How do I do a not equal in Django queryset filteri

问题:

In Django model QuerySets, I see that there is a __gt and __lt for comparitive values, but is there a __ne/!=/<> (not equals?)

I want to filter out using a not equals:

Example:

Model:
    bool a;
    int x;

I want

results = Model.objects.exclude(a=true, x!=5)

The != is not correct syntax. I tried __ne, <>.

I ended up using:

results = Model.objects.exclude(a=true, x__lt=5).exclude(a=true, x__gt=5)

回答1:

Maybe Q objects could be of help for this problem. I've never used them but it seems they can be negated and combined much like normal python expressions.

Update: I Just tried it out, it seems to work pretty well:

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

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

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

回答2:

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" but that's probably because django has both "filter" and "exclude" methods available so you can always just switch the logic round to get the desired result.

回答3:

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
year
month
day
week_day
isnull
search
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.

回答4:

It's easy to create a custom lookup with Django 1.7. There's an __ne lookup example in Django official documentation.

You need to create the lookup itself first:

from django.db.models import Lookup

class NotEqual(Lookup):
    lookup_name = 'ne'

    def as_sql(self, qn, connection):
        lhs, lhs_params = self.process_lhs(qn, connection)
        rhs, rhs_params = self.process_rhs(qn, connection)
        params = lhs_params + rhs_params
        return '%s <> %s' % (lhs, rhs), params

Then you need to register it:

from django.db.models.fields import Field
Field.register_lookup(NotEqual)

And now you can use the __ne lookup in your queries like this:

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

回答5:

In Django 1.9/1.10 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.fields 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
   

   The register_lookup decorator was added in Django 1.8 and enables custom lookup as usual:

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

回答6:

While with the Models, you can filter with =, __gt, __gte, __lt, __lte, you cannot use ne, != or <>. However, you can achieve better filtering on using the Q object.

You can avoid chaining QuerySet.filter() and QuerySet.exlude(), and use this:

from django.db.models import Q
object_list = QuerySet.filter(~Q(field='not wanted'), field='wanted')

回答7:

Pending design decision. Meanwhile, use exclude()

The Django issue tracker has the remarkable entry #5763, titled "Queryset doesn't have a "not equal" filter operator". It is remarkable because (as of April 2016) it was "opened 9 years ago" (in the Django stone age), "closed 4 years ago", and "last changed 5 months ago".

Read through the discussion, it is interesting. Basically, some people argue __ne should be added while others say exclude() is clearer and hence __ne should not be added.

(I agree with the former, because the latter argument is roughly equivalent to saying Python should not have != because it has == and not already...)

回答8:

You should use filter and exclude like this

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

回答9:

Using exclude and filter

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

回答10:

The last bit of code will exclude all objects where x!=5 and a is True. Try this:

results = Model.objects.filter(a=False, x=5)

Remember, the = sign in the above line is assigning False to the parameter a and the number 5 to the parameter x. It's not checking for equality. Thus, there isn't really any way to use the != symbol in a query call.

回答11:

What you are looking for are all objects that have either a=false or x=5. In Django, | serves as OR operator between querysets:

results = Model.objects.filter(a=false)|Model.objects.filter(x=5)

回答12:

Django-model-values (disclosure: author) provides an implementation of the NotEqual lookup, as in this answer. It also provides syntactic support for it:

from model_values import F
Model.objects.exclude(F.x != 5, a=True)

回答13:

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

Generetes this sql:

select * from tablex where a != 0 and x !=5

The sql depends on how your True/False field is represented, and the database engine. The django code is all you need though.