Django / Models / Admin / Problem with the foreign key : __str__ returned non-string (type tuple)

Question

I have already tried multiple solutions find on other topics but nothing works.

I have a problem the foreign key in Django Admin. Impossible to see a records or add a new record.

I have a table convertion_factor with no NULL values. see postgreSQL config

This is my model :

class convertion_factor(models.Model):
    foodID = models.ForeignKey('food_name', on_delete=models.CASCADE)
    measureID = models.ForeignKey('measure_name', on_delete=models.CASCADE)
    conversionFactorValue = models.FloatField()
    convFactorDateOfEntry = models.DateField(auto_now=False, auto_now_add=False) 

In order to views the data in Django Admin, you have to add def __str__(self): to the model. Ok let's do that :

class convertion_factor(models.Model):
    foodID = models.ForeignKey('food_name', on_delete=models.CASCADE)
    measureID = models.ForeignKey('measure_name', on_delete=models.CASCADE)
    conversionFactorValue = models.FloatField()
    convFactorDateOfEntry = models.DateField(auto_now=False, auto_now_add=False) 

    def __str__(self):
        return self.conversionFactorValue

Now when I go to Django Admin and I click on the model convertion_factor I can see the table just fine but when I try to click on a record to edit it, I have this error :

TypeError at /admin/kalo/convertion_factor/19505/change/

Exception Type: TypeError at /admin/kalo/convertion_factor/19505/change/
Exception Value: __str__ returned non-string (type float)

I have the impression this is an error due to the foreign key because with my others models without a foreign key, everythings work just fine.

In the function def __str__(self): I have tried :

return self.foodID.__str__ but same error

return str(self.foodID) but same error

Do you have any idea ?

Thanks for the help.

Answer 1

def __str__(self):
        return str(self.conversionFactorValue)

This code works correctly with float value, Returns float value in the form of string value

I have added a screenshot below. django admin page view