Django REST framework IntegerField max_length issue

Question

I am getting an "__init__() got an unexpected keyword argument 'max_length'" error for my model field of IntegerField with max_length. The stack trace is as follows:

Environment:


Request Method: GET
Request URL: http://localhost:8000/api/jmc/foundation/

Django Version: 1.7.1
Python Version: 2.7.8
Installed Applications:
('django.contrib.admin',
 'django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.messages',
 'django.contrib.staticfiles',
 'dajaxice',
 'dajax',
 'rest_framework',
 'core',
 'analytics',
 'api')
Installed Middleware:
('django.contrib.sessions.middleware.SessionMiddleware',
 'django.middleware.common.CommonMiddleware',
 'django.middleware.csrf.CsrfViewMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django.contrib.auth.middleware.SessionAuthenticationMiddleware',
 'django.contrib.messages.middleware.MessageMiddleware',
 'django.middleware.clickjacking.XFrameOptionsMiddleware')


Traceback:
File "/usr/local/lib/python2.7/dist-packages/django/core/handlers/base.py" in get_response
  111.                     response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/views/decorators/csrf.py" in wrapped_view
  57.         return view_func(*args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/views/generic/base.py" in view
  69.             return self.dispatch(request, *args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/rest_framework/views.py" in dispatch
  406.             response = self.handle_exception(exc)
File "/usr/local/lib/python2.7/dist-packages/rest_framework/views.py" in dispatch
  403.             response = handler(request, *args, **kwargs)
File "/home/dev/Documents/Program Codes/Python/Django/Hera/api/views.py" in get
  17.         return Response(serializer.data)
File "/usr/local/lib/python2.7/dist-packages/rest_framework/serializers.py" in data
  547.         ret = super(ListSerializer, self).data
File "/usr/local/lib/python2.7/dist-packages/rest_framework/serializers.py" in data
  174.                 self._data = self.to_representation(self.instance)
File "/usr/local/lib/python2.7/dist-packages/rest_framework/serializers.py" in to_representation
  500.             self.child.to_representation(item) for item in iterable
File "/usr/local/lib/python2.7/dist-packages/rest_framework/serializers.py" in to_representation
  382.         fields = [field for field in self.fields.values() if not field.write_only]
File "/usr/local/lib/python2.7/dist-packages/rest_framework/serializers.py" in fields
  245.             for key, value in self.get_fields().items():
File "/usr/local/lib/python2.7/dist-packages/rest_framework/serializers.py" in get_fields
  911.             ret[field_name] = field_cls(**kwargs)
File "/usr/local/lib/python2.7/dist-packages/rest_framework/fields.py" in __init__
  597.         super(IntegerField, self).__init__(**kwargs)

Exception Type: TypeError at /api/jmc/foundation/
Exception Value: __init__() got an unexpected keyword argument 'max_length'

Community · Accepted Answer · 2018-01-02 00:36:37Z

3

You might want to use the MaxValueValidator with IntegerField instead of max_length.

from django.db import models
from django.core.validators import MaxValueValidator

class MyModel(models.Model):
    number = models.IntegerField(validators=[MaxValueValidator(100)])

edited Jan 2, 2018 at 0:36

CommunityBot

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answered Dec 23, 2014 at 7:39

Alasdair

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1 Comment

Kevin Brown-Silva Over a year ago

While this is technically correct, the error is being triggered by a Django REST Framework field and not a Django field. This answer doesn't actually answer the question, which was why the error was being triggered for DRF.

Sourabh Dev · Accepted Answer · 2014-12-23 07:14:05Z

1

Looks like IntegerField in Django doesn't have an max_length option. The reason we don't get any error is because Django suppresses it and 'Django REST framework' doesn't. Just removing the max_length option will make it work again.

answered Dec 23, 2014 at 7:14

Sourabh Dev

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1 Comment

Kevin Brown-Silva Over a year ago

All Django fields support the max_length option, just only a few need it. This is actually a known issue in DRF.

Kevin Brown-Silva · Accepted Answer · 2014-12-23 19:10:12Z

1

Contrary to popular belief and common sense, Django does support the max_length argument on the IntegerField as well as any other field. The error you are seeing here is a known issue with Django REST Framework that does not currently have a fix.

The easiest way to fix this in your serializers (until a fix is done in DRF) is to redefine the field on the serializer without the max_length argument.

class MySerializer(serializers.ModelSerializer):
    int_field = serializers.IntegerField()

answered Dec 23, 2014 at 19:10

Kevin Brown-Silva

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