django/tests/db_functions/math/test_ln.py

import math
from decimal import Decimal

from django.db.models import DecimalField
from django.db.models.functions import Ln
from django.test import TestCase
from django.test.utils import register_lookup

from ..models import DecimalModel, FloatModel, IntegerModel


class LnTests(TestCase):

    def test_null(self):
        IntegerModel.objects.create()
        obj = IntegerModel.objects.annotate(null_ln=Ln('normal')).first()
        self.assertIsNone(obj.null_ln)

    def test_decimal(self):
        DecimalModel.objects.create(n1=Decimal('12.9'), n2=Decimal('0.6'))
        obj = DecimalModel.objects.annotate(n1_ln=Ln('n1'), n2_ln=Ln('n2')).first()
        self.assertIsInstance(obj.n1_ln, Decimal)
        self.assertIsInstance(obj.n2_ln, Decimal)
        self.assertAlmostEqual(obj.n1_ln, Decimal(math.log(obj.n1)))
        self.assertAlmostEqual(obj.n2_ln, Decimal(math.log(obj.n2)))

    def test_float(self):
        FloatModel.objects.create(f1=27.5, f2=0.33)
        obj = FloatModel.objects.annotate(f1_ln=Ln('f1'), f2_ln=Ln('f2')).first()
        self.assertIsInstance(obj.f1_ln, float)
        self.assertIsInstance(obj.f2_ln, float)
        self.assertAlmostEqual(obj.f1_ln, math.log(obj.f1))
        self.assertAlmostEqual(obj.f2_ln, math.log(obj.f2))

    def test_integer(self):
        IntegerModel.objects.create(small=20, normal=15, big=1)
        obj = IntegerModel.objects.annotate(
            small_ln=Ln('small'),
            normal_ln=Ln('normal'),
            big_ln=Ln('big'),
        ).first()
        self.assertIsInstance(obj.small_ln, float)
        self.assertIsInstance(obj.normal_ln, float)
        self.assertIsInstance(obj.big_ln, float)
        self.assertAlmostEqual(obj.small_ln, math.log(obj.small))
        self.assertAlmostEqual(obj.normal_ln, math.log(obj.normal))
        self.assertAlmostEqual(obj.big_ln, math.log(obj.big))

    def test_transform(self):
        with register_lookup(DecimalField, Ln):
            DecimalModel.objects.create(n1=Decimal('12.0'), n2=Decimal('0'))
            DecimalModel.objects.create(n1=Decimal('1.0'), n2=Decimal('0'))
            obj = DecimalModel.objects.filter(n1__ln__gt=0).get()
            self.assertEqual(obj.n1, Decimal('12.0'))