| python manage.py shell
 
 >>> 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.save()
 >>> q.id
 1
 >>> q.question_text
 "What's new?"
 >>> q.pub_date
 datetime.datetime(2022, 7, 12, 14, 17, 48, 894694, tzinfo=datetime.timezone.utc)
 
 >>> q.question_text = "What' up?"
 >>> q.save()
 
 >>> Question.objects.all()
 <QuerySet [<Question: Question object (1)>]>
 >>> Question.objects.get(pub_date__year=current_year)
 <Question: What's up?>
 >>> Question.objects.get(pk=1) # pk 主键缩写
 <Question: What's up?>
 
 
 
 >>> q.choice_set.all()
 <QuerySet []>
 >>> 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)
 >>> c.question
 <Question: What' up?>
 >>> q.choice_set.all()
 <QuerySet [<Choice: Not much>, <Choice: The sky>, <Choice: Just hacking again>]>
 >>> q.choice_set.count()
 3
 # 删
 >>> c = q.choice_set.filter(choice_text__startswith='Just hacking')
 >>> c.delete()
 # Use double underscores to separate relationships.
 >>> Choice.objects.filter(question__pub_date__year=current_year)
 <QuerySet [<Choice: Not much>, <Choice: The sky>]>
 
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