Django Management Command argument obtained from execution of another program

Question

I need to run a Custom Django Management Command (module named populate_db.py) included in a management/commands directory. It populates a database.

restaurant/
    __init__.py
    models.py
    management/
        commands/
            _private.py
            populate_db.py
    tests.py
    views.py
    formDict.py

I want the command to take a mandatory argument as a dictionary. The mentioned dictionary can be obtained from the execution of another program named formDict.py

So I want a one-line command which will run formDict.py and consecutively take its result as an argument for my Custom Django Management Command python manage.py populate_db.

Is it possible to form such a command at all? If not, how to implement the idea alternatively?

You can run django background tasks take a look at my answer here: https://stackoverflow.com/questions/54225303/signal-django-to-run-a-task/54225921#54225921 and if you find it useful then don't forget to upvote it so that the community can take advantage of it. :) — Ahtisham, Feb 03 '19 at 22:53

score 1 · Answer 1 · answered Feb 04 '19 at 02:00

If fromDict.py prints to terminal (STDOUT), you can use a pipe (|) to get the parameter from STDIN in your management command, you can use sys.stdin for that. As you may want to execute the command by itself, it is a good idea to accept a string by parameter too.

Your management command would look line:

# populate_db.py
import argparse
import ast
import sys

from django.core.management.base import BaseCommand, CommandError


class Command(BaseCommand):
    help = 'Polulate the Database'

    def add_arguments(self, parser):
        parser.add_argument(
            'input_dict',
            nargs='?',
            type=str,
            default=None
        )

    def handle(self, *args, **options):
        if options['input_dict']:
            input_dict = options['input_dict']
        else:
            input_dict = sys.stdin.read()

        try:
            data = ast.literal_eval(input_dict)
        except SyntaxError:
            raise CommandError(f'Invalid dict input: {input_dict}')

        # populate the DB with data

You can execute that command with either:

Getting the dict from STDIN

python fromDict.py | python yourproject/manage.py populate_db

or

Passing the dict by parameter

python yourproject/manage.py populate_db '{'some': 'dict'}'

Note: Take care with literal_eval if the dict comes from an untrusted source, as someone could exploit it (with very large values, for exemple) to break the python interpreter.

I've done the code with python 3.7. If you are using python < 3.6, you need to replace the [f-string](https://www.python.org/dev/peps/pep-0498/) with `.format`. — Renan Ivo, Feb 04 '19 at 02:02
@aspiring The error you posted suggests your attribute is required. Did you added `nargs='?',` to `parser.add_argument` as the code in my answer does? Are you handling the absence of the parameter and getting it from stdin? If you can post the current code of `populate_db.py`, it might help. — Renan Ivo, Feb 04 '19 at 17:28

score 0 · Answer 2 · answered Feb 04 '19 at 00:51

Wrap the logic of formDict in a function. Call it inside the handle function of populate_db.py to access the result returned from form_dict.

or

move formDict.py to management/commands/ and use call_command inside formDict to call populate_db. https://docs.djangoproject.com/en/2.1/ref/django-admin/#running-management-commands-from-your-code.

Django Management Command argument obtained from execution of another program

2 Answers2