How to see if a value or object is in a QuerySet field

Question

How would I see if a value is in a QuerySet?

For example, if I have the following model:

class UserProfile(models.Model):     user = models.ForeignKey(User, unique=True)     first_name = models.CharField(max_length=50) 

How would I find out if the first_name 'David' is contained in a QuerySet? A way to do the following:

ld = UserProfile.objects.filter(...).values('first_name')     >>> for object in ld:     ...     if object['first_name'] =='David':     ...             print True 

Or if a particular user object is instead? Something like 'David' in QuerySet['first_name'] ? Thank you.

Answer 1

Simplest way is to use the get method of the manager:

try:     foo = Foo.objects.get(foo_name='David') except Foo.DoesNotExist:     print 'Nope' except Foo.MultipleObjectsReturned:     print 'Filter is a better choice here' 

The exists method is applicable also, if you don't need to get the object:

if Foo.objects.filter(foo_color='green').exists():     print 'Nice' 

If you already have the object and want to determine if it is contained in a queryset:

foo = Foo.objects.get(foo_name='David') qs = Foo.objects.filter(<criteria>) if foo in qs:     print 'Nice again' 

If you want to use a value instead of an object:

value = 'David' qs = Foo.objects.filter(<criteria>).values_list('foo_name',flat=True) if value in qs:     print 'Nice'