How to populate a django manytomany database from excel file - django

Question

I'm trying to transfer data from a excel file into a manytomany table in my sqlite3 database.
model.py
from django.db import models
class Major(models.Model):
name = models.CharField(max_length=30, db_index=True)
class School(models.Model):
name = models.CharField(max_length=50, db_index=True)
majors = models.ManyToManyField(Major)
class professor(models.Model):
ProfessorIDS = models.IntegerField()
ProfessorName = models.CharField(max_length=100)
ProfessorRating = models.DecimalField(decimal_places=2,max_digits=4)
NumberofRatings = models.CharField(max_length=50)
#delete major from the model
school = models.ForeignKey(School , on_delete=models.CASCADE)
major = models.ForeignKey(Major , on_delete=models.CASCADE)
def __str__(self):
return self.ProfessorName
Populating Script
# populate.py, school_major_link
import os
import django
from django_xlspopulator.populator import Populator
os.environ.setdefault('DJANGO_SETTINGS_MODULE','blog_project.settings')
django.setup()
from locate.models import Major
pop = Populator('C:/Users/David/Desktop/db_setup/School_Majors.xlsx', school_majors)
pop.populate()
Error message when attempting to run script
Traceback (most recent call last):
File "populate_school_major.py", line 9, in <module>
pop = Populator('C:/Users/David/Desktop/db_setup/School_Majors.xlsx', school_majors)
NameError: name 'school_majors' is not defined
But it makes sense since this script looks for the class name in the models section verses the name of the table, so I'm not too sure how I would be able to populate the correct table, Note that I already have a table named majors which is already populated using this script, but since django makes manytomany relationships via a variable verses a seperate class i'm stuck.
I tried using the populating script above, but noticed that this wouldn't work since it's locating the class, verses what the database table is saved as. (In sqlite3, the tables name for the majors manytomanyfield is called school_majors).
If anyone has any recommendations on how I can populate the db that would be great.
Picture below of the database table name.
Excel file below

Answer 1

When you define a ManyToManyField in Django, it creates a model behind-the-scenes to store the mapping.
You can access this model using the through attribute of the ManyToManyField. In your case, this would be:
locate.models.School.majors.through
Your current script is failing because school_majors is not a defined name at all - try replacing it with a reference to the model you wish to populate:
pop = Populator('C:/Users/David/Desktop/db_setup/School_Majors.xlsx', locate.models.School.majors.through)
pop.populate()
If this does not work, you might wish to consider defining an explicit through model on the ManyToManyField (as explained in the Django docs) and then specify that in your Populator instantiation.
Good luck!

Answer 2

As lukewarm stated, setting the through allowed me to create a class, which I was able to reference with my script which strictly would be able to populate by locating a class in the model.py
from django.db import models
class Major(models.Model):
name = models.CharField(max_length=30, db_index=True)
class School(models.Model):
name = models.CharField(max_length=50, db_index=True)
school_Major_merge = models.ManyToManyField(Major, through='School_Major')
class School_Major(models.Model):
major = models.ForeignKey(Major, on_delete=models.CASCADE)
school = models.ForeignKey(School, on_delete=models.CASCADE)
class professor(models.Model):
ProfessorIDS = models.IntegerField()
ProfessorName = models.CharField(max_length=100)
ProfessorRating = models.DecimalField(decimal_places=2,max_digits=4)
NumberofRatings = models.CharField(max_length=50)
#delete major from the model
school = models.ForeignKey(School , on_delete=models.CASCADE)
major = models.ForeignKey(Major , on_delete=models.CASCADE)
def __str__(self):
return self.ProfessorName