mirror of https://github.com/django/django.git
68 lines
2.4 KiB
Python
68 lines
2.4 KiB
Python
"""
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6. Specifying ordering
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Specify default ordering for a model using the ``ordering`` attribute, which
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should be a list or tuple of field names. This tells Django how to order the
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results of ``get_list()`` and other similar functions.
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If a field name in ``ordering`` starts with a hyphen, that field will be
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ordered in descending order. Otherwise, it'll be ordered in ascending order.
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The special-case field name ``"?"`` specifies random order.
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The ordering attribute is not required. If you leave it off, ordering will be
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undefined -- not random, just undefined.
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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)
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pub_date = models.DateTimeField()
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class Meta:
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ordering = ('-pub_date', 'headline')
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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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# Create a couple of Articles.
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>>> from datetime import datetime
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>>> a1 = Article(headline='Article 1', pub_date=datetime(2005, 7, 26))
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>>> a1.save()
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>>> a2 = Article(headline='Article 2', pub_date=datetime(2005, 7, 27))
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>>> a2.save()
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>>> a3 = Article(headline='Article 3', pub_date=datetime(2005, 7, 27))
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>>> a3.save()
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>>> a4 = Article(headline='Article 4', pub_date=datetime(2005, 7, 28))
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>>> a4.save()
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# By default, Article.objects.all() orders by pub_date descending, then
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# headline ascending.
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>>> Article.objects.all()
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[<Article: Article 4>, <Article: Article 2>, <Article: Article 3>, <Article: Article 1>]
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# Override ordering with order_by, which is in the same format as the ordering
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# attribute in models.
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>>> Article.objects.order_by('headline')
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[<Article: Article 1>, <Article: Article 2>, <Article: Article 3>, <Article: Article 4>]
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>>> Article.objects.order_by('pub_date', '-headline')
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[<Article: Article 1>, <Article: Article 3>, <Article: Article 2>, <Article: Article 4>]
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# Use the 'stop' part of slicing notation to limit the results.
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>>> Article.objects.order_by('headline')[:2]
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[<Article: Article 1>, <Article: Article 2>]
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# Use the 'stop' and 'start' parts of slicing notation to offset the result list.
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>>> Article.objects.order_by('headline')[1:3]
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[<Article: Article 2>, <Article: Article 3>]
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# Getting a single item should work too:
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>>> Article.objects.all()[0]
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<Article: Article 4>
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# Use '?' to order randomly. (We're using [...] in the output to indicate we
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# don't know what order the output will be in.
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>>> Article.objects.order_by('?')
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[...]
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"""}
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