Processing command arguments in django

Question

I am trying to add some arguments to my django command. My command will be executing a sql query and I'd like to have an optional argument --first_row and if --first_row is specified the user must specify a second argment --last_row.

Here is what I have tried:

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

class Command(BaseCommand):
    def add_arguments(self, parser):
        parser.add_argument('--first_row', type=int)
        parser.add_argument('--last_row', type=int)

    def handle(self, *args, **options):
        import argparse
        parser = argparse.ArgumentParser()
        self.add_arguments(parser)

        start = time.time()
        args = parser.parse_args()
        if args.first_row:
            print "first row is %d" % (args.first_row)
        end = time.time()
        self.stdout.write(self.style.SUCCESS("Operation took %d seconds" % (end-start)))

But when I run my command I get this output:

manage.py > query_db --first_row 1 --last_row 5
usage: manage.py [-h] [--first_row FIRST_ROW] [--last_row LAST_ROW]
manage.py: error: unrecognized arguments: query_db

Process finished with exit code 2

What am I doing wrong?

What is the path to your command? Like Writing custom django-admin commands example ? — dani herrera
– dani herrera, Commented Mar 30, 2018 at 18:21

Alasdair · Accepted Answer · 2018-03-30 18:57:29Z

2

You shouldn't instantiate a new ArgumentParser in your handle method. It doesn't know about the query_db argument, so you get the unrecognized arguments: query_db error.

There are some suggestions of how to handle mutually inclusive arguments on this question. You could use the first suggestion and raise an error if first_row is present in options but last_row isn't:

from django.core.management import CommandError

def add_arguments(self, parser):
    parser.add_argument('--first_row', type=int)
    parser.add_argument('--last_row', type=int)

def handle(self, *args, **options):
    if options['first_row'] is not None and options['last_row'] is None:
        raise CommandError("--last_row is required when --first_row is specified)
    ...

edited Mar 30, 2018 at 18:57

answered Mar 30, 2018 at 18:47

Alasdair

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1 Comment

Alasdair Over a year ago

You could look at this question about only allowing positive integers with argparse. It might be simpler to add another if-statement in the handle method. There might be other checks you need to add, e.g. first_row <= last_row.

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