Migrations error in django 2; AttributeError: 'str' object has no attribute 'decode'

Question

I am running migrations on my newly built app called 'core'. When I run migrations on it, I get an error that tells me this;

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'

Here is the Models file;

    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)

Here is the Settings for the database I am using (MySQL) :

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

Hearse

it looks like code for Python2 which could use str.decode() – Remnant

but I am using Python 3.7 and Django 2.2 – Hearse

Yup same issue with python3.8 and django2.2 – Wash

Answer 1

Go to django folder, then go to this path:

django\db\backends\mysql

then go to operations.py and find query = query.decode(errors='replace'). Remove the line and put query = errors='replace'

Nette

I did actually use something similar, I had to manually remove the conditions in the Django operations.py file. Don't really remember what it was but it did work. – Hearse

Answer 2

I think you're hitting this issue because you're using PyMySQL.

The issue is fixed in Django 3.0+ (ticket 30380), but wasn't backported to Django 2.2.X because Django doesn't officially support PyMySQL.

Some options are:

• Upgrade to Django 3.0.X+
• Switch from PyMySQL to mysqlclient
• patch your version of Django 2.2.X (see the fix here)

Safe

this should be the accepted answer, thank you Alasdair! – Gretel

Answer 3

This is an issue that arises in older django versions.

v3.0.7 did the trick for me.

pip install django==3.0.7

Acuity

Answer 4

I just switched my django version from django==2.2 to django==2.1 and it was solved

Oscillatory