含数据的表时会发生这种情况。问题是我无法使错误消失。每次我运行迁移时都会出现错误TypeError: expected string or buffer

有没有办法强制迁移。它甚至发生在我从模型中删除字段，删除数据库和删除迁移之后。我还尝试手动输入数据库中的日期戳。

我可以解决的唯一方法是创建一个新项目并复制代码。

我将创建和last_modified添加到了错误的模型

class Entry(models.Model):
    title = models.CharField(max_length=50, blank=True, null=True)
    start = models.DateField(blank=True, null=True)
    end = models.DateField(blank=True, null=True)

    creation = models.DateField(auto_now_add=True)
    last_modified = models.DateField(auto_now=True)

    def __unicode__(self):
        return self.title

我已经恢复到它工作的时候了。

class Entry(models.Model):
    title = models.CharField(max_length=50, blank=True, null=True)
    start = models.DateField(blank=True, null=True)
    end = models.DateField(blank=True, null=True)

    def __unicode__(self):
        return self.title

完全错误：

  File "manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/Users/User/pyProjects/projects/Folder/Env/lib/python2.7/site-packages/django/core/management/__init__.py", line 338, in execute_from_command_line
    utility.execute()
  File "/Users/User/pyProjects/projects/Folder/Env/lib/python2.7/site-packages/django/core/management/__init__.py", line 330, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/Users/User/pyProjects/projects/Folder/Env/lib/python2.7/site-packages/django/core/management/base.py", line 393, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/Users/User/pyProjects/projects/Folder/Env/lib/python2.7/site-packages/django/core/management/base.py", line 444, in execute
    output = self.handle(*args, **options)
  File "/Users/User/pyProjects/projects/Folder/Env/lib/python2.7/site-packages/django/core/management/commands/migrate.py", line 222, in handle
    executor.migrate(targets, plan, fake=fake, fake_initial=fake_initial)
  File "/Users/User/pyProjects/projects/Folder/Env/lib/python2.7/site-packages/django/db/migrations/executor.py", line 110, in migrate
    self.apply_migration(states[migration], migration, fake=fake, fake_initial=fake_initial)
  File "/Users/User/pyProjects/projects/Folder/Env/lib/python2.7/site-packages/django/db/migrations/executor.py", line 148, in apply_migration
    state = migration.apply(state, schema_editor)
  File "/Users/User/pyProjects/projects/Folder/Env/lib/python2.7/site-packages/django/db/migrations/migration.py", line 115, in apply
    operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
  File "/Users/User/pyProjects/projects/Folder/Env/lib/python2.7/site-packages/django/db/migrations/operations/fields.py", line 62, in database_forwards
    field,
  File "/Users/User/pyProjects/projects/Folder/Env/lib/python2.7/site-packages/django/db/backends/sqlite3/schema.py", line 179, in add_field
    self._remake_table(model, create_fields=[field])
  File "/Users/User/pyProjects/projects/Folder/Env/lib/python2.7/site-packages/django/db/backends/sqlite3/schema.py", line 77, in _remake_table
    self.effective_default(field)
  File "/Users/User/pyProjects/projects/Folder/Env/lib/python2.7/site-packages/django/db/backends/base/schema.py", line 211, in effective_default
    default = field.get_db_prep_save(default, self.connection)
  File "/Users/User/pyProjects/projects/Folder/Env/lib/python2.7/site-packages/django/db/models/fields/__init__.py", line 710, in get_db_prep_save
    prepared=False)
  File "/Users/User/pyProjects/projects/Folder/Env/lib/python2.7/site-packages/django/db/models/fields/__init__.py", line 1322, in get_db_prep_value
    value = self.get_prep_value(value)
  File "/Users/User/pyProjects/projects/Folder/Env/lib/python2.7/site-packages/django/db/models/fields/__init__.py", line 1317, in get_prep_value
    return self.to_python(value)
  File "/Users/User/pyProjects/projects/Folder/Env/lib/python2.7/site-packages/django/db/models/fields/__init__.py", line 1274, in to_python
    parsed = parse_date(value)
  File "/Users/User/pyProjects/projects/Folder/Env/lib/python2.7/site-packages/django/utils/dateparse.py", line 60, in parse_date
    match = date_re.match(value)
TypeError: expected string or buffer

Answer 1

auto_now和auto_now_add过去曾导致迁移问题，最好的方法是使用默认字段。

from django.utils import timezone

class Entry(models.Model):
    title = models.CharField(max_length=50, blank=True, null=True)
    start = models.DateField(blank=True, null=True)
    end = models.DateField(blank=True, null=True)

    creation = models.DateField(default=timezone.now())
    last_modified = models.DateField(default=timezone.now())

    def __unicode__(self):
        return self.title

我使用时区模块，如果你的项目是时区感知的话，这是首选。

Answer 2

如果@petkostas的解决方案无效，请尝试使用 str 代替 unicode

示例：

def __str__(self):
        return self.title

Django TypeError：期望的字符串或缓冲区

2 个答案: