대화식 Python 쉘을 통해 Django API를 사용해볼 시간
$ python manage.py shell Python 3.8.3 (default, May 18 2020, 11:25:01) [GCC 7.5.0] on linux Type "help", "copyright", "credits" or "license" for more information. (InteractiveConsole) >>> from polls.models import Choice, Question >>> Question.objects.all() <QuerySet > >>> from django.utils import timezone >>> q = Question(question_text="What's new?", pub_date=timezone.now()) >>> q <Question: Question object (None)> >>> q.save() >>> q.id 1 >>> q.question_text "What's new?" >>> q.pub_date datetime.datetime(2021, 4, 13, 12, 48, 15, 294472, tzinfo=<UTC>) >>> q.question_text = "What's up?" >>> q.save() >>> Question.objects.all() <QuerySet [<Question: Question object (1)>]> >>>
Question object (1)은 객체 표현에 도움이 되지 않는다.
polls/models.py 파일의 Question 모델을 수정하여, __str__() 메소드를 Question과 Choice에 추가해보자
class Question(models.Model): question_text = models.CharField(max_length=200) pub_date = models.DateTimeField('date published') def __str__(self): return self.question_text
__str__() 메소드를 추가하는 것은 객체의 표현을 대화식 프롬프트에서 편하게 보려는 이유 말고도, Django가 자동으로 생성하는 관리 사이트에서도 객체의 표현이 사용하기 때문이다.
>>> from polls.models import Choice, Question # Make sure our __str__() addition worked. >>> Question.objects.all() <QuerySet [<Question: What's up?>]> # Django provides a rich database lookup API that's entirely driven by # keyword arguments. >>> Question.objects.filter(id=1) <QuerySet [<Question: What's up?>]> >>> Question.objects.filter(question_text__startswith='What') <QuerySet [<Question: What's up?>]> # Get the question that was published this year. >>> from django.utils import timezone >>> current_year = timezone.now().year >>> Question.objects.get(pub_date__year=current_year) <Question: What's up?> # Request an ID that doesn't exist, this will raise an exception. >>> Question.objects.get(id=2) Traceback (most recent call last): ... DoesNotExist: Question matching query does not exist. # Lookup by a primary key is the most common case, so Django provides a # shortcut for primary-key exact lookups. # The following is identical to Question.objects.get(id=1). >>> Question.objects.get(pk=1) <Question: What's up?> # Make sure our custom method worked. >>> q = Question.objects.get(pk=1) >>> q.was_published_recently() True # Give the Question a couple of Choices. The create call constructs a new # Choice object, does the INSERT statement, adds the choice to the set # of available choices and returns the new Choice object. Django creates # a set to hold the "other side" of a ForeignKey relation # (e.g. a question's choice) which can be accessed via the API. >>> q = Question.objects.get(pk=1) # Display any choices from the related object set -- none so far. >>> q.choice_set.all() <QuerySet > # Create three choices. >>> q.choice_set.create(choice_text='Not much', votes=0) <Choice: Not much> >>> q.choice_set.create(choice_text='The sky', votes=0) <Choice: The sky> >>> c = q.choice_set.create(choice_text='Just hacking again', votes=0) # Choice objects have API access to their related Question objects. >>> c.question <Question: What's up?> # And vice versa: Question objects get access to Choice objects. >>> q.choice_set.all() <QuerySet [<Choice: Not much>, <Choice: The sky>, <Choice: Just hacking again>]> >>> q.choice_set.count() 3 # The API automatically follows relationships as far as you need. # Use double underscores to separate relationships. # This works as many levels deep as you want; there's no limit. # Find all Choices for any question whose pub_date is in this year # (reusing the 'current_year' variable we created above). >>> Choice.objects.filter(question__pub_date__year=current_year) <QuerySet [<Choice: Not much>, <Choice: The sky>, <Choice: Just hacking again>]> # Let's delete one of the choices. Use delete() for that. >>> c = q.choice_set.filter(choice_text__startswith='Just hacking') >>> c.delete()