在 django 中使用 distinct 方法时如何使用过滤数据？

Question

请帮助我解决我的问题我希望我的标题足以理解我的意思，请帮助我解决这个问题。

当我尝试这个时：

id_list = grade.objects.filter(Teacher=m.id).values_list('Students_Enrollment_Records_id',flat=True).distinct()

我使用distinct()从查询结果中消除重复的学生注册记录行，但我想知道为什么结果是这样的：

我应该怎么做才能在我的 html 中显示学生名称而不是 QuerySet？

这是我目前的views.py：

id_list = grade.objects.filter(Teacher=m.id).values_list('Students_Enrollment_Records_id',flat=True).distinct()
print(id_list)
grades = grade.objects.filter(Students_Enrollment_Records_id__in=id_list)
print(grades)

这是我的 models.py：

class grade(models.Model):
    Teacher = models.ForeignKey(EmployeeUser, related_name='+', on_delete=models.CASCADE,
                                null=True, blank=True)
    Grading_Categories = models.ForeignKey(gradingCategories, related_name='+', on_delete=models.CASCADE,
                                           null=True, blank=True)
    Subjects = models.ForeignKey(Subject, related_name='+', on_delete=models.CASCADE, null=True)
    Students_Enrollment_Records = models.ForeignKey(StudentsEnrolledSubject, related_name='+',
                                                    on_delete=models.CASCADE, null=True)
    Average = models.FloatField(null=True, blank=True)

更新

当我尝试这个时

piste = grade.objects.filter(Teacher_id=m.id).values_list('Students_Enrollment_Records').annotate(Average=Avg('Average')).order_by('Grading_Categories').distinct()

计算是固定的，但没有显示教师姓名，学科和学生姓名，但显示ID是这样的

这是我想要的答案

这就是我在 html 中发布的方式

views.py

return render(request, 'Homepage/index.html', {"piste":piste})

html

{% for n in piste %}
          <tr>
              <td>{{n.Teacher}}</td>
              <td>{{n.Subjects}}</td>
              <td>{{n.Students_Enrollment_Records.Students_Enrollment_Records.Student_Users}}</td>
              <td>{{n}}</td>
          </tr>
          {% endfor %}

这是model.py

class EmployeeUser(models.Model):
    Image = models.ImageField(upload_to='images', null=True, blank=True)
    Employee_Number = models.CharField(max_length=500, null=True)
    Username = models.CharField(max_length=500, null=True)
    Password = models.CharField(max_length=500, null=True)
    My_Department = models.ForeignKey(Department, related_name='+', on_delete=models.CASCADE, blank=True)
    My_Position = models.ForeignKey(Position, related_name='+', on_delete=models.CASCADE, blank=True)
    Firstname = models.CharField(max_length=500, null=True)
    Middle_Initial = models.CharField(max_length=500, null=True)
    Lastname = models.CharField(max_length=500, null=True)
    Educational_Attainment = models.ForeignKey(EducationalAttainment, related_name='+', on_delete=models.CASCADE,
                                               null=True)
    Landline = models.CharField(max_length=500, null=True)
    Mobile_Number = models.CharField(max_length=500, null=True)
    Email = models.CharField(max_length=500, null=True)
    Facebook_Acoount = models.CharField(max_length=500, null=True)

    Fathers_Firstname = models.CharField(max_length=500, null=True)
    Fathers_Middle_Initial = models.CharField(max_length=500, null=True)
    Fathers_Lastname = models.CharField(max_length=500, )
    Educational_Attainment_Father = models.ForeignKey(EducationalAttainment, related_name='+', on_delete=models.CASCADE,
                                                      null=True)
    Father_Occupation = models.CharField(max_length=500, null=True)
    Father_Company_Employed = models.CharField(max_length=500, null=True)
    Father_Landline = models.CharField(max_length=500, null=True)
    Father_MobileNo = models.CharField(max_length=500, null=True)
    Father_Email = models.CharField(max_length=500, null=True)
    Father_Facebook_Account = models.CharField(max_length=500, null=True)

    Mother_FirstName = models.CharField(max_length=500, null=True)
    Mother_Middle_Initial = models.CharField(max_length=500, null=True)
    Mother_Maiden_LastName = models.CharField(max_length=500, null=True)
    Educational_AttainmentID_Mother = models.ForeignKey(EducationalAttainment, related_name='+',
                                                        on_delete=models.CASCADE, null=True)
    Mother_Occupation = models.CharField(max_length=500, null=True)
    Mother_Company_Employed = models.CharField(max_length=500, null=True)
    Mother_Landline = models.CharField(max_length=500, null=True)
    Mother_MobileNo = models.CharField(max_length=500, null=True)
    Mother_Email = models.CharField(max_length=500, null=True)
    Mother_Facebook_Account = models.CharField(max_length=500, null=True)
    Family_Status = models.ForeignKey(FamilyStatu, related_name='+', on_delete=models.CASCADE, null=True)
    Country = models.CharField(max_length=500, null=True)
    ZIP_Postal_Code = models.CharField(max_length=500, null=True)
    State_Province = models.CharField(max_length=500, null=True)
    City = models.CharField(max_length=500, null=True)
    Barangay = models.CharField(max_length=500, null=True)
    Unit_Number_Street = models.CharField(max_length=500, null=True)
    LandMark = models.CharField(max_length=500, null=True)
    AddressLine1 = models.CharField(max_length=500, null=True)
    AddressLine2 = models.CharField(max_length=500, null=True)
    AddressLine3 = models.CharField(max_length=500, null=True)

    def __str__(self):
        suser = '{0.Firstname}   {0.Middle_Initial}      {0.Lastname}'
        return suser.format(self)

class StudentsEnrolledSubject(models.Model):
    Students_Enrollment_Records = models.ForeignKey(StudentsEnrollmentRecord, related_name='+',
                                                    on_delete=models.CASCADE, null=True)
    Subject_Section_Teacher = models.ForeignKey(SubjectSectionTeacher, related_name='+', on_delete=models.CASCADE,
                                                null=True)

这是完整的视图.py

m = EmployeeUser.objects.get(Username=request.POST['p_user'], Password = request.POST['p_pass'], My_Position =request.POST['position'])
piste = grade.objects.all().filter(Teacher=m.id).values_list('Students_Enrollment_Records').annotate(Average=Avg('Average')).order_by('Grading_Categories').distinct()
return render(request, 'Homepage/index.html', {"piste":piste})

更新

当我尝试@nigel222 先生的这个答案时

piste = grade.objects.filter(Teacher=m.id).annotate(grade_average=Avg('Average')).order_by('Grading_Categories').distinct()

到我的html

{% for n in piste %}
      <tr>
          <td>{{n.Teacher}}</td> <!-- 1 -->
          <td>{{n.Subjects}}</td> <!-- 2 -->
          <td>{{n.Students_Enrollment_Records.Students_Enrollment_Records.Student_Users}}
               </td>  <!-- 3 -->
          <td>{{n}}</td>  <!--4 -->
      </tr>
      {% endfor %}

我得到了这个结果

Answer 1

我已经有几年没有和 Django 一起工作了，但这就是我认为正在发生的事情。

您正在将 values_list（一个元组）分配给 piste。您没有将 grade 对象分配给 piste。但是，在您的模板中，您希望 piste 的元素是成绩。

我认为您需要先获取grade 对象并将其发送到模板以及piste。

Answer 2

您不想要values_list（这是您在第 4 列中获得的数据）。你想要一个 grade 对象的查询集：

piste = grade.objects.filter(Teacher_id=m.id
        ).annotate(Average=Avg('Average')
        ).order_by('Grading_Categories'
        ).distinct()

然后在你的模板中，类似

{% for n in piste %}
      <tr>
          <td>{{n.Teacher}}</td> <!-- 1 -->
          <td>{{n.Subjects}}</td> <!-- 2 -->
          <td>{{n.Students_Enrollment_Records.Students_Enrollment_Records.Student_Users}}
               </td>  <!-- 3 -->
          <td>{{n}}</td>  <!--4 -->
      </tr>
      {% endfor %}

1 和 2 渲染 EmployeeUser 和 Subject 对象。 1 将返回EmployeeUser 的__str__ 表示，这应该没问题。或者，您可以在模板中明确使用 {{n.Teacher.FirstName}} 等。

3 我不明白，因为您没有显示 Students_Enrolled_Subject 模型。

4 现在是错误的。也许你想要注解{{n.Average}}？

请尽快学习使用 Django/Python 编码约定。 Model 子类（以及一般的 Python 类名）以大写字母开头。类的实例是小写的。字段名/属性通常是小写字母，并且绝对以小写字母开头。模型子类名称是单数名称而不是复数名称。不这样做对于任何有经验的 Django 编码器来说都是非常混乱的。所以，

class Grade(models.Model):
    teacher = models.ForeignKey(EmployeeUser, related_name='+', on_delete=models.CASCADE,
                            null=True, blank=True)
    grading_categories = models.ForeignKey(GradingCategory, related_name='+', on_delete=models.CASCADE,
                                       null=True, blank=True)
    subject = models.ForeignKey(Subject, related_name='+', on_delete=models.CASCADE, null=True)
    students_enrollment_records = models.ForeignKey(StudentsEnrolledSubject, related_name='+',
                                                on_delete=models.CASCADE, null=True)

Answer 3

这是我能为你做的最好的。我认为您应该根据学生来选择并过滤给老师的成绩。我还对所有主题进行了预取，因为我不太清楚你需要在那里做什么。

students = Student.objects.filter(
    grades__teacher_id=teacher.id,
).annotate(
    total_avg=Avg('grades__Average')
).prefetch_related('grades__Subjects')

模板：

{% for student in students %}
      <tr>
          <td>{{teacher}}</td>
          <td>{{student.grades.subjects.all}}</td>
          <td>{{student}}</td>
          <td>{{student.total_avg}}</td>
      </tr>
{% endfor %}