Django -- User.DoesNotExist does not exist?

Question

I'm trying to get hold of Django. I use Pydev on Eclipse. I have written a simple signup page that I can't get to work. Eclipse complains that User.DoesNotExist is undefined. Most likely, I am missing something trivial. Here's the relevant portion of the code:

from django.contrib.auth.models import User
...
class SignUpForm (forms.Form):
    ...
    def clean_username (self): 
        try:
            User.objects.get(username=self.cleaned_data['username'])
        except User.DoesNotExist:
            return self.cleaned_data['username']
        raise forms.ValidationError(USERNAME_ALREADY_IN_USE)
    ...

Answer 1

The problem is really with PyDev, not your code. What you have done is absolutely correct, but IDEs will always have difficulty resolving attributes in a dynamic language like Python. In the case of the DoesNotExist exception, it is added via a __metaclass__ rather than through normal object inheritance, so PyDev is unlikely to be able to find it. However, it should definitely work.

Answer 2

I just discovered Pydev actually has a nice workaround for this.

Go to Window > Preferences, then Pydev > Editor > Code Analysis.

Click the Undefined tab and add "DoesNotExist" to the text box titled Consider the following names as globals.

Answer 3

Pydev has a workaround for such cases (when the members are defined at runtime). Just add #@UndefinedVariable at the end of the string which cause the warning (or ctrl+1 on keyboard when the cursor is at "DoesNotExist"), and it won't complain.