[Django 2.0 management command] Export all data related to the given user.

userdata.py

"""
Export all data related to the given user.
"""

from django.contrib.auth.models import User
from django.core.serializers import serialize
from django.core.management.base import BaseCommand, CommandError


class Command(BaseCommand):
    
    help = 'Export all data related to the given user'

    def serialize_model(self, instance):
        return serialize('yaml', [instance], indent=2,
                         use_natural_foreign_keys=True,
                         use_natural_primary_keys=True)

    def add_arguments(self, parser):
        parser.add_argument('user_id', help='Target user ID', type=int)

    def handle(self, *args, **options):
        user_id = options['user_id']

        fields = User._meta.get_fields(include_hidden=True)
        related_fields = filter(lambda f: f.is_relation, fields)
        
        try:
            user = User.objects.get(pk=user_id)
        except User.DoesNotExist:
            raise CommandError('No user found with ID={}'.format(user_id))

        output = []
        output.append(self.serialize_model(user))
        for relation in related_fields:
            model = relation.related_model
            instances = model.objects.filter(**{relation.remote_field.name: user_id})
            for instance in instances:
                output.append(self.serialize_model(instance))

        self.stdout.write("---\n")                 
        self.stdout.write('\n\n'.join(output))