How do I set the value of a model object's property after using `get_field()`?

[Tom Tanner]

I'm making a terminal command for my Django app:

    from django.core.management.base import BaseCommand, CommandError
    from django.core.exceptions import FieldDoesNotExist
    from django.apps import apps
   
   
    class Command(BaseCommand):
        def add_arguments(self, parser):
            parser.add_argument(
                "--app",
                dest="app",
                required=True,
            )
   
            parser.add_argument(
                "--model",
                dest="model",
                required=True,
            )
   
            parser.add_argument(
                "--col",
                dest="col",
                required=True,
            )
   
        def handle(self, *args, **options):
            app_label = options.get('app')
            model_name = options.get('model')
            column_name = options.get('col')
   
            try:
                model = apps.get_model(app_label=app_label, model_name=model_name)
            except LookupError as e:
                msg = 'The model "%s" under the app "%s" does not exist!' \
                      % (model_name, app_label)
                raise CommandError(msg)
            try:
                column = model._meta.get_field(column_name)
            except FieldDoesNotExist as e:
                msg = 'The column "%s" does not match!' % column_name
                raise CommandError(msg)
            else:
                print(column, type(column))
                # Do stuff here with the column, model.

Right now, `column` is `<django.db.models.fields.IntegerField: column_name>`. I want this instance of `model` to have `column_name` set to `100`. How can I set and save this instance in this manner?

[Andrew Standley]

Hey Tom,
    First you'll need to create or get a particular instance of your model using one of it's managers  `model.objects` and a query. Ex for a model with a unique 'name' charfield: `model_obj = model.objects.get(name='MyObject')`
You can then use the column_name to set that attribute on the instance `setattr(model_obj, column_name) = 100` and finally save those changes `model_obj.save()`
See https://docs.djangoproject.com/en/1.11/topics/db/queries/#

-Andrew

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Linear Systems
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[Tom Tanner]

Darn, is this possible with a new object of the model? My idea is to in the end let the user input information that will be made into a new record to add to the model. But I need the user to type in the model they want to use...

[Dylan Reinhold]

Andrew,

   You do not to get the field with _meta.get_field just use setattr which takes a string as the field name.

Now if you are creating a new instance of your model and are just passing a single field all other fields would need to have defaults or be null=True.

In your do stuff area you can just run this to create a new object with the string 'Test Text':

    model_instance = model()
    setattr(model_instance, column_name, 'Test Text')
    model_instance.save()

 

Dylan

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