Why doesn't the simplest script with celery beat work?

Question

Python

A simple script throws an error.

import os
from celery import Celery


# set the default Django settings module for the 'celery' program.
os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'rik_ahrefs.settings')

celery = Celery('rik_ahrefs', broker='pyamqp://[email protected]//', backend='rpc://celery_backend')

# Using a string here means the worker doesn't have to serialize
# the configuration object to child processes.
# - namespace='CELERY' means all celery-related configuration keys
#   should have a `CELERY_` prefix.
celery.config_from_object('django.conf:settings', namespace='CELERY')

# Load task modules from all registered Django app configs.
celery.autodiscover_tasks()

celery.conf.beat_schedule = {
    'scan_master_sheet': {
        'task': 'tasks.scan_master_sheet',
        'schedule': 15.0,
        #'args': ('X','Z')
    },
}


@celery.task()
def scan_master_sheet(self):
    print('A!')

Mistake

(venv) E:\Work\rik_ahrefs>celery -A tasks beat
celery beat v4.2.0 (windowlicker) is starting.
__    -    ... __   -        _
LocalTime -> 2018-07-14 18:13:08
Configuration ->
    . broker -> amqp://guest:**@localhost:5672//
    . loader -> celery.loaders.app.AppLoader
    . scheduler -> celery.beat.PersistentScheduler
    . db -> celerybeat-schedule
    . logfile -> [stderr]@%WARNING
    . maxinterval -> 5.00 minutes (300s)
[2018-07-14 18:13:08,307: ERROR/MainProcess] Message Error: Couldn't apply scheduled task scan_master_sheet: scan_master_sheet() missing 1 required positional argument: 'self'
['  File "C:\\Python36\\lib\\runpy.py", line 193, in _run_module_as_main\n    "__main__", mod_spec)\n', '  File "C:\\Python36\\lib\\runpy.py", line 85, in _run_code\n    exec(code, run_globals)\n', '  File "E:\\Work\\rik_ahrefs\\venv\\Scripts\\celery.exe\\__main__.py", line 9, in <module>\n    sys.exit(main())\n', '  File "e:\\work\\rik_ahrefs\\venv\\lib\\site-packages\\celery\\__main__.py", line 16, in main\n    _main()\n', '  File "e:\\work\\rik_ahrefs\\venv\\lib\\site-packages\\celery\\bin\\celery.py", line 322, in main\n    cmd.execute_from_commandline(argv)\n', '  File "e:\\work\\rik_ahrefs\\venv\\lib\\site-packages\\celery\\bin\\celery.py", line 496, in execute_from_commandline\n    super(CeleryCommand, self).execute_from_commandline(argv)))\n', '  File "e:\\work\\rik_ahrefs\\venv\\lib\\site-packages\\celery\\bin\\base.py", line 275, in execute_from_commandline\n    return self.handle_argv(self.prog_name, argv[1:])\n', '  File "e:\\work\\rik_ahrefs\\venv\\lib\\site-packages\\celery\\bin\\celery.py", line 488, in handle_argv\n    return self.execute(command, argv)\n', '  File "e:\\work\\rik_ahrefs\\venv\\lib\\site-packages\\celery\\bin\\celery.py", line 420, in execute\n    ).run_from_argv(self.prog_name, argv[1:], command=argv[0])\n', '  File "e:\\work\\rik_ahrefs\\venv\\lib\\site-packages\\celery\\bin\\base.py", line 279, in run_from_argv\n    sys.argv if argv is None else argv, command)\n', '  File "e:\\work\\rik_ahrefs\\venv\\lib\\site-packages\\celery\\bin\\base.py", line 363, in handle_argv\n    return self(*args, **options)\n', '  File "e:\\work\\rik_ahrefs\\venv\\lib\\site-packages\\celery\\bin\\base.py", line 238, in __call__\n    ret = self.run(*args, **kwargs)\n', '  File "e:\\work\\rik_ahrefs\\venv\\lib\\site-packages\\celery\\bin\\beat.py", line 109, in run\n    return beat().run()\n', '  File "e:\\work\\rik_ahrefs\\venv\\lib\\site-packages\\celery\\apps\\beat.py", line 81, in run\n    self.start_scheduler()\n', '  File "e:\\work\\rik_ahrefs\\venv\\lib\\site-packages\\celery\\apps\\beat.py", line 109, in start_scheduler\n    service.start()\n', '  File "e:\\work\\rik_ahrefs\\venv\\lib\\site-packages\\celery\\beat.py", line 588, in start\n    interval = self.scheduler.tick()\n', '  File "e:\\work\\rik_ahrefs\\venv\\lib\\site-packages\\celery\\beat.py", line 307, in tick\n    self.apply_entry(entry, producer=self.producer)\n', '  File "e:\\work\\rik_ahrefs\\venv\\lib\\site-packages\\celery\\beat.py", line 244, in apply_entry\n    exc, traceback.format_stack(), exc_info=True)\n']
Traceback (most recent call last):
  File "e:\work\rik_ahrefs\venv\lib\site-packages\celery\beat.py", line 350, in apply_async
    **entry.options)
  File "e:\work\rik_ahrefs\venv\lib\site-packages\celery\app\task.py", line 513, in apply_async
    check_arguments(*(args or ()), **(kwargs or {}))
TypeError: scan_master_sheet() missing 1 required positional argument: 'self'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "e:\work\rik_ahrefs\venv\lib\site-packages\celery\beat.py", line 241, in apply_entry
    result = self.apply_async(entry, producer=producer, advance=False)
  File "e:\work\rik_ahrefs\venv\lib\site-packages\celery\beat.py", line 358, in apply_async
    entry, exc=exc)), sys.exc_info()[2])
  File "e:\work\rik_ahrefs\venv\lib\site-packages\vine\five.py", line 178, in reraise
    raise value.with_traceback(tb)
  File "e:\work\rik_ahrefs\venv\lib\site-packages\celery\beat.py", line 350, in apply_async
    **entry.options)
  File "e:\work\rik_ahrefs\venv\lib\site-packages\celery\app\task.py", line 513, in apply_async
    check_arguments(*(args or ()), **(kwargs or {}))
celery.beat.SchedulingError: Couldn't apply scheduled task scan_master_sheet: scan_master_sheet() missing 1 required positional argument: 'self'

Answer 1

@celery.task(bind=True)
def scan_master_sheet(self):
    print('A!')

Answer 2

Why do you need self if the function is not in a class?
Put it in and it should work. Or, when calling the function, pass any argument. def scan_master_sheet(self):