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"""
32. Callable defaults
You can pass callable objects as the ``default`` parameter to a field. When
the object is created without an explicit value passed in, Django will call
the method to determine the default value.
This example uses ``datetime.datetime.now`` as the default for the ``pub_date``
field.
"""
from django.db import models
from datetime import datetime
class Article(models.Model):
headline = models.CharField(max_length=100, default='Default headline')
pub_date = models.DateTimeField(default=datetime.now)
def __unicode__(self):
return self.headline
__test__ = {'API_TESTS':"""
>>> from datetime import datetime
# No articles are in the system yet.
>>> Article.objects.all()
[]
# Create an Article.
>>> a = Article(id=None)
# Grab the current datetime it should be very close to the default that just
# got saved as a.pub_date
>>> now = datetime.now()
# Save it into the database. You have to call save() explicitly.
>>> a.save()
# Now it has an ID. Note it's a long integer, as designated by the trailing "L".
>>> a.id
1L
# Access database columns via Python attributes.
>>> a.headline
u'Default headline'
# make sure the two dates are sufficiently close
>>> d = now - a.pub_date
>>> d.seconds < 5
True
# make sure that SafeString/SafeUnicode fields work
>>> from django.utils.safestring import SafeUnicode, SafeString
>>> a.headline = SafeUnicode(u'SafeUnicode Headline')
>>> a.save()
>>> a.headline = SafeString(u'SafeString Headline')
>>> a.save()
"""}
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