Django 2中的迁移错误；AttributeError: 'str' object has no attribute 'decode'。

Question

我正在为我的新应用程序'core'运行迁移。

当我对它进行迁移时，出现了一个告诉我以下信息的错误;

query = query.decode(errors='replace')
AttributeError: 'str' object has no attribute 'decode'

I am posting the Traceback below;

C> python manage.py makemigrations core
Traceback (most recent call last):
  File "manage.py", line 21, in <module>
    main()
  File "manage.py", line 17, in main
    execute_from_command_line(sys.argv)
  File "C:\Python37\lib\site-packages\django\core\management\__init__.py", line 381, in execute_from_command_line
    utility.execute()
  File "C:\Python37\lib\site-packages\django\core\management\__init__.py", line 375, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "C:\Python37\lib\site-packages\django\core\management\base.py", line 323, in run_from_argv
    self.execute(*args, **cmd_options)
  File "C:\Python37\lib\site-packages\django\core\management\base.py", line 364, in execute
    output = self.handle(*args, **options)
  File "C:\Python37\lib\site-packages\django\core\management\base.py", line 83, in wrapped
    res = handle_func(*args, **kwargs)
  File "C:\Python37\lib\site-packages\django\core\management\commands\makemigrations.py", line 101, in handle
    loader.check_consistent_history(connection)
  File "C:\Python37\lib\site-packages\django\db\migrations\loader.py", line 283, in check_consistent_history
    applied = recorder.applied_migrations()
  File "C:\Python37\lib\site-packages\django\db\migrations\recorder.py", line 73, in applied_migrations
    if self.has_table():
  File "C:\Python37\lib\site-packages\django\db\migrations\recorder.py", line 56, in has_table
    return self.Migration._meta.db_table in self.connection.introspection.table_names(self.connection.cursor())
  File "C:\Python37\lib\site-packages\django\db\backends\base\base.py", line 256, in cursor
    return self._cursor()
  File "C:\Python37\lib\site-packages\django\db\backends\base\base.py", line 233, in _cursor
    self.ensure_connection()
  File "C:\Python37\lib\site-packages\django\db\backends\base\base.py", line 217, in ensure_connection
    self.connect()
  File "C:\Python37\lib\site-packages\django\db\backends\base\base.py", line 197, in connect
    self.init_connection_state()
  File "C:\Python37\lib\site-packages\django\db\backends\mysql\base.py", line 233, in init_connection_state
    if self.features.is_sql_auto_is_null_enabled:
  File "C:\Python37\lib\site-packages\django\utils\functional.py", line 80, in __get__
    res = instance.__dict__[self.name] = self.func(instance)
  File "C:\Python37\lib\site-packages\django\db\backends\mysql\features.py", line 82, in is_sql_auto_is_null_enabled
    cursor.execute('SELECT @@SQL_AUTO_IS_NULL')
  File "C:\Python37\lib\site-packages\django\db\backends\utils.py", line 103, in execute
    sql = self.db.ops.last_executed_query(self.cursor, sql, params)
  File "C:\Python37\lib\site-packages\django\db\backends\mysql\operations.py", line 146, in last_executed_query
    query = query.decode(errors='replace')
AttributeError: 'str' object has no attribute 'decode'

以下是 Models 文件：

    class Movie(models.Model):

    NOT_RATED = 0
    RATED_G = 1
    RATED_PG = 2
    RATED_R = 3

    RATINGS = (
        (NOT_RATED,'NR - Not Rated'),
        (RATED_G, 'G - General Audiences'),
        (RATED_PG, 'PG - Parental Guidance'),
        (RATED_R, 'R - Restricted'),
        )

    title = models.CharField(max_length=140)
    plot = models.TextField()
    year = models.PositiveIntegerField()
    rating = models.IntegerField(choices=RATINGS, default=NOT_RATED)
    runtime = models.PositiveIntegerField()
    website = models.URLField(blank=True)

    def __str__(self):
        return '{} {}'.format(self.title, self.year)

这是我使用的数据库（MySQL）的设置：

    DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': 'mymdb',
        'USER': '',
        'PASSWORD': '',
        'HOST': '127.0.0.1',
        'PORT': '3306'
    }
}

- obadul024

---

看起来是Python2的代码，可以使用str.decode()。 - furas

但我正在使用Python 3.7和Django 2.2。 - obadul024

Python3.8和Django2.2也有同样的问题。 - Drachenfels

Answer 1

进入 django 文件夹，然后进入此路径：

django\db\backends\mysql

然后前往operations.py文件并查找query = query.decode(errors='replace')语句。 删除此行并替换为query = errors='replace'

- Shahan Uddin

---

我确实使用了类似的东西，不过我不得不在 Django operations.py 文件中手动删除条件。我真的记不清是什么了，但它确实起作用了。 - obadul024

Answer 2

我认为你遇到了这个问题，是因为你正在使用PyMySQL。

这个问题在Django 3.0+中已经修复(ticket 30380)，但由于Django没有官方支持PyMySQL，所以没有被移植到Django 2.2.X中。

一些选项包括：

• 升级到Django 3.0.X+
• 从PyMySQL转换到mysqlclient
• 修补你的Django 2.2.X版本(参见此处的修复)

- Alasdair

Answer 3

我刚刚将Django版本从django==2.2切换到django==2.1，问题已经解决。

- Ombori

Answer 4

这是在旧版Django中出现的问题。

对我来说，v3.0.7解决了这个问题。

pip install django==3.0.7

- Om A.