问题
I'm using Django 2.0, Python 3.7, and MySql 5. I have the following two models, the second dependent on the first ...
class CoopType(models.Model):
name = models.CharField(max_length=200, null=False)
class Meta:
unique_together = ("name",)
class Coop(models.Model):
name = models.CharField(max_length=250, null=False)
type = models.ForeignKey(CoopType, on_delete=None)
address = AddressField(on_delete=models.CASCADE)
enabled = models.BooleanField(default=True, null=False)
phone = PhoneNumberField(null=True)
email = models.EmailField(null=True)
web_site = models.TextField()
I'm creating some seed data for the second model. I was wondering if there was a way to auto-generate data for the first model from within the second model. I tried this ...
- model: maps.coop
pk: 1
fields:
name: "1871"
type:
pk: null
name: Coworking Space
address:
street_number: 222
route: 1212
raw: 222 W. Merchandise Mart Plaza, Suite 1212
formatted: 222 W. Merchandise Mart Plaza, Suite 1212
locality:
name: Chicago
postal_code: 60654
state:
code: IL
enabled: True
phone:
email:
web_site: "http://www.1871.com/"
latitude: 41.88802611
longitude: -87.63612199
but I get this error when running the seed data ...
(env) localhost:maps davea$ python scripts/parse_coop_csv.py ~/Downloads/chicommons_prep.xlsx\ -\ Mapping\ Sheet.csv > maps/fixtures/seed_data.yaml
(env) localhost:maps davea$ python manage.py loaddata maps/fixtures/seed_data.yaml
Traceback (most recent call last):
File "/Users/davea/Documents/workspace/chicommons/maps/env/lib/python3.7/site-packages/django/db/models/fields/__init__.py", line 923, in to_python
return int(value)
TypeError: int() argument must be a string, a bytes-like object or a number, not 'dict'
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "/Users/davea/Documents/workspace/chicommons/maps/env/lib/python3.7/site-packages/django/core/serializers/python.py", line 157, in Deserializer
data[field.attname] = model._meta.get_field(field_name).to_python(field_value)
File "/Users/davea/Documents/workspace/chicommons/maps/env/lib/python3.7/site-packages/django/db/models/fields/__init__.py", line 928, in to_python
params={'value': value},
django.core.exceptions.ValidationError: ["'{'pk': None, 'name': 'Coworking Space'}' value must be an integer."]
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "manage.py", line 21, in <module>
main()
File "manage.py", line 17, in main
execute_from_command_line(sys.argv)
File "/Users/davea/Documents/workspace/chicommons/maps/env/lib/python3.7/site-packages/django/core/management/__init__.py", line 371, in execute_from_command_line
utility.execute()
File "/Users/davea/Documents/workspace/chicommons/maps/env/lib/python3.7/site-packages/django/core/management/__init__.py", line 365, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/Users/davea/Documents/workspace/chicommons/maps/env/lib/python3.7/site-packages/django/core/management/base.py", line 288, in run_from_argv
self.execute(*args, **cmd_options)
File "/Users/davea/Documents/workspace/chicommons/maps/env/lib/python3.7/site-packages/django/core/management/base.py", line 335, in execute
output = self.handle(*args, **options)
File "/Users/davea/Documents/workspace/chicommons/maps/env/lib/python3.7/site-packages/django/core/management/commands/loaddata.py", line 72, in handle
self.loaddata(fixture_labels)
File "/Users/davea/Documents/workspace/chicommons/maps/env/lib/python3.7/site-packages/django/core/management/commands/loaddata.py", line 113, in loaddata
self.load_label(fixture_label)
File "/Users/davea/Documents/workspace/chicommons/maps/env/lib/python3.7/site-packages/django/core/management/commands/loaddata.py", line 168, in load_label
for obj in objects:
File "/Users/davea/Documents/workspace/chicommons/maps/env/lib/python3.7/site-packages/django/core/serializers/pyyaml.py", line 73, in Deserializer
yield from PythonDeserializer(yaml.load(stream, Loader=SafeLoader), **options)
File "/Users/davea/Documents/workspace/chicommons/maps/env/lib/python3.7/site-packages/django/core/serializers/python.py", line 159, in Deserializer
raise base.DeserializationError.WithData(e, d['model'], d.get('pk'), field_value)
django.core.serializers.base.DeserializationError: Problem installing fixture '/Users/davea/Documents/workspace/chicommons/maps/maps/maps/fixtures/seed_data.yaml': ["'{'pk': None, 'name': 'Coworking Space'}' value must be an integer."]: (maps.coop:pk=1) field_value was '{'pk': None, 'name': 'Coworking Space'}'
Is there any way to do this elegantly in the seed_data.yaml file?
回答1:
Solution: Update your fixtures as per the following
- model: test_app.coop
pk: 1
fields:
name: '1871'
type:
- Coworking Space
enabled: true
email: null
web_site: ''
- model: test_app.coop
pk: 2
fields:
name: '18715'
type:
- Coworking Space 2
enabled: true
email: null
web_site: ''
- model: test_app.coop
pk: 3
fields:
name: '187156'
type:
- Coworking Space 3
enabled: true
email: null
web_site: ''
And add a custom manager in your CoopType model
class CoopManager(models.Manager):
def get_by_natural_key(self, name):
return self.get_or_create(name=name)[0]
class CoopType(models.Model):
name = models.CharField(max_length=200)
objects = CoopManager()
class Meta:
unique_together = ("name",)
Now when you load the fixtures it will create the CoopType objects if not already exists and then load Coop model
Explanation: This is the Django code responsible for deserializing the objects
# Handle FK fields
elif field.remote_field and isinstance(field.remote_field, models.ManyToOneRel):
model = field.remote_field.model
if field_value is not None:
try:
default_manager = model._default_manager
field_name = field.remote_field.field_name
if hasattr(default_manager, 'get_by_natural_key'):
if hasattr(field_value, '__iter__') and not isinstance(field_value, six.text_type):
obj = default_manager.db_manager(db).get_by_natural_key(*field_value)
value = getattr(obj, field.remote_field.field_name)
# If this is a natural foreign key to an object that
# has a FK/O2O as the foreign key, use the FK value
if model._meta.pk.remote_field:
value = value.pk
else:
value = model._meta.get_field(field_name).to_python(field_value)
data[field.attname] = value
else:
data[field.attname] = model._meta.get_field(field_name).to_python(field_value)
except Exception as e:
raise base.DeserializationError.WithData(e, d['model'], d.get('pk'), field_value)
else:
data[field.attname] = None
Source: django.core.serializers.python line 152 onwards
As you can see if get_by_natural_key function is given in model and fixtures has nested data then it calls get_by_natural_key function to get the object. So in get_by_natural_key function we can use get_or_create and return the instance.
Please check that nested data in the Coop model has only args and not the kwargs because Django code pass args in this function.
PS: I am not sure how correct it is to use get_or_create in get_by_natural_key function but This is the only working solution for now.
来源：https://stackoverflow.com/questions/59940160/is-there-a-way-in-a-seed-data-yaml-file-to-autogenerate-models-on-which-first-mo