Modify database in django - django

Question

I am a beginner in django. Following is my Attendance Management App.
This is my models.py.
from django.db import models
class Subject(models.Model):
subject_name = models.CharField(max_length=20)
#attendance = models.ForeignKey(Attendance, on_delete =
models.DO_NOTHING)
attendance = models.IntegerField(default=0)
def __str__(self):
return self.subject_name
class Section(models.Model):
section_name = models.CharField(max_length=20)
subject = models.ManyToManyField(Subject)
def __str__(self):
return self.section_name
class Student(models.Model):
rollno = models.IntegerField()
name = models.CharField(max_length=20)
section = models.ForeignKey(Section, on_delete = models.DO_NOTHING,
default=0)
def __str__(self):
return str(self.rollno) + self.name
class Teacher(models.Model):
#teacher_name = models.CharField(max_length=20)
section = models.ForeignKey(Section, on_delete=models.CASCADE)
subject = models.ForeignKey(Subject, on_delete=models.CASCADE)
#section_name = models.CharField(max_length=10)
#subject_name = models.CharField(max_length=30)
def __str__(self):
return self.section.section_name+' '+self.subject.subject_name
class TeacherList(models.Model):
teacher_name = models.CharField(max_length=20)
teacher = models.ManyToManyField(Teacher)
def __str__(self):
return self.teacher_name
The line below is not working in views.py
student = models.Student.objects.get(rollno = sroll)
student.section.subject.get(subject_name = 'java').attendance += 1
student.save()
This view is called from a template when a button is clicked to add attendance of a student.
The attendance in above code is not modified. Please help me out.

Answer 1

You're saving the student, instead of the subject.
student = models.Student.objects.get(rollno = sroll)
subject = student.section.subject.get(subject_name='java')
subject.attendance += 1
subject.save()
Or, better, do the update directly in one go:
student.section.subject.filter(subject_name='java').update(attendance=F('attendance')+1)
and there's no need to save at all.