Doc's data migration command not working

Using Django
#1

Hello,

I’ve been meaning to use the Django’s data migration feature, and the example command ( url ) :

python manage.py makemigrations --empty yourappname

I’ve replaced the yourappname with the correct app name I have registered, but then this error is raised :

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 "/home/benja/Documents/GitHub/tn_web/venv/lib/python3.8/site-packages/django/core/management/__init__.py", line 446, in execute_from_command_line
    utility.execute()
  File "/home/benja/Documents/GitHub/tn_web/venv/lib/python3.8/site-packages/django/core/management/__init__.py", line 440, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/home/benja/Documents/GitHub/tn_web/venv/lib/python3.8/site-packages/django/core/management/base.py", line 414, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/home/benja/Documents/GitHub/tn_web/venv/lib/python3.8/site-packages/django/core/management/base.py", line 460, in execute
    output = self.handle(*args, **options)
  File "/home/benja/Documents/GitHub/tn_web/venv/lib/python3.8/site-packages/django/core/management/base.py", line 98, in wrapped
    res = handle_func(*args, **kwargs)
  File "/home/benja/Documents/GitHub/tn_web/venv/lib/python3.8/site-packages/django/core/management/commands/makemigrations.py", line 181, in handle
    changes = {app: [Migration("custom", app)] for app in app_labels}
  File "/home/benja/Documents/GitHub/tn_web/venv/lib/python3.8/site-packages/django/core/management/commands/makemigrations.py", line 181, in <dictcomp>
    changes = {app: [Migration("custom", app)] for app in app_labels}
  File "/home/benja/Documents/GitHub/tn_web/venv/lib/python3.8/site-packages/django/db/migrations/migration.py", line 57, in __init__
    self.operations = list(self.__class__.operations)
AttributeError: type object 'Migration' has no attribute 'operations'

It seems to be a bug ? Did I do something wrong here ?

#2

Which version of Django are you using? Is it the latest patch version for the feature version (e.g. 4.0.7 for 4.0)?

#3

Hmm the line of code that’s crashing hasn’t changed in 9 years:

Try re-installing Django - perhaps something has modified your copy of Django. Another possibility is that some package you’ve installed is modifying the class in a weird way.

1 Like
#4

I was using 4.0.4 on my venv, installing 4.0.7 might have fixed it !

No idea what happened, but your solution was spot on, thank you and keep up with the good work !

#5

In future you could just delete the db.sqlite3 file and delete older migrations from the migration folder. Then the flush command (python manage.py flush), the db.sqlite3 file will generate itself again - but that would only be if you were comfortable with resetting the database completely

#6

I didn’t mean to erase all my data, the point of a data migration is to act on existing data :slight_smile:
Also, I’m not using db.sqlite3, but postgres in production. This needs to hit prod as well. Erasing prod db isn’t the solution :slight_smile:

#7

Ok ignore what I said then. I didn’t know it was in production :+1: