How save specific user instance into database using django views

I created models called Interview, Users, Interview_interviewer like wise... Interview_interviewer table has foreign keys from other models. I just want to save data from both 2 tables to Interview_interviewer(Without django forms) table which is many to many table. So I just created the views and template for it. When button clicks it save the Interviewers to table along side with the interview. But when do it, It gave me and error called "User matching query does not exist". /home/govinda/DMG/test3/myapp/views.py in hod_inter_interviewer_2 usr = User.objects.get(id=pid) What should I do?

class Interview(models.Model):

Time = models.TimeField()
Date = models.DateField()
Venue = models.ForeignKey('Venue')
HOD = models.ForeignKey(User)
Vacancy = models.ForeignKey('Vacancy', on_delete=models.CASCADE)
Department = models.ForeignKey(Department, on_delete=models.CASCADE)
InterviewType = models.ForeignKey(InterviewType, on_delete=models.CASCADE)
Interviewer_Review = models.TextField(blank=True, null=True)
HOD_Review = models.TextField(blank=True, null=True)
HR_Review = models.TextField(blank=True, null=True)
NoOfPasses = models.PositiveIntegerField(blank=True, null=True)
NoOfFails = models.PositiveIntegerField(blank=True, null=True)
NoOfOnHolds = models.PositiveIntegerField(blank=True, null=True)
InterviewNo = models.IntegerField(blank=True, null=True)
Post = models.ForeignKey(Post, on_delete=models.CASCADE)

and

class Users(models.Model):

User = models.OneToOneField(User)
FullName = models.CharField(max_length=100)
Post = models.ForeignKey(Post)
UPhoto = models.FileField(upload_to=User_directory_path,null = True,blank=True)
Department = models.ForeignKey(Department)
UserRole = models.ForeignKey(UserRole)

def __str__(self):
    return u'{}'.format(self.User)

and

class Interview_Interviewer(models.Model):

Interview = models.ForeignKey(Interview)
Interviewer = models.ForeignKey(User)

def __str__(self):
    return u'{}'.format(self.Interviewer)

views are...

def hod_pre_interviwer_list(request, iid):

inter = Interview.objects.get(id=iid)
a = UserRole.objects.get(Role="Interviewer")
viewer = Users.objects.filter(UserRole=a.id)
return render(request, 'hod_inter_create_2.html', {'viewer': viewer, 'inter': inter, 'a':a})

def hod_inter_interviewer_2(request, iid, pid):

inter = Interview.objects.get(id=iid)
usr = User.objects.get(id=pid)
a = UserRole.objects.get(Role="Interviewer")
viewer = Users.objects.filter(UserRole=a.id)
usr_id = Users.objects.get(User=a.id)
inter_id = inter
person_id = usr_id
form = Interview_Interviewer(Interview=inter_id, Interviewer=person_id)
form.save()
return render(request, 'hod_inter_create_2.html', {'viewer': viewer, 'inter': inter})

urls are...

urlpatterns = [

url(r'^hod/hod_vacancy/test/part2/inter_list/(\d+)/$', hod_pre_interviwer_list, name="inter1"),
url(r'^hod/hod_vacancy/test/part2/inter_list/(\d+)/(\d+)/$', hod_inter_interviewer_2, name="inter2"),

]

template is...

    <a type="submit" class="btn btn-primary" href="/hod/hod_vacancy/test/part2/inter_list/{{ inter.id }}/{{ viewer.id }}">Add</a>