How do I do a not equal in Django queryset filtering?

the field=value syntax in queries is a shorthand for field__exact=value. That is to say that Django puts query operators on query fields in the identifiers. Django supports the following operators:

exact
iexact
contains
icontains
in
gt
gte
lt
lte
startswith
istartswith
endswith
iendswith
range

date
year
iso_year
month
day
week
week_day
iso_week_day
quarter
time
hour
minute
second

isnull
regex
iregex

I'm sure by combining these with the Q objects as Dave Vogt suggests and using filter() or exclude() as Jason Baker suggests you'll get exactly what you need for just about any possible query.

There are three options:

1. Chain exclude and filter

   results = Model.objects.exclude(a=True).filter(x=5)
   

2. Use Q() objects and the ~ operator

   from django.db.models import Q
   object_list = QuerySet.filter(~Q(a=True), x=5)
   

3. Register a custom lookup function

   from django.db.models import Lookup
   from django.db.models import Field
   
   @Field.register_lookup
   class NotEqual(Lookup):
       lookup_name = 'ne'
   
       def as_sql(self, compiler, connection):
           lhs, lhs_params = self.process_lhs(compiler, connection)
           rhs, rhs_params = self.process_rhs(compiler, connection)
           params = lhs_params + rhs_params
           return '%s <> %s' % (lhs, rhs), params
   

   Which can the be used as usual:

   results = Model.objects.exclude(a=True, x__ne=5)
   

You can use Q objects for this. They can be negated with the ~ operator and combined much like normal Python expressions:

from myapp.models import Entry
from django.db.models import Q

Entry.objects.filter(~Q(id=3))

will return all entries except the one(s) with 3 as their ID:

[<Entry: Entry object>, <Entry: Entry object>, <Entry: Entry object>, ...]

Your query appears to have a double negative, you want to exclude all rows where x is not 5, so in other words you want to include all rows where x is 5. I believe this will do the trick:

results = Model.objects.filter(x=5).exclude(a=True)

To answer your specific question, there is no "not equal to" field lookup but that's probably because Django has both filter and exclude methods available so you can always just switch the logic around to get the desired result.