Python 3.x 如何将实例传递给视图？

我无法理解系统正在恢复的抱怨。 这是系统的视图

 def AddMarksView(request):
        class_name = request.session.get('class_name')
        subject = Subject.objects.filter(name='Maths')
        exam = Exam.objects.filter(name='Endterm')
        students =  Students.objects.filter(school=request.user.school,klass__name = class_name,stream__name='South')
        if request.method == 'POST':
            for student in students:
                marks = int(request.POST['marks'])
                marks_object = Marks.objects.create(student=student,marks=marks,subject=subject,exam=exam)
        else:
            return render(request,'feed_marks.html')
        return redirect('search_m')

返回的错误是

Cannot assign "<QuerySet [<Exam: Endterm>]>": "Marks.exam" must be a "Exam" instance.

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如何格式化视图以使其不返回错误？

请尝试获取而不是筛选，以便代码读取

def AddMarksView(request):
        class_name = request.session.get('class_name')
        subject = Subject.objects.get(name='Maths')
        exam = Exam.objects.get(name='Endterm')
        students =  Students.objects.filter(school=request.user.school,klass__name = class_name,stream__name='South')
        if request.method == 'POST':
            for student in students:
                marks = int(request.POST['marks'])
                marks_object = Marks.objects.create(student=student,marks=marks,subject=subject,exam=exam)
        else:
            return render(request,'feed_marks.html')
        return redirect('search_m')

---

非常感谢@Ptar。它是那样工作的。。。

def AddMarksView(request):
        class_name = request.session.get('class_name')
        subject = Subject.objects.get(name='Maths')
        exam = Exam.objects.get(name='Endterm')
        students =  Students.objects.filter(school=request.user.school,klass__name = class_name,stream__name='South')
        if request.method == 'POST':
            for student in students:
                marks = int(request.POST['marks'])
                marks_object = Marks.objects.create(student=student,marks=marks,subject=subject,exam=exam)
        else:
            return render(request,'feed_marks.html')
        return redirect('search_m')