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from django.db.models import Value as V
from django.db.models.functions import Lower, StrIndex, Substr, Upper
from django.test import TestCase
from ..models import Author
class SubstrTests(TestCase):
def test_basic(self):
Author.objects.create(name='John Smith', alias='smithj')
Author.objects.create(name='Rhonda')
authors = Author.objects.annotate(name_part=Substr('name', 5, 3))
self.assertQuerysetEqual(
authors.order_by('name'), [' Sm', 'da'],
lambda a: a.name_part
)
authors = Author.objects.annotate(name_part=Substr('name', 2))
self.assertQuerysetEqual(
authors.order_by('name'), ['ohn Smith', 'honda'],
lambda a: a.name_part
)
# If alias is null, set to first 5 lower characters of the name.
Author.objects.filter(alias__isnull=True).update(
alias=Lower(Substr('name', 1, 5)),
)
self.assertQuerysetEqual(
authors.order_by('name'), ['smithj', 'rhond'],
lambda a: a.alias
)
def test_start(self):
Author.objects.create(name='John Smith', alias='smithj')
a = Author.objects.annotate(
name_part_1=Substr('name', 1),
name_part_2=Substr('name', 2),
).get(alias='smithj')
self.assertEqual(a.name_part_1[1:], a.name_part_2)
def test_pos_gt_zero(self):
with self.assertRaisesMessage(ValueError, "'pos' must be greater than 0"):
Author.objects.annotate(raises=Substr('name', 0))
def test_expressions(self):
Author.objects.create(name='John Smith', alias='smithj')
Author.objects.create(name='Rhonda')
substr = Substr(Upper('name'), StrIndex('name', V('h')), 5)
authors = Author.objects.annotate(name_part=substr)
self.assertQuerysetEqual(
authors.order_by('name'), ['HN SM', 'HONDA'],
lambda a: a.name_part
)
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