Django Filters - or?

问题:

How would I do an \"or\" in a django filter.

Basically, I want to be able to list the items that either a user has added (they are listed as the creator) or the item has been approved

so I basically need to select

item.creator = owner or item.moderated = False

How would I do this in django (preferably with a filter/queryset)

回答1:

There is Q objects that allow to complex lookups. Example:

from django.db.models import Q

Item.objects.filter(Q(creator=owner) | Q(moderated=False))

回答2:

You can use the | operator to combine querysets directly without needing Q objects:

result = Item.objects.filter(item.creator = owner) | Item.objects.filter(item.moderated = False)

(edit - I was initially unsure if this caused an extra query but @spookylukey pointed out that lazy queryset evaluation takes care of that)

回答3:

You want to make filter dynamic then you have to use Lambda like

from django.db.models import Q

brands = [\'ABC\',\'DEF\' , \'GHI\']

queryset = Product.objects.filter(reduce(lambda x, y: x | y, [Q(brand=item) for item in brands]))

reduce(lambda x, y: x | y, [Q(brand=item) for item in brands]) is equivalent to

Q(brand=brands[0]) | Q(brand=brands[1]) | Q(brand=brands[2]) | .....

回答4:

It is worth to note that it\'s possible to add Q expressions.

For example:

from django.db.models import Q

query = Q(first_name=\'mark\')
query.add(Q(email=\'[e-mail]\'), Q.OR)
query.add(Q(last_name=\'doe\'), Q.AND)

queryset = User.objects.filter(query)

This ends up with a query like :

(first_name = \'mark\' or email = \'[e-mail]\') and last_name = \'doe\'

This way there is no need to deal with or operators, reduce\'s etc.

回答5:

Similar to older answera, but a bit simpler, without the lambda:

filter_kwargs = {
    \'field_a\': 123,
    \'field_b__in\': (3, 4, 5, ),
}

To filter these two conditions using OR:

Item.objects.filter(Q(field_a=123) | Q(field_b__in=(3, 4, 5, ))

To get the same result programmatically:

list_of_Q = [Q(**{key: val}) for key, val in filter_kwargs.items()]
Item.objects.filter(reduce(operator.or_, list_of_Q))

(broken in two lines here, for clarity)

operator is in standard library: import operator
From docstring:

or_(a, b) -- Same as a | b.

For Python3, reduce is not in standard library: from functools import reduce

---

P.S.

Don\'t forget to make sure list_of_Q is not empty - reduce() will choke on empty list, it needs at least one element.

回答6:

This might be useful https://docs.djangoproject.com/en/dev/topics/db/queries/#spanning-multi-valued-relationships

Basically it sounds like they act as OR