In Django model QuerySets, I see that there is a __gt and __lt for comparative values, but is there a __ne or != (not equals)? I want to filter out using a not equals. For example, for
Model:
bool a;
int x;
I want to do
results = Model.objects.exclude(a=True, x!=5)
The != is not correct syntax. I also tried __ne.
I ended up using:
results = Model.objects.exclude(a=True, x__lt=5).exclude(a=True, x__gt=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>, ...]
Entry.objects.filter(~Q(id=3)) rather than Entry.objects.exclude(id=3)? –
Nigh ~Q query with other ones as well. docs.djangoproject.com/en/3.2/topics/db/queries/… –
Carmancarmarthen Entry.objects.filter(~Q(param="good")).exists() –
Modiste 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.
results = Model.objects.filter(a=true).exclude(x=5) –
Boatbill objects.exclude(**filter1).filter(**filter2) gives different results from objects.filter(**filter1).exclude(**filter2), while ~Q will always get correct negation inside objects.filter(**filter_with_Q) –
Acidimeter exclude and filter calls didn't make any meaningful difference. The order of the conditions in the WHERE clause changes, but how does that matter? –
Breathed 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.
tg=Tag.objects.filter(user=request.user).exclude(name__regex=r'^(public|url)$') and it works. –
Virulent icontains, iexact and similar stands for "ignore case sensitivity". It is not for "inverse". –
Unsnap exclude() with multiple terms, you may want to compose the proposition with the OR operator, e.g. exclude(Q(field1__queryop1=value1) | Q(field2__queryop2=value2)) in order to exclude the results under both conditions. –
Fullmouthed There are three options:
results = Model.objects.exclude(a=True).filter(x=5)
Use Q() objects and the ~ operator
from django.db.models import Q
object_list = QuerySet.filter(~Q(a=True), x=5)
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)
exclude will add something to the WHERE clause, so it can be pretty efficient. See docs.djangoproject.com/en/3.2/ref/models/querysets/#exclude. @Longlived –
Antipyrine It's easy to create a custom lookup, there's an __ne lookup example in Django's 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, 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
Then you need to register it:
from django.db.models 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)
While you can filter Models with =, __gt, __gte, __lt, __lte, you cannot use ne or !=. However, you can achieve better filtering using the Q object.
You can avoid chaining QuerySet.filter() and QuerySet.exclude(), and use this:
from django.db.models import Q
object_list = QuerySet.filter(~Q(field='not wanted'), field='wanted')
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...)
Using exclude and filter
results = Model.objects.filter(x=5).exclude(a=true)
You should use filter and exclude like this
results = Model.objects.exclude(a=true).filter(x=5)
This will give your desired result.
from django.db.models import Q
results = Model.objects.exclude(Q(a=True) & ~Q(x=5))
for not equal you can use ~ on an equal query. obviously, Q can be used to reach the equal query.
Q(a=True) and ~Q(x=5) would evaluate to ~Q(x=5) as arguments to .exclude. Please read: docs.python.org/3/reference/expressions.html#boolean-operations and docs.python.org/3/reference/… . –
Dodgem 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)
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)
This should work
results = Model.objects.filter(x=5).exclude(a=True)
results = Model.objects.filter(a = True).exclude(x = 5)Generetes this sql:
select * from tablex where a != 0 and x !=5The sql depends on how your True/False field is represented, and the database engine. The django code is all you need though.
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.
results = Model.objects.filter(a__in=[False,None],x=5) –
Bicameral Watch out for lots of incorrect answers to this question!
Gerard's logic is correct, though it will return a list rather than a queryset (which might not matter).
If you need a queryset, use Q:
from django.db.models import Q
results = Model.objects.filter(Q(a=false) | Q(x=5))
If we need to exclude/negate based on the sub queryset we can use,
When a conditional expression returns a boolean value, it is possible to use it directly in filters. Here non_unique_account_type returns a boolean value. But, still, we can use it in the filter.
>>> non_unique_account_type = Client.objects.filter(
... account_type=OuterRef('account_type'),
... ).exclude(pk=OuterRef('pk')).values('pk')
>>> Client.objects.filter(~Exists(non_unique_account_type))
In the SQL terms, it evaluates to:
SELECT * FROM client c0
WHERE NOT EXISTS (
SELECT c1.id
FROM client c1
WHERE c1.account_type = c0.account_type AND NOT c1.id = c0.id
)
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a=truefirst and then applies thex=5filter on the remaining. The intended query required only those witha=trueandx!=5. The difference being that all those witha=trueandx=5are also filtered out. – Unweave