"""

7. The lookup API

This demonstrates features of the database API.

"""

from django.db import models

class Article(models.Model):

    headline = models.CharField(maxlength=100)

    pub_date = models.DateTimeField()

    class Meta:

        ordering = ('-pub_date', 'headline')

    def __str__(self):

        return self.headline

__test__ = {'API_TESTS':r"""

# Create a couple of Articles.

>>> from datetime import datetime

>>> a1 = Article(headline='Article 1', pub_date=datetime(2005, 7, 26))

>>> a1.save()

>>> a2 = Article(headline='Article 2', pub_date=datetime(2005, 7, 27))

>>> a2.save()

>>> a3 = Article(headline='Article 3', pub_date=datetime(2005, 7, 27))

>>> a3.save()

>>> a4 = Article(headline='Article 4', pub_date=datetime(2005, 7, 28))

>>> a4.save()

>>> a5 = Article(headline='Article 5', pub_date=datetime(2005, 8, 1, 9, 0))

>>> a5.save()

>>> a6 = Article(headline='Article 6', pub_date=datetime(2005, 8, 1, 8, 0))

>>> a6.save()

>>> a7 = Article(headline='Article 7', pub_date=datetime(2005, 7, 27))

>>> a7.save()

# Each QuerySet gets iterator(), which is a generator that "lazily" returns

# results using database-level iteration.

>>> for a in Article.objects.iterator():

...     print a.headline

Article 5

Article 6

Article 4

Article 2

Article 3

Article 7

Article 1

# iterator() can be used on any QuerySet.

>>> for a in Article.objects.filter(headline__endswith='4').iterator():

...     print a.headline

Article 4

# count() returns the number of objects matching search criteria.

>>> Article.objects.count()

7L

>>> Article.objects.filter(pub_date__exact=datetime(2005, 7, 27)).count()

3L

>>> Article.objects.filter(headline__startswith='Blah blah').count()

0L

# count() should respect sliced query sets.

>>> articles = Article.objects.all()

>>> articles.count()

7L

>>> articles[:4].count()

4

>>> articles[1:100].count()

6L

>>> articles[10:100].count()

0

# Date and date/time lookups can also be done with strings.

>>> Article.objects.filter(pub_date__exact='2005-07-27 00:00:00').count()

3L

# in_bulk() takes a list of IDs and returns a dictionary mapping IDs

# to objects.

>>> Article.objects.in_bulk([1, 2])

{1: <Article: Article 1>, 2: <Article: Article 2>}

>>> Article.objects.in_bulk([3])

{3: <Article: Article 3>}

>>> Article.objects.in_bulk([1000])

{}

>>> Article.objects.in_bulk([])

{}

>>> Article.objects.in_bulk('foo')

Traceback (most recent call last):

    ...

AssertionError: in_bulk() must be provided with a list of IDs.

>>> Article.objects.in_bulk()

Traceback (most recent call last):

    ...

TypeError: in_bulk() takes exactly 2 arguments (1 given)

>>> Article.objects.in_bulk(headline__startswith='Blah')

Traceback (most recent call last):

    ...

TypeError: in_bulk() got an unexpected keyword argument 'headline__startswith'

# values() returns a list of dictionaries instead of object instances -- and

# you can specify which fields you want to retrieve.

>>> Article.objects.values('headline')

[{'headline': 'Article 5'}, {'headline': 'Article 6'}, {'headline': 'Article 4'}, {'headline': 'Article 2'}, {'headline': 'Article 3'}, {'headline': 'Article 7'}, {'headline': 'Article 1'}]

>>> Article.objects.filter(pub_date__exact=datetime(2005, 7, 27)).values('id')

[{'id': 2}, {'id': 3}, {'id': 7}]

>>> list(Article.objects.values('id', 'headline')) == [{'id': 5, 'headline': 'Article 5'}, {'id': 6, 'headline': 'Article 6'}, {'id': 4, 'headline': 'Article 4'}, {'id': 2, 'headline': 'Article 2'}, {'id': 3, 'headline': 'Article 3'}, {'id': 7, 'headline': 'Article 7'}, {'id': 1, 'headline': 'Article 1'}]

True

>>> for d in Article.objects.values('id', 'headline'):

...     i = d.items()

...     i.sort()

...     i

[('headline', 'Article 5'), ('id', 5)]

[('headline', 'Article 6'), ('id', 6)]

[('headline', 'Article 4'), ('id', 4)]

[('headline', 'Article 2'), ('id', 2)]

[('headline', 'Article 3'), ('id', 3)]

[('headline', 'Article 7'), ('id', 7)]

[('headline', 'Article 1'), ('id', 1)]

# You can use values() with iterator() for memory savings, because iterator()

# uses database-level iteration.

>>> for d in Article.objects.values('id', 'headline').iterator():

...     i = d.items()

...     i.sort()

...     i

[('headline', 'Article 5'), ('id', 5)]

[('headline', 'Article 6'), ('id', 6)]

[('headline', 'Article 4'), ('id', 4)]

[('headline', 'Article 2'), ('id', 2)]

[('headline', 'Article 3'), ('id', 3)]

[('headline', 'Article 7'), ('id', 7)]

[('headline', 'Article 1'), ('id', 1)]

# if you don't specify which fields, all are returned

>>> list(Article.objects.filter(id=5).values()) == [{'id': 5, 'headline': 'Article 5', 'pub_date': datetime(2005, 8, 1, 9, 0)}]

True

# Every DateField and DateTimeField creates get_next_by_FOO() and

# get_previous_by_FOO() methods.

# In the case of identical date values, these methods will use the ID as a

# fallback check. This guarantees that no records are skipped or duplicated.

>>> a1.get_next_by_pub_date()

<Article: Article 2>

>>> a2.get_next_by_pub_date()

<Article: Article 3>

>>> a2.get_next_by_pub_date(headline__endswith='6')

<Article: Article 6>

>>> a3.get_next_by_pub_date()

<Article: Article 7>

>>> a4.get_next_by_pub_date()

<Article: Article 6>

>>> a5.get_next_by_pub_date()

Traceback (most recent call last):

    ...

DoesNotExist: Article matching query does not exist.

>>> a6.get_next_by_pub_date()

<Article: Article 5>

>>> a7.get_next_by_pub_date()

<Article: Article 4>

>>> a7.get_previous_by_pub_date()

<Article: Article 3>

>>> a6.get_previous_by_pub_date()

<Article: Article 4>

>>> a5.get_previous_by_pub_date()

<Article: Article 6>

>>> a4.get_previous_by_pub_date()

<Article: Article 7>

>>> a3.get_previous_by_pub_date()

<Article: Article 2>

>>> a2.get_previous_by_pub_date()

<Article: Article 1>

# Underscores and percent signs have special meaning in the underlying

# SQL code, but Django handles the quoting of them automatically.

>>> a8 = Article(headline='Article_ with underscore', pub_date=datetime(2005, 11, 20))

>>> a8.save()

>>> Article.objects.filter(headline__startswith='Article')

[<Article: Article_ with underscore>, <Article: Article 5>, <Article: Article 6>, <Article: Article 4>, <Article: Article 2>, <Article: Article 3>, <Article: Article 7>, <Article: Article 1>]

>>> Article.objects.filter(headline__startswith='Article_')

[<Article: Article_ with underscore>]

>>> a9 = Article(headline='Article% with percent sign', pub_date=datetime(2005, 11, 21))

>>> a9.save()

>>> Article.objects.filter(headline__startswith='Article')

[<Article: Article% with percent sign>, <Article: Article_ with underscore>, <Article: Article 5>, <Article: Article 6>, <Article: Article 4>, <Article: Article 2>, <Article: Article 3>, <Article: Article 7>, <Article: Article 1>]

>>> Article.objects.filter(headline__startswith='Article%')

[<Article: Article% with percent sign>]

# exclude() is the opposite of filter() when doing lookups:

>>> Article.objects.filter(headline__contains='Article').exclude(headline__contains='with')

[<Article: Article 5>, <Article: Article 6>, <Article: Article 4>, <Article: Article 2>, <Article: Article 3>, <Article: Article 7>, <Article: Article 1>]

>>> Article.objects.exclude(headline__startswith="Article_")

[<Article: Article% with percent sign>, <Article: Article 5>, <Article: Article 6>, <Article: Article 4>, <Article: Article 2>, <Article: Article 3>, <Article: Article 7>, <Article: Article 1>]

>>> Article.objects.exclude(headline="Article 7")

[<Article: Article% with percent sign>, <Article: Article_ with underscore>, <Article: Article 5>, <Article: Article 6>, <Article: Article 4>, <Article: Article 2>, <Article: Article 3>, <Article: Article 1>]

# Backslashes also have special meaning in the underlying SQL code, but Django

# automatically quotes them appropriately.

>>> a10 = Article(headline='Article with \\ backslash', pub_date=datetime(2005, 11, 22))

>>> a10.save()

>>> Article.objects.filter(headline__contains='\\')

[<Article: Article with \ backslash>]

# none() returns an EmptyQuerySet that behaves like any other QuerySet object

>>> Article.objects.none()

[]

>>> Article.objects.none().filter(headline__startswith='Article')

[]

>>> Article.objects.none().count()

0

>>> [article for article in Article.objects.none().iterator()]

[]

# using __in with an empty list should return an empty query set

>>> Article.objects.filter(id__in=[])

[]

>>> Article.objects.exclude(id__in=[])

[<Article: Article with \ backslash>, <Article: Article% with percent sign>, <Article: Article_ with underscore>, <Article: Article 5>, <Article: Article 6>, <Article: Article 4>, <Article: Article 2>, <Article: Article 3>, <Article: Article 7>, <Article: Article 1>]

# Programming errors are pointed out with nice error messages

>>> Article.objects.filter(pub_date_year='2005').count()

Traceback (most recent call last):

    ...

TypeError: Cannot resolve keyword 'pub_date_year' into field

>>> Article.objects.filter(headline__starts='Article')

Traceback (most recent call last):

    ...

TypeError: Cannot resolve keyword 'headline__starts' into field

"""}