The django book - Chap10 : Advanced Models

1. Advanced Models 「The Django Book」 Chapter 10 Spin Lai July 23, 2013 2013年7月24日星期三

2. 賴司平 (Spin) 資拓宏宇氣象科技事業處 PHP、Javascript、Python About me 2013年7月24日星期三

3. Related objects Update database schema Model methods Managers Execute raw SQL queries More about Managers Today’s topics 2013年7月24日星期三

4. Related objects 2013年7月24日星期三

5. Recalling the Chapter 5 ... 2013年7月24日星期三

6. Publisher id name address city state_province country website AutoField CharField CharField CharField CharField CharField URLField Book id title authors publisher publication_date AutoField CharField ManyToManyField ForeignKey DateField Author id ﬁrst_name last_name email AutoField CharField CharField EmailField N:1N:M 2013年7月24日星期三

7. class Publisher(models.Model): name = models.CharField(max_length=30) address = models.CharField(max_length=50) city = models.CharField(max_length=60) state_province = models.CharField(max_length=30) country = models.CharField(max_length=50) website = models.URLField() def __unicode__(self): return self.name 2013年7月24日星期三

8. class Author(models.Model): first_name = models.CharField(max_length=30) last_name = models.CharField(max_length=40) email = models.EmailField() def __unicode__(self): return u'%s %s' % (self.first_name, self.last_name) 2013年7月24日星期三

9. class Book(models.Model): title = models.CharField(max_length=100) authors = models.ManyToManyField(Author) publisher = models.ForeignKey(Publisher) publication_date = models.DateField() def __unicode__(self): return self.title 2013年7月24日星期三

11. Foreign Key Value Publisher id name address city state_province country website AutoField CharField CharField CharField CharField CharField URLField Book id title authors publisher AutoField CharField ManyToManyField ForeignKey >>> b = Book.objects.get(id=50) >>> b.publisher <Publisher: Apress Publishing> >>> b.publisher.website u'http://www.apress.com/' <Publisher: Apress Publishing> 2013年7月24日星期三

12. Foreign Key Value Publisher id name address city state_province country website AutoField CharField CharField CharField CharField CharField URLField Book id title authors publisher AutoField CharField ManyToManyField ForeignKey >>> p = Publisher.objects.get(name='Apress Publishing') >>> p.book_set.all() [<Book: The Django Book>, <Book: Dive Into Python>, ...] >>> p.book_set.filter(name__icontains='django') [<Book: The Django Book>, <Book: Pro Django>] 2013年7月24日星期三

13. Foreign Key Value Publisher id name address city state_province country website AutoField CharField CharField CharField CharField CharField URLField Book id title authors publisher AutoField CharField ManyToManyField ForeignKey >>> p = Publisher.objects.get(name='Apress Publishing') >>> p.book_set.all() [<Book: The Django Book>, <Book: Dive Into Python>, ...] >>> p.book_set.filter(name__icontains='django') [<Book: The Django Book>, <Book: Pro Django>] 2013年7月24日星期三

16. Many-to-Many Values Author id ﬁrst_name last_name email AutoField CharField CharField EmailField Book id title authors publisher AutoField CharField ManyToManyField ForeignKey >>> b = Book.objects.get(id=50) >>> b.authors.all() [<Author: Adrian Holovaty>, <Author: Jacob Kaplan-Moss>] >>> b.authors.filter (first_name='Adrian') [<Author: Adrian Holovaty>] >>> b.authors.filter (first_name='Adam') [] 2013年7月24日星期三

17. Many-to-Many Values Author id ﬁrst_name last_name email AutoField CharField CharField EmailField Book id title authors publisher AutoField CharField ManyToManyField ForeignKey >>> a = Author.objects.get(first_name='Adrian', last_name='Holovaty') >>> a.book_set.all() [<Book: The Django Book>, <Book: Adrian's Other Book>]' 2013年7月24日星期三

18. Many-to-Many Values Author id ﬁrst_name last_name email AutoField CharField CharField EmailField Book id title authors publisher AutoField CharField ManyToManyField ForeignKey >>> a = Author.objects.get(first_name='Adrian', last_name='Holovaty') >>> a.book_set.all() [<Book: The Django Book>, <Book: Adrian's Other Book>]' 2013年7月24日星期三

19. Update database schema 2013年7月24日星期三

20. First of all 2013年7月24日星期三

21. Does not care extra DB table columns Does not care extra DB tables Complains if model contains ﬁelds that has not yet been created in the DB table Django 2013年7月24日星期三

22. `syncdb` only create tables for models which have not yet been installed. 2013年7月24日星期三

23. Add model fields Remove model fields Remove models Update database schema 2013年7月24日星期三

24. Add model ﬁelds 2013年7月24日星期三

25. Add model fields Add fields to the model Check the column definitions for new fields Add new columns to the DB table Verify new fields was added properly In development environments ... 2013年7月24日星期三

26. Add model fields Add fields to the model Check the column definitions for new fields Add new columns to the DB table Verify new fields was added properly In development environments ... class Book(models.Model): title = models.CharField(max_length=100) authors = models.ManyToManyField(Author) publisher = models.ForeignKey(Publisher) publication_date = models.DateField() num_pages = models.IntegerField(blank=True, null=True) def __unicode__(self): return self.title 2013年7月24日星期三

27. Add model fields Add fields to the model Check the column definitions for new fields Add new columns to the DB table Verify new fields was added properly In development environments ... CREATE TABLE "books_book" ( "id" serial NOT NULL PRIMARY KEY, "title" varchar(100) NOT NULL, "publisher_id" integer NOT NULL REFERENCES "books_publisher" ("id"), "publication_date" date NOT NULL, "num_pages" integer NULL ); $ python manage.py sqlall books 2013年7月24日星期三

28. Add model fields Add fields to the model Check the column definitions for new fields Add new columns to the DB table Verify new fields was added properly In development environments ... ALTER TABLE books_book ADD COLUMN num_pages integer; 2013年7月24日星期三

29. Add model fields Add fields to the model Check the column definitions for new fields Add new columns to the DB table Verify new fields was added properly In development environments ... >>> from mysite.books.models import Book >>> Book.objects.all()[:5] 2013年7月24日星期三

30. Add model ﬁelds Add new columns to the DB table Add ﬁelds to the model Restart the web server In production environments ... 2013年7月24日星期三

31. Remove model ﬁelds 2013年7月24日星期三

32. Add model fields Remove fields from the model Restart the web server Remove columns from the DB table Remove Normal fields ... 2013年7月24日星期三

33. Add model fields Remove fields from the model Restart the web server Remove columns from the DB table Remove Normal fields ... ALTER TABLE books_book DROP COLUMN num_pages; 2013年7月24日星期三

34. Add model fields Remove Many-to-Many fields from the model Restart the web server Remove Many-to-Many table from the DB Remove Many-to-Many fields ... 2013年7月24日星期三

35. Add model fields Remove Many-to-Many fields from the model Restart the web server Remove Many-to-Many table from the DB Remove Many-to-Many fields ... DROP TABLE books_book_authors; 2013年7月24日星期三

36. Remove models 2013年7月24日星期三

37. Remove model from the models.py Restart the web server Remove dependent tables from the DB Remove the target table from the DB Remove models 2013年7月24日星期三

38. Remove model from the `models.py` Restart the web server Remove dependent tables from the DB Remove the target table from the DB Remove models DROP TABLE books_book; 2013年7月24日星期三

39. Model methods 2013年7月24日星期三

40. class Person(models.Model): first_name = models.CharField(max_length=50) last_name = models.CharField(max_length=50) birth_date = models.DateField() address = models.CharField(max_length=100) city = models.CharField(max_length=50) state = USStateField() # Yes, this is U.S.-centric... def baby_boomer_status(self): "Returns the person's baby-boomer status." import datetime if datetime.date(1945, 8, 1) <= self.birth_date <= datetime.date(1964, 12, 31): return "Baby boomer" if self.birth_date < datetime.date(1945, 8, 1): return "Pre-boomer" return "Post-boomer" def is_midwestern(self): "Returns True if this person is from the Midwest." return self.state in ('IL', 'WI', 'MI', 'IN', 'OH', 'IA', 'MO') def _get_full_name(self): "Returns the person's full name." return u'%s %s' % (self.first_name, self.last_name) full_name = property(_get_full_name) 2013年7月24日星期三

42. Model methods >>> p = Person.objects.get(first_name='Barack', last_name='Obama') >>> p.birth_date datetime.date(1961, 8, 4) >>> p.baby_boomer_status() 'Baby boomer' >>> p.is_midwestern() True 2013年7月24日星期三

44. Property methods >>> p = Person.objects.get(first_name='Barack', last_name='Obama') >>> p.full_name # Note this isn't a method u'Barack Obama' 2013年7月24日星期三

45. Managers 2013年7月24日星期三

46. What is Manager? 2013年7月24日星期三

47. Manager Book.objects.all() 2013年7月24日星期三

48. Manager Book.objects.all() 2013年7月24日星期三

49. Manager “ The interface through which database query operations are provided to Django models. ” 2013年7月24日星期三

50. Why do we need a custom Manager? 2013年7月24日星期三

51. Add extra Manager methods Modify initial Manager QuerySets Custom Mangers 2013年7月24日星期三

52. Add extra Manager methods 2013年7月24日星期三

53. Add extra Manager methods # Get the number of books that have a title ‘Django’ >>> Book.objects.filter(title__icontains='Django') # Get the number of books that have a title ‘Python’ >>> Book.objects.filter(title__icontains='Python') # Get the number of books that have a title ‘xxx’ .... # Get the number of books that have a title ‘yyy’ .... ..... ....... 2013年7月24日星期三

54. Add extra Manager methods # takes a keyword and returns the number of books >>> Book.objects.title_count('django') >>> Book.objects.title_count('python') 2013年7月24日星期三

55. # models.py from django.db import models # ... Author and Publisher models here ... class BookManager(models.Manager): def title_count(self, keyword): return self.filter(title__icontains=keyword).count() class Book(models.Model): title = models.CharField(max_length=100) authors = models.ManyToManyField(Author) publisher = models.ForeignKey(Publisher) publication_date = models.DateField() num_pages = models.IntegerField(blank=True, null=True) objects = BookManager() def __unicode__(self): return self.title 2013年7月24日星期三

56. # models.py from django.db import models # ... Author and Publisher models here ... class BookManager(models.Manager): def title_count(self, keyword): return self.filter(title__icontains=keyword).count() class Book(models.Model): title = models.CharField(max_length=100) authors = models.ManyToManyField(Author) publisher = models.ForeignKey(Publisher) publication_date = models.DateField() num_pages = models.IntegerField(blank=True, null=True) objects = BookManager() def __unicode__(self): return self.title 2013年7月24日星期三

57. Modify initial Manager QuerySets 2013年7月24日星期三

58. Modify initial Manager QuerySets Default Manager return all the records Override Manager’s base QuerySets 2013年7月24日星期三

59. Modify initial Manager QuerySets Default Manager return all the records Override Manager’s base QuerySets # returns all books in the book database >>> Book.objects.all() 2013年7月24日星期三

60. Modify initial Manager QuerySets Default Manager return all the records Override Manager’s base QuerySets By overriding the Manager.get_query_set() 2013年7月24日星期三

61. Modify initial Manager QuerySets from django.db import models # First, define the Manager subclass. class DahlBookManager(models.Manager): def get_query_set(self): return super(DahlBookManager, self).get_query_set() .filter(author='Roald Dahl') # Then hook it into the Book model explicitly. class Book(models.Model): title = models.CharField(max_length=100) author = models.CharField(max_length=50) # ... objects = models.Manager() # The default manager. dahl_objects = DahlBookManager() # The Dahl-specific manager. 2013年7月24日星期三

62. Modify initial Manager QuerySets from django.db import models # First, define the Manager subclass. class DahlBookManager(models.Manager): def get_query_set(self): return super(DahlBookManager, self).get_query_set() .filter(author='Roald Dahl') # Then hook it into the Book model explicitly. class Book(models.Model): title = models.CharField(max_length=100) author = models.CharField(max_length=50) # ... objects = models.Manager() # The default manager. dahl_objects = DahlBookManager() # The Dahl-specific manager. 2013年7月24日星期三

63. Modify initial Manager QuerySets >>> Book.dahl_objects.all() >>> Book.dahl_objects.filter(title='Matilda') >>> Book.dahl_objects.count() 2013年7月24日星期三

64. Another example class MaleManager(models.Manager): def get_query_set(self): return super(MaleManager, self).get_query_set().filter(sex='M') class FemaleManager(models.Manager): def get_query_set(self): return super(FemaleManager, self).get_query_set().filter(sex='F') class Person(models.Model): first_name = models.CharField(max_length=50) last_name = models.CharField(max_length=50) sex = models.CharField(max_length=1, choices=(('M', 'Male'), ('F', 'Female'))) people = models.Manager() men = MaleManager() women = FemaleManager() 2013年7月24日星期三

65. Another example class MaleManager(models.Manager): def get_query_set(self): return super(MaleManager, self).get_query_set().filter(sex='M') class FemaleManager(models.Manager): def get_query_set(self): return super(FemaleManager, self).get_query_set().filter(sex='F') class Person(models.Model): first_name = models.CharField(max_length=50) last_name = models.CharField(max_length=50) sex = models.CharField(max_length=1, choices=(('M', 'Male'), ('F', 'Female'))) people = models.Manager() men = MaleManager() women = FemaleManager() 2013年7月24日星期三

66. Modify initial Manager QuerySets >>> Person.men.all() >>> Person.women.all() >>> Person.people.all() 2013年7月24日星期三

67. Execute raw SQL queries 2013年7月24日星期三

68. Django DB objects 2013年7月24日星期三

69. connection object cursor object cursor.execute() cursor.fetchone() / cursor.fetchall() Implement the Python DB-API (PEP-0249) Django DB objects 2013年7月24日星期三

70. Execute raw SQL queries >>> from django.db import connection >>> cursor = connection.cursor() >>> cursor.execute(""" ... SELECT DISTINCT first_name ... FROM people_person ... WHERE last_name = %s""", ['Lennon']) >>> row = cursor.fetchone() >>> print row ['John'] 2013年7月24日星期三

71. Execute raw SQL queries class PersonManager(models.Manager): def first_names(self, last_name): cursor = connection.cursor() cursor.execute(""" SELECT DISTINCT first_name FROM people_person WHERE last_name = %s""", [last_name]) return [row[0] for row in cursor.fetchone()] class Person(models.Model): first_name = models.CharField(max_length=50) last_name = models.CharField(max_length=50) objects = PersonManager() 2013年7月24日星期三

74. Execute raw SQL queries >>> Person.objects.first_names('Lennon') ['John', 'Cynthia'] 2013年7月24日星期三

75. More about Managers 2013年7月24日星期三

76. As mentioned previously... 2013年7月24日星期三

77. Business logic encapsulation Add custom Managers Override default Manager with custom methods 2013年7月24日星期三

78. Add custom Managers class IncompleteTodoManager(models.Manager): def get_query_set(self): return super(TodoManager, self).get_query_set().filter(is_done=False) class HighPriorityTodoManager(models.Manager): def get_query_set(self): return super(TodoManager, self).get_query_set().filter(priority=1) class Todo(models.Model): content = models.CharField(max_length=100) # other fields go here.. objects = models.Manager() # the default manager # attach our custom managers: incomplete = models.IncompleteTodoManager() high_priority = models.HighPriorityTodoManager() 2013年7月24日星期三

79. Add custom Managers class IncompleteTodoManager(models.Manager): def get_query_set(self): return super(TodoManager, self).get_query_set().filter(is_done=False) class HighPriorityTodoManager(models.Manager): def get_query_set(self): return super(TodoManager, self).get_query_set().filter(priority=1) class Todo(models.Model): content = models.CharField(max_length=100) # other fields go here.. objects = models.Manager() # the default manager # attach our custom managers: incomplete = models.IncompleteTodoManager() high_priority = models.HighPriorityTodoManager() 2013年7月24日星期三

80. Add custom Managers >>> Todo.incomplete.all() >>> Todo.high_priority.all() 2013年7月24日星期三

81. But 2013年7月24日星期三

82. Drawbacks Verbose Managers Cluttered model namespace Not chainable 2013年7月24日星期三

83. Custom Manager methods 2013年7月24日星期三

84. Custom Manager methods class TodoManager(models.Manager): def incomplete(self): return self.filter(is_done=False) def high_priority(self): return self.filter(priority=1) class Todo(models.Model): content = models.CharField(max_length=100) # other fields go here.. objects = TodoManager() 2013年7月24日星期三

85. Custom Manager methods >>> Todo.objects.incomplete() >>> Todo.objects.high_priority() 2013年7月24日星期三

87. Drawbacks Not chainable between custom methods. # It didn’t work ! >>> Todo.objects.incomplete().high_priority() 2013年7月24日星期三

88. Custom QuerySets 2013年7月24日星期三

89. Custom QuerySets class TodoQuerySet(models.query.QuerySet): def incomplete(self): return self.filter(is_done=False) def high_priority(self): return self.filter(priority=1) class TodoManager(models.Manager): def get_query_set(self): return TodoQuerySet(self.model, using=self._db) class Todo(models.Model): content = models.CharField(max_length=100) # other fields go here.. objects = TodoManager() 2013年7月24日星期三

90. Custom QuerySets class TodoQuerySet(models.query.QuerySet): def incomplete(self): return self.filter(is_done=False) def high_priority(self): return self.filter(priority=1) class TodoManager(models.Manager): def get_query_set(self): return TodoQuerySet(self.model, using=self._db) class Todo(models.Model): content = models.CharField(max_length=100) # other fields go here.. objects = TodoManager() 2013年7月24日星期三

91. Custom QuerySets >>> Todo.objects.get_query_set().incomplete() >>> Todo.objects.get_query_set().high_priority() >>> # (or) >>> Todo.objects.all().incomplete() >>> Todo.objects.all().high_priority() >>> # Chainable !!! >>> Todo.objects.all().incomplete().high_priority() 2013年7月24日星期三

93. Custom QuerySets >>> Todo.objects.get_query_set().incomplete() >>> Todo.objects.get_query_set().high_priority() >>> # (or) >>> Todo.objects.all().incomplete() >>> Todo.objects.all().high_priority() >>> # Chainable !!! >>> Todo.objects.all().incomplete().high_priority() 2013年7月24日星期三

94. Custom QuerySets >>> Todo.objects.get_query_set().incomplete() >>> Todo.objects.get_query_set().high_priority() >>> # (or) >>> Todo.objects.all().incomplete() >>> Todo.objects.all().high_priority() >>> # Chainable !!! >>> Todo.objects.all().incomplete().high_priority() Ug==Ugly !! 2013年7月24日星期三

95. Proxy everything !! 2013年7月24日星期三

96. Proxy everything !! class TodoQuerySet(models.query.QuerySet): def incomplete(self): return self.filter(is_done=False) def high_priority(self): return self.filter(priority=1) class TodoManager(models.Manager): def get_query_set(self): return TodoQuerySet(self.model, using=self._db) def incomplete(self): return self.get_query_set().incomplete() def high_priority(self): return self.get_query_set().high_priority() 2013年7月24日星期三

97. Proxy everything !! class TodoQuerySet(models.query.QuerySet): def incomplete(self): return self.filter(is_done=False) def high_priority(self): return self.filter(priority=1) class TodoManager(models.Manager): def get_query_set(self): return TodoQuerySet(self.model, using=self._db) def incomplete(self): return self.get_query_set().incomplete() def high_priority(self): return self.get_query_set().high_priority() 2013年7月24日星期三

98. Proxy everything !! >>> Todo.objects.incomplete().high_priority() # Perfect !! 2013年7月24日星期三

99. Thank you 2013年7月24日星期三

The django book - Chap10 : Advanced Models

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