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85ebb91846
model/field instance creation. Based on a patch from Richard Davies. git-svn-id: http://code.djangoproject.com/svn/django/trunk@8884 bcc190cf-cafb-0310-a4f2-bffc1f526a37
84 lines
2.5 KiB
Python
84 lines
2.5 KiB
Python
"""
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33. get_or_create()
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``get_or_create()`` does what it says: it tries to look up an object with the
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given parameters. If an object isn't found, it creates one with the given
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parameters.
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"""
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from django.db import models, IntegrityError
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class Person(models.Model):
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first_name = models.CharField(max_length=100)
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last_name = models.CharField(max_length=100)
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birthday = models.DateField()
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def __unicode__(self):
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return u'%s %s' % (self.first_name, self.last_name)
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class ManualPrimaryKeyTest(models.Model):
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id = models.IntegerField(primary_key=True)
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data = models.CharField(max_length=100)
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__test__ = {'API_TESTS':"""
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# Acting as a divine being, create an Person.
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>>> from datetime import date
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>>> p = Person(first_name='John', last_name='Lennon', birthday=date(1940, 10, 9))
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>>> p.save()
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# Only one Person is in the database at this point.
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>>> Person.objects.count()
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1
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# get_or_create() a person with similar first names.
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>>> p, created = Person.objects.get_or_create(first_name='John', last_name='Lennon', defaults={'birthday': date(1940, 10, 9)})
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# get_or_create() didn't have to create an object.
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>>> created
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False
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# There's still only one Person in the database.
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>>> Person.objects.count()
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1
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# get_or_create() a Person with a different name.
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>>> p, created = Person.objects.get_or_create(first_name='George', last_name='Harrison', defaults={'birthday': date(1943, 2, 25)})
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>>> created
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True
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>>> Person.objects.count()
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2
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# If we execute the exact same statement, it won't create a Person.
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>>> p, created = Person.objects.get_or_create(first_name='George', last_name='Harrison', defaults={'birthday': date(1943, 2, 25)})
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>>> created
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False
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>>> Person.objects.count()
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2
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# If you don't specify a value or default value for all required fields, you
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# will get an error.
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>>> try:
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... p, created = Person.objects.get_or_create(first_name='Tom', last_name='Smith')
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... except Exception, e:
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... if isinstance(e, IntegrityError):
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... print "Pass"
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... else:
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... print "Fail with %s" % type(e)
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Pass
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# If you specify an existing primary key, but different other fields, then you
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# will get an error and data will not be updated.
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>>> m = ManualPrimaryKeyTest(id=1, data='Original')
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>>> m.save()
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>>> try:
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... m, created = ManualPrimaryKeyTest.objects.get_or_create(id=1, data='Different')
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... except Exception, e:
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... if isinstance(e, IntegrityError):
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... print "Pass"
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... else:
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... print "Fail with %s" % type(e)
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Pass
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>>> ManualPrimaryKeyTest.objects.get(id=1).data == 'Original'
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True
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"""}
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