django 2 中的迁移错误； AttributeError：“str”对象没有属性“decode”

Posted 2023-03-23

【中文标题】django 2 中的迁移错误； AttributeError：“str”对象没有属性“decode”

【英文标题】：Migrations error in django 2; AttributeError: 'str' object has no attribute 'decode'

【发布时间】：2019-11-11 05:42:52

【问题描述】：

我正在我新建的名为“core”的应用程序上运行迁移。 当我在它上面运行迁移时，我收到一个错误，告诉我这个；

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

我在下面发布 Traceback；

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'

这是模型文件；

    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)

这是我正在使用的数据库（MySQL）的设置：

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

【问题讨论】：

它看起来像 Python2 的代码，可以使用 str.decode()

但我使用的是 Python 3.7 和 Django 2.2

是的，python3.8 和 django2.2 也有同样的问题

【参考方案1】：

转到 django 文件夹，然后转到此路径：

django\db\backends\mysql

然后转到operations.py 并找到query = query.decode(errors='replace')。 删除该行并放入query = errors='replace'

【讨论】：

我确实使用了类似的东西，我不得不手动删除 Django operations.py 文件中的条件。不记得它是什么，但它确实有效。

【参考方案2】：

我认为您遇到这个问题是因为您使用的是 PyMySQL。

该问题在 Django 3.0+ (ticket 30380) 中已修复，但在 Django 2.2.X 中已修复 wasn't backported，因为 Django 不正式支持 PyMySQL。

一些选项是：

升级到 Django 3.0.X+ 从 PyMySQL 切换到 mysqlclient 修补您的 Django 2.2.X 版本（请参阅修复程序 here）

【参考方案3】：

这是在较旧的 django 版本中出现的问题。

v3.0.7 为我解决了问题。

pip install django==3.0.7

【参考方案4】：

我刚刚将我的 django 版本从 django==2.2 切换到 django==2.1 并解决了