Developing custom QuerySet methods

https://github.com/chibisov/events-site-example

Transcript

1. Developing  custom  QuerySet   methods   Chibisov  Gennady  
2. https://github.com/chibisov/events-site-example !
3. Model  methods   1. Instance  methods   2. Class  methods   3. QuerySet  methods   4. Manager  methods  
4. Instance  methods   class Event(models.Model): ! name = models.CharField(max_length=255)! slug = models.SlugField(unique=True)! date_start = models.DateTimeField()! ! def __unicode__(self):! return self.name ! ! @property! def is_published(self):! # uses current instance data! return (self.date_start <=! datetime.datetime.now())! ! ! >>> yac2012 = Event.objects.get(slug='yac2012')! >>> yac2012.__unicode__()! 'Yet another Conference 2012'! >>> yac2012.is_published! True!  
5. Class  methods   class Event(models.Model): ! name = models.CharField(max_length=255)! slug = models.SlugField(unique=True)! date_start = models.DateTimeField()! ! @classmethod! def get_fields_for_csv(cls):! return ['name', 'slug']! ! ! >>> Event.get_fields_for_csv()! ['name', 'slug']!  
6. QuerySet  methods   Event.objects.filter(id__lte=10).delete()!
7. QuerySet  methods   Event.objects.all().get_or_create(…)! Event.objects.all().create(…)! Event.objects.all().bulk_create(…)  
8. Manager  methods   class RegionManager(models.Manager):! def sync_with_geobase(self):! for region in regions_from_geobase():! try:! region_instance = self.model.objects.get(geobase_id=region.id)! # can modify any instance! region_instance.name_ru = region.name! region_instance.name_en = region.ename! region_instance.save()! except self.model.DoesNotExist:! # can create new instances! region_instance = self.model.objects.create(! geobase_id=region, ! name_ru=region.name, ! name_en=region.ename! )! # can remove instance! if region.is_deprecated:! region_instance.delete()! ! ! >>> Region.objects.sync_with_geobase()!
9. Manager  methods   # app/management/commands/sync_with_geobase.py! class Command(BaseCommand):! help = u"""Syncs regions with geobase"""! ! def handle(self, *args, **options):! Region.objects.sync_with_geobase()! ! ! $ ./manage.py sync_with_geobase! !
10. This  talk   1. Instance  methods   2. Class  methods   3. QuerySet  methods   4. Manager  methods  
11. What  for?  
12. What  for?   1. Readability  
13. Readability  L   events = Events.objects.all()! # filter for current site type! if settings.IS_INTERNAL_SITE:! events = events.filter(! Q(is_published_external=True) | ! Q(is_published_internal=True)! )! else:! events = events.filter(! is_published_for_external=True! )!
14. Readability  J   events = Events.objects.filter_for_current_site_type()!
15. Readability  L   yac2012 = Events.objects.get(slug='yac2012')! ! # is for current site type?! if settings.IS_INTERNAL_SITE:! is_for = (yac2012.is_published_for_internal ! and yac2012.is_published_for_external)! else:! is_for = yac2012.is_published_for_external!
16. Readability  J   yac2012.is_for_current_site_type!
17. What  for?   1. Readability   2. Reusability  
18. Reusability  J   class EventDetailView(DetailView): ! queryset = (Event.objects! .filter_for_current_site_type())! ! ! class EventListView(ListView):! queryset = (Event.objects! .filter_for_current_site_type())!
19. First  manager   # apps/events/managers.py ! from datetime.datetime import now! from django.db.models.query import QuerySet! from django.db import models! ! ! class EventQuerySet(QuerySet):! def filter_by_published(self):! return self.filter(date_start__lte=now())! ! ! class EventManager(models.Manager):! def get_query_set(self):! return EventQuerySet(self.model, ! using=self._db)!
20. First  manager   # apps/events/models.py! from django.db import models! from apps.events.managers import EventManager! ! ! class Event(models.Model):! name = models.CharField(max_length=255)! slug = models.SlugField(unique=True)! date_start = models.DateTimeField()! ! objects = EventManager()!
21. First  manager   >>> Event.objects.all().filter_by_published()! ! [<Event: Yet another Conference 2012>, ! <Event: iSubbotnik in Moscow 2012>]!
22. Oops…   >>> Event.objects.filter_by_published()! ! Traceback (most recent call last):! File "<console>", line 1, in <module>! AttributeError: 'EventManager' object has no attribute 'filter_by_published'!
23. Add  proxy  method   class EventManager(models.Manager):! def get_query_set(self):! return EventQuerySet(self.model, ! using=self._db)! ! def filter_by_published(self):! return (self.get_query_set()! .filter_by_published())!
24. Or  try  to  proxy  all  not  found   class EventManager(models.Manager):! def get_query_set(self):! return EventQuerySet(self.model, ! using=self._db)! ! def __getattr__(self, name):! if name.startswith('_'):! raise AttributeError(name)! else:! return getattr(self.get_query_set(), ! name)!
25. OK   >>> Event.objects.filter_by_published()! ! [<Event: Yet another Conference 2012>, ! <Event: iSubbotnik in Moscow 2012>]!
26. More   docs.djangoproject.com/en/dev/topics/db/managers/!
27. apps.events.models   class EventType(models.Model):! """! Example: Yet Another Conference! """! name = models.CharField(max_length=255)! slug = models.SlugField(unique=True)! is_moderated = models.BooleanField(default=False)!
28. /events/   •  Yet  another  Conference   •  I.Subbotnik   •  ECIR  
29. apps.events.models   class Event(models.Model):! """! Example: Yac 2012! """! name = models.CharField(max_length=255)! slug = models.SlugField(unique=True)! type = models.ForeignKey(EventType)! date_start = models.DateTimeField()!
30. /events/yac/   •  Yac  2010   •  Yac  2011   •  Yac  2012  
31. /events/yac/2012/  
32. /events/   class EventTypeListView(ListView):! queryset = EventType.objects.all()!  
33. /events/   •  Yet  another  Conference   •  I.Subbotnik   •  ECIR  (not  moderated)  
34. EventType  QuerySet  method   class EventTypeQuerySet(QuerySet):! def filter_by_published(self):! return self.filter(is_moderated=True)! !
35. /events/   class EventTypeListView(ListView):! queryset = (EventType.objects! .filter_by_published())!  
36. /events/   •  Yet  another  Conference   •  I.Subbotnik  
37. /events/yac/   •  Yac  2010   •  Yac  2011   •  Yac  2012  (too  early)  
38. Event  QuerySet  method   import datetime! from datetime.datetime import now! ! class EventQuerySet(QuerySet):! def filter_by_it_time_to_publish(self):! d = now() + datetime.timedelta(days=2)! return self.filter(date_start__lte=d)!
39. /events/yac/   class EventTypeDetailView(DetailView):! queryset = (EventType.objects! .filter_by_published())!  
40. /events/yac/   # /templates/events/eventtype_detail.html! ! {% for e in object.event_set! .filter_by_it_time_to_publish %}! <p>{{ e }}</p>! {% endfor %}!
41. /events/yac/   •  Yac  2010   •  Yac  2011  
42. /events/yac/2012/  
43. /events/yac/2012/   Show  if    
44. /events/yac/2012/   Show  if   •  It  is  Tme  to  publish  
45. /events/yac/2012/   Show  if   •  It  is  Tme  to  publish   •  Yac  EventType  is  published  
46. /events/yac/2012/   else   404  
47. /events/yac/2012/   class EventDetailView(DetailView):! queryset = (Event.objects! .filter_by_it_time_to_publish())! !
48. /events/yac/2012/   class EventDetailView(DetailView):! queryset = (Event.objects! .filter_by_it_time_to_publish())! ! def get_queryset(self):! q = super(EventDetailView, ! self).get_queryset()! return q.filter(type__is_moderated=True)!
49. L     EventType.objects.filter_by_published()   not  reused  
50. /events/yac/2012/   class EventDetailView(DetailView):! queryset = (Event.objects! .filter_by_it_time_to_publish())! ! def get_queryset(self):! q = super(EventDetailView, ! self).get_queryset()!
51. /events/yac/2012/   class EventDetailView(DetailView):! queryset = (Event.objects! .filter_by_it_time_to_publish())! ! def get_queryset(self):! q = super(EventDetailView, ! self).get_queryset()! pks = (EventType.objects! .filter_by_published()! .values_list('pk', flat=True))!
52. /events/yac/2012/   class EventDetailView(DetailView):! queryset = (Event.objects! .filter_by_it_time_to_publish())! ! def get_queryset(self):! q = super(EventDetailView, ! self).get_queryset()! pks = (EventType.objects! .filter_by_published()! .values_list('pk', flat=True))! return q.filter(type__pk__in=pks)!
53. L     2  DB  queries   Ugly  
54. /events/yac/2012/   class EventDetailView(DetailView):! queryset = (Event.objects! .filter_by_published())!
55. Pre\y   1  query   Reuse  filter_by_published  
56. HOW?  
57. Q  object  
58. class EventTypeQuerySet(QuerySet):! def filter_by_published(self):! return self.filter(Q(is_moderated=True))! ! ! class EventQuerySet(QuerySet):! ...! def filter_by_with_published_type(self):! return self.filter(Q(type__is_moderated=True))!
59. class EventTypeQuerySet(QuerySet):! def filter_by_published(self):! return self.filter(Q(is_moderated=True))! ! ! class EventQuerySet(QuerySet):! ...! def filter_by_with_published_type(self):! return self.filter(Q(type__is_moderated=True))! Diff  
60. class EventTypeConditions(object):! @classmethod! def is_published(cls):! return Q(is_moderated=True)! Move  Q  to  funcTon  
61. class EventTypeConditions(object):! @classmethod! def is_published(cls, prefix=None): ! return Q(is_moderated=True)! Prefix  as  param  
62. class EventTypeConditions(object):! @classmethod! def is_published(cls, prefix=None):! if prefix:! field = '%s__is_moderated' % prefix! else:! field = 'is_moderated'! ! return Q(is_moderated=True)! Field  name  with  prefix  
63. class EventTypeConditions(object):! @classmethod! def is_published(cls, prefix=None):! if prefix:! field = '%s__is_moderated' % prefix! else:! field = 'is_moderated'! ! return Q(**{field: True})! Use  prefixed  field  
64. >>> EventTypeConditions.is_published()!
65. >>> EventTypeConditions.is_published()! Q(is_moderated=True)!
66. >>> EventTypeConditions.is_published()! Q(is_moderated=True)! ! >>> EventTypeConditions.is_published(! ... prefix='type'! ... )!
67. >>> EventTypeConditions.is_published()! Q(is_moderated=True)! ! >>> EventTypeConditions.is_published(! ... prefix='type'! ... )! Q(type__is_moderated=True)!
68. class EventTypeQuerySet(QuerySet):! def filter_by_published(self):! return self.filter(! EventTypeConditions.is_published()! )! Use  it  for  EventType  
69. May  I?   class EventQuerySet(QuerySet):! ...! def filter_by_with_published_type(self):! return self.filter(! EventTypeConditions.is_published(! prefix='type’! )! )!
70. NO  
71. NO   EventTypeCondiTons  is   for  EventType  
72. NO   EventTypeCondiTons  is   for  EventType   Create   EventCondiTons  for  Event  
73. class EventConditions(object):! @classmethod! def is_with_published_type(cls):! event_prefix = 'type' ! return EventTypeConditions.is_published(! prefix=event_prefix! ) ! Create  Event  condiTons  
74. class EventConditions(object):! @classmethod! def is_with_published_type(cls, prefix=None): ! event_prefix = 'type' ! return EventTypeConditions.is_published(! prefix=event_prefix! )! Prefix  as  param  
75. class EventConditions(object):! @classmethod! def is_with_published_type(cls, prefix=None):! event_prefix = 'type' ! if prefix:! prefix = '%s__%s' % prefix, event_prefix! else:! prefix = event_prefix! ! return EventTypeConditions.is_published(! prefix=event_prefix! )! Add  prefix  
76. class EventConditions(object):! @classmethod! def is_with_published_type(cls, prefix=None): event_prefix = 'type'! if prefix:! prefix = '%s__%s' % prefix, event_prefix! else:! prefix = event_prefix! ! return EventTypeConditions.is_published(! prefix=prefix! )! Use  prefix  
77. >>> EventConditions.is_with_published_type()!
78. >>> EventConditions.is_with_published_type()! Q(type__is_moderated=True)! !
79. >>> EventConditions.is_with_published_type()! Q(type__is_moderated=True)! ! >>> EventConditions.is_with_published_type(! ... prefix=’event’! ... )!
80. >>> EventConditions.is_with_published_type()! Q(type__is_moderated=True)! ! >>> EventConditions.is_with_published_type(! ... prefix=’event’! ... )! Q(event__type__is_moderated=True)!
81. Use  it  for  Event   class EventQuerySet(QuerySet):! ...! def filter_by_with_published_type(self):! return self.filter(! EventConditions.is_with_published_type()! )!
82. Lets  refactor   class EventQuerySet(QuerySet):! ...! def filter_by_it_time_to_publish(self):! d = now() + datetime.timedelta(days=2)! return self.filter(date_start__lte=d)!
83. class EventConditions(object):! @classmethod! def is_with_published_type(cls, prefix=None):! ...! ! @classmethod! def is_it_time_to_publish(cls, prefix=None): ! if prefix:! field = '%s__date_start__lte' % prefix! else:! field = 'date_start__lte'! ! d = now() + datetime.timedelta(days=2) ! return Q(**{field: d})!
84. Aaer  refactor   class EventQuerySet(QuerySet):! ...! def filter_by_it_time_to_publish(self):! return self.filter(! EventConditions.is_it_time_to_publish()! )!
85. Combining  methods  
86. class EventConditions(object):! @classmethod! def is_with_published_type(cls, prefix=None):! ...! ! @classmethod! def is_it_time_to_publish(cls, prefix=None): ! ...!
87. class EventConditions(object):! @classmethod! def is_with_published_type(cls, prefix=None):! ...! ! @classmethod! def is_it_time_to_publish(cls, prefix=None): ! ...! ! @classmethod! def is_published(cls, prefix=None):! return (! cls.is_with_published_type(prefix) & ! cls.is_it_time_to_publish(prefix)! )! !
88. >>> EventConditions.is_published()! !
89. >>> EventConditions.is_published()! Q(date_start__lte=datetime(23,11,2012)) &! Q(type__is_moderated=True)! !
90. >>> EventConditions.is_published()! Q(date_start__lte=datetime(23,11,2012)) &! Q(type__is_moderated=True)! ! >>> EventConditions.is_published(! ... prefix=’event’! ... )!
91. >>> EventConditions.is_published()! Q(date_start__lte=datetime(23,11,2012)) &! Q(type__is_moderated=True)! ! >>> EventConditions.is_published(! ... prefix=’event’! ... )! Q(event__date_start__lte=datetime(23,11,2012))&! Q(event__type__is_moderated=True)!
92. Model  instance  methods  
93.     How  to  reuse  condiTons?  
94. How  to  reuse  condiTons?   class  Event(models.Model):          ...          @property          def  is_with_published_type(self):                  return  EventConditions.is_with_published_type(model_instance=self)            @property          def  is_it_time_to_publish(self):                  return  EventConditions.is_it_time_to_publish(model_instance=self)            @property          def  is_published(self):                  return  EventConditions.is_published(model_instance=self)!
95. True  and  False   =   True  &  False       How  to  reuse  condiTons?  
96. True  or  False   =   True  |  False       How  to  reuse  condiTons?  
97. More   https://github.com/chibisov/events-site-example ! /apps/accounts/models.py   /apps/accounts/managers.py     /apps/events/models.py   /apps/events/managers.py    
98. How  to  test  
99. Use  makers   •  make_published   •  make_not_published  
100. Use  makers   class TestEventIsPublished(TestConditionBase):! def test_1(self):! makers.event.make_with_published_type(self.instance)! makers.event.make_it_time_to_publish(self.instance)! ! self.assertConditionTrue(msg=msg)! ! def test_2(self):! makers.event.make_with_published_type(self.instance)! makers.event.make_not_it_time_to_publish(self.instance)! ! self.assertConditionFalse(msg=msg)! ! def test_3(self):! makers.event.make_it_time_to_publish(self.instance)! makers.event.make_not_with_published_type(self.instance)! ! self.assertConditionFalse(msg=msg)!
101. More   https://github.com/chibisov/events-site-example ! /apps/accounts/makers/   /apps/accounts/tests/condiTons/     /apps/events/makers/   /apps/events/tests/condiTons/    
102. class DistributionSendedConditions(object):! @classmethod! def is_ready_to_start_with_in_progress_status(cls, prefix=None):! k = {! 'prefix': prefix! }! ! return (! (cls.is_with_status(status='in_progress', **k)) &! ((cls.is_last_message_sended_more_than_5_minutes_ago(**k)) |! (cls.is_not_has_messages(**k) & ! cls.is_started_sending_more_than_5_minutes_ago(**k)))! )! More  complex  condiTons  
103. Спасибо