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Asked: 2026-05-14T08:57:01+00:00

How can I test to see if a class contains a particular attribute? In

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How can I test to see if a class contains a particular attribute?

In [14]: user = User.objects.get(pk=2)  

In [18]: user.__dict__  
Out[18]:   
{'date_joined': datetime.datetime(2010, 3, 17, 15, 20, 45),  
 'email': u'IloveDick@nwo.gov',  
 'first_name': u'',  
 'id': 2L,  
 'is_active': 1,  
 'is_staff': 0,  
 'is_superuser': 0,  
 'last_login': datetime.datetime(2010, 3, 17, 16, 15, 35),  
 'last_name': u'',  
 'password': u'sha1$44a2055f5',  
 'username': u'DickCheney'}  

In [25]: hasattr(user, 'username')  
Out[25]: True  

In [26]: hasattr(User, 'username')  
Out[26]: False

I’m having a weird bug where more attributes are showing up than I actually define.
I want to conditionally stop this.

e.g.

if not hasattr(User, 'karma'):
  User.add_to_class('karma', models.PositiveIntegerField(default=1))
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1 Answer

  1. Editorial Team

    as far as I know there is no method like hasattr() for Django models. But there is a way to check if a Django model has a certain field.

    To test this I would recommend you to access the Django (Python) shell:

    $> python manage.py shell

    Now import the User model:

    $> from django.contrib.auth.models import User

    Get the meta information of the model:

    $> opts = User._meta

    To check a field use the following command:

    $> opts.get_field('username')

    In case of the User model there will be printed out a message like this:

    <django.db.models.fields.CharField object at 0x1024750>

    If the field you are looking for is not part of the model a FieldDoesNotExist will be thrown. With this knowledge you should be able to check the existence of a field programmatically.

    You can read more about that here: b-list.org: Working with models

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