359 lines
12 KiB
Python
359 lines
12 KiB
Python
"""
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1. Bare-bones model
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This is a basic model with only two non-primary-key fields.
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"""
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from django.db import models
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class Article(models.Model):
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headline = models.CharField(maxlength=100, default='Default headline')
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pub_date = models.DateTimeField()
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def __str__(self):
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return self.headline
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__test__ = {'API_TESTS': """
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# No articles are in the system yet.
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>>> Article.objects.all()
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[]
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# Create an Article.
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>>> from datetime import datetime
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>>> a = Article(id=None, headline='Area man programs in Python', pub_date=datetime(2005, 7, 28))
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# Save it into the database. You have to call save() explicitly.
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>>> a.save()
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# Now it has an ID. Note it's a long integer, as designated by the trailing "L".
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>>> a.id
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1L
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# Access database columns via Python attributes.
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>>> a.headline
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'Area man programs in Python'
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>>> a.pub_date
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datetime.datetime(2005, 7, 28, 0, 0)
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# Change values by changing the attributes, then calling save().
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>>> a.headline = 'Area woman programs in Python'
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>>> a.save()
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# Article.objects.all() returns all the articles in the database.
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>>> Article.objects.all()
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[<Article: Area woman programs in Python>]
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# Django provides a rich database lookup API.
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>>> Article.objects.get(id__exact=1)
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<Article: Area woman programs in Python>
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>>> Article.objects.get(headline__startswith='Area woman')
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<Article: Area woman programs in Python>
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>>> Article.objects.get(pub_date__year=2005)
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<Article: Area woman programs in Python>
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>>> Article.objects.get(pub_date__year=2005, pub_date__month=7)
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<Article: Area woman programs in Python>
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>>> Article.objects.get(pub_date__year=2005, pub_date__month=7, pub_date__day=28)
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<Article: Area woman programs in Python>
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# The "__exact" lookup type can be omitted, as a shortcut.
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>>> Article.objects.get(id=1)
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<Article: Area woman programs in Python>
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>>> Article.objects.get(headline='Area woman programs in Python')
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<Article: Area woman programs in Python>
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>>> Article.objects.filter(pub_date__year=2005)
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[<Article: Area woman programs in Python>]
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>>> Article.objects.filter(pub_date__year=2004)
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[]
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>>> Article.objects.filter(pub_date__year=2005, pub_date__month=7)
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[<Article: Area woman programs in Python>]
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# Django raises an Article.DoesNotExist exception for get() if the parameters
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# don't match any object.
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>>> Article.objects.get(id__exact=2)
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Traceback (most recent call last):
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...
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DoesNotExist: Article matching query does not exist.
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>>> Article.objects.get(pub_date__year=2005, pub_date__month=8)
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Traceback (most recent call last):
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...
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DoesNotExist: Article matching query does not exist.
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# Lookup by a primary key is the most common case, so Django provides a
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# shortcut for primary-key exact lookups.
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# The following is identical to articles.get(id=1).
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>>> Article.objects.get(pk=1)
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<Article: Area woman programs in Python>
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# pk can be used as a shortcut for the primary key name in any query
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>>> Article.objects.filter(pk__in=[1])
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[<Article: Area woman programs in Python>]
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# Model instances of the same type and same ID are considered equal.
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>>> a = Article.objects.get(pk=1)
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>>> b = Article.objects.get(pk=1)
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>>> a == b
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True
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# You can initialize a model instance using positional arguments, which should
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# match the field order as defined in the model.
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>>> a2 = Article(None, 'Second article', datetime(2005, 7, 29))
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>>> a2.save()
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>>> a2.id
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2L
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>>> a2.headline
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'Second article'
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>>> a2.pub_date
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datetime.datetime(2005, 7, 29, 0, 0)
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# ...or, you can use keyword arguments.
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>>> a3 = Article(id=None, headline='Third article', pub_date=datetime(2005, 7, 30))
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>>> a3.save()
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>>> a3.id
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3L
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>>> a3.headline
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'Third article'
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>>> a3.pub_date
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datetime.datetime(2005, 7, 30, 0, 0)
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# You can also mix and match position and keyword arguments, but be sure not to
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# duplicate field information.
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>>> a4 = Article(None, 'Fourth article', pub_date=datetime(2005, 7, 31))
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>>> a4.save()
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>>> a4.headline
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'Fourth article'
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# Don't use invalid keyword arguments.
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>>> a5 = Article(id=None, headline='Invalid', pub_date=datetime(2005, 7, 31), foo='bar')
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Traceback (most recent call last):
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...
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TypeError: 'foo' is an invalid keyword argument for this function
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# You can leave off the value for an AutoField when creating an object, because
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# it'll get filled in automatically when you save().
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>>> a5 = Article(headline='Article 6', pub_date=datetime(2005, 7, 31))
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>>> a5.save()
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>>> a5.id
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5L
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>>> a5.headline
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'Article 6'
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# If you leave off a field with "default" set, Django will use the default.
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>>> a6 = Article(pub_date=datetime(2005, 7, 31))
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>>> a6.save()
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>>> a6.headline
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'Default headline'
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# For DateTimeFields, Django saves as much precision (in seconds) as you
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# give it.
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>>> a7 = Article(headline='Article 7', pub_date=datetime(2005, 7, 31, 12, 30))
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>>> a7.save()
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>>> Article.objects.get(id__exact=7).pub_date
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datetime.datetime(2005, 7, 31, 12, 30)
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>>> a8 = Article(headline='Article 8', pub_date=datetime(2005, 7, 31, 12, 30, 45))
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>>> a8.save()
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>>> Article.objects.get(id__exact=8).pub_date
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datetime.datetime(2005, 7, 31, 12, 30, 45)
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>>> a8.id
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8L
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# Saving an object again doesn't create a new object -- it just saves the old one.
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>>> a8.save()
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>>> a8.id
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8L
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>>> a8.headline = 'Updated article 8'
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>>> a8.save()
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>>> a8.id
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8L
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>>> a7 == a8
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False
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>>> a8 == Article.objects.get(id__exact=8)
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True
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>>> a7 != a8
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True
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>>> Article.objects.get(id__exact=8) != Article.objects.get(id__exact=7)
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True
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>>> Article.objects.get(id__exact=8) == Article.objects.get(id__exact=7)
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False
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# dates() returns a list of available dates of the given scope for the given field.
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>>> Article.objects.dates('pub_date', 'year')
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[datetime.datetime(2005, 1, 1, 0, 0)]
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>>> Article.objects.dates('pub_date', 'month')
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[datetime.datetime(2005, 7, 1, 0, 0)]
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>>> Article.objects.dates('pub_date', 'day')
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[datetime.datetime(2005, 7, 28, 0, 0), datetime.datetime(2005, 7, 29, 0, 0), datetime.datetime(2005, 7, 30, 0, 0), datetime.datetime(2005, 7, 31, 0, 0)]
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>>> Article.objects.dates('pub_date', 'day', order='ASC')
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[datetime.datetime(2005, 7, 28, 0, 0), datetime.datetime(2005, 7, 29, 0, 0), datetime.datetime(2005, 7, 30, 0, 0), datetime.datetime(2005, 7, 31, 0, 0)]
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>>> Article.objects.dates('pub_date', 'day', order='DESC')
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[datetime.datetime(2005, 7, 31, 0, 0), datetime.datetime(2005, 7, 30, 0, 0), datetime.datetime(2005, 7, 29, 0, 0), datetime.datetime(2005, 7, 28, 0, 0)]
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# dates() requires valid arguments.
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>>> Article.objects.dates()
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Traceback (most recent call last):
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...
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TypeError: dates() takes at least 3 arguments (1 given)
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>>> Article.objects.dates('invalid_field', 'year')
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Traceback (most recent call last):
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...
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FieldDoesNotExist: Article has no field named 'invalid_field'
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>>> Article.objects.dates('pub_date', 'bad_kind')
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Traceback (most recent call last):
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...
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AssertionError: 'kind' must be one of 'year', 'month' or 'day'.
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>>> Article.objects.dates('pub_date', 'year', order='bad order')
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Traceback (most recent call last):
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...
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AssertionError: 'order' must be either 'ASC' or 'DESC'.
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# Use iterator() with dates() to return a generator that lazily requests each
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# result one at a time, to save memory.
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>>> for a in Article.objects.dates('pub_date', 'day', order='DESC').iterator():
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... print repr(a)
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datetime.datetime(2005, 7, 31, 0, 0)
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datetime.datetime(2005, 7, 30, 0, 0)
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datetime.datetime(2005, 7, 29, 0, 0)
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datetime.datetime(2005, 7, 28, 0, 0)
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# You can combine queries with & and |.
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>>> s1 = Article.objects.filter(id__exact=1)
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>>> s2 = Article.objects.filter(id__exact=2)
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>>> s1 | s2
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[<Article: Area woman programs in Python>, <Article: Second article>]
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>>> s1 & s2
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[]
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# You can get the number of objects like this:
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>>> len(Article.objects.filter(id__exact=1))
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1
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# You can get items using index and slice notation.
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>>> Article.objects.all()[0]
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<Article: Area woman programs in Python>
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>>> Article.objects.all()[1:3]
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[<Article: Second article>, <Article: Third article>]
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>>> s3 = Article.objects.filter(id__exact=3)
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>>> (s1 | s2 | s3)[::2]
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[<Article: Area woman programs in Python>, <Article: Third article>]
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# Slices (without step) are lazy:
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>>> Article.objects.all()[0:5].filter()
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[<Article: Area woman programs in Python>, <Article: Second article>, <Article: Third article>, <Article: Fourth article>, <Article: Article 6>]
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# Slicing again works:
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>>> Article.objects.all()[0:5][0:2]
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[<Article: Area woman programs in Python>, <Article: Second article>]
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>>> Article.objects.all()[0:5][:2]
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[<Article: Area woman programs in Python>, <Article: Second article>]
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>>> Article.objects.all()[0:5][4:]
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[<Article: Article 6>]
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>>> Article.objects.all()[0:5][5:]
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[]
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# Some more tests!
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>>> Article.objects.all()[2:][0:2]
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[<Article: Third article>, <Article: Fourth article>]
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>>> Article.objects.all()[2:][:2]
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[<Article: Third article>, <Article: Fourth article>]
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>>> Article.objects.all()[2:][2:3]
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[<Article: Article 6>]
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# Note that you can't use 'offset' without 'limit' (on some dbs), so this doesn't work:
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>>> Article.objects.all()[2:]
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Traceback (most recent call last):
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...
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AssertionError: 'offset' is not allowed without 'limit'
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# Also, once you have sliced you can't filter, re-order or combine
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>>> Article.objects.all()[0:5].filter(id=1)
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Traceback (most recent call last):
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...
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AssertionError: Cannot filter a query once a slice has been taken.
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>>> Article.objects.all()[0:5].order_by('id')
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Traceback (most recent call last):
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...
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AssertionError: Cannot reorder a query once a slice has been taken.
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>>> Article.objects.all()[0:1] & Article.objects.all()[4:5]
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Traceback (most recent call last):
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...
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AssertionError: Cannot combine queries once a slice has been taken.
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# Negative slices are not supported, due to database constraints.
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# (hint: inverting your ordering might do what you need).
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>>> Article.objects.all()[-1]
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Traceback (most recent call last):
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...
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AssertionError: Negative indexing is not supported.
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>>> Article.objects.all()[0:-5]
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Traceback (most recent call last):
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...
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AssertionError: Negative indexing is not supported.
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# An Article instance doesn't have access to the "objects" attribute.
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# That's only available on the class.
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>>> a7.objects.all()
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Traceback (most recent call last):
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...
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AttributeError: Manager isn't accessible via Article instances
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>>> a7.objects
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Traceback (most recent call last):
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...
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AttributeError: Manager isn't accessible via Article instances
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# Bulk delete test: How many objects before and after the delete?
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>>> Article.objects.all()
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[<Article: Area woman programs in Python>, <Article: Second article>, <Article: Third article>, <Article: Fourth article>, <Article: Article 6>, <Article: Default headline>, <Article: Article 7>, <Article: Updated article 8>]
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>>> Article.objects.filter(id__lte=4).delete()
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>>> Article.objects.all()
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[<Article: Article 6>, <Article: Default headline>, <Article: Article 7>, <Article: Updated article 8>]
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"""}
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from django.conf import settings
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building_docs = getattr(settings, 'BUILDING_DOCS', False)
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if building_docs or settings.DATABASE_ENGINE == 'postgresql':
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__test__['API_TESTS'] += """
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# In PostgreSQL, microsecond-level precision is available.
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>>> a9 = Article(headline='Article 9', pub_date=datetime(2005, 7, 31, 12, 30, 45, 180))
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>>> a9.save()
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>>> Article.objects.get(id__exact=9).pub_date
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datetime.datetime(2005, 7, 31, 12, 30, 45, 180)
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"""
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if building_docs or settings.DATABASE_ENGINE == 'mysql':
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__test__['API_TESTS'] += """
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# In MySQL, microsecond-level precision isn't available. You'll lose
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# microsecond-level precision once the data is saved.
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>>> a9 = Article(headline='Article 9', pub_date=datetime(2005, 7, 31, 12, 30, 45, 180))
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>>> a9.save()
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>>> Article.objects.get(id__exact=9).pub_date
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datetime.datetime(2005, 7, 31, 12, 30, 45)
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"""
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__test__['API_TESTS'] += """
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# You can manually specify the primary key when creating a new object.
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>>> a101 = Article(id=101, headline='Article 101', pub_date=datetime(2005, 7, 31, 12, 30, 45))
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>>> a101.save()
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>>> a101 = Article.objects.get(pk=101)
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>>> a101.headline
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'Article 101'
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# You can create saved objects in a single step
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>>> a10 = Article.objects.create(headline="Article 10", pub_date=datetime(2005, 7, 31, 12, 30, 45))
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>>> Article.objects.get(headline="Article 10")
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<Article: Article 10>
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"""
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