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