Is there a way to annotate django query with non-expression?

Question

I have use case where I need to get all objects where existing_field is the beginning of some string.

some string changes dynamically so I need a smart way to filter out objects.

My idea is to create annotated query like this:

MyModel.objects.annotate(annotated_field='some string').filter(annotated_field__startswith=F('existing_field'))

Currently it is failing with: QuerySet.annotate() received non-expression(s): some string

Is there a way to annotate objects with string value?

Answer 1

For those who are still facing the problem with newer versions of Django will have to use ExpressionWrapper and probably F

from django.db.models import ExpressionWrapper, F
MyModel.objects.annotate(annotated_field=ExpressionWrapper(Value('some string', output_field=CharField()))).filter(annotated_field__startswith=F('existing_field'))