I'm trying to perform math operation (specifically addition) with the contents of integer field-CodePudding

I'm trying to perform math operation (specifically addition) with the values of integer fields on my django models but i kept getting this warning even before running the program: "Class 'IntegerField' does not define 'add', so the ' ' operator cannot be used on its instances"

this is my django model code:

class Applicants(models.Model):
    fname = models.CharField(max_length=255)
    lname = models.CharField(max_length=255)
    number = models.CharField(max_length=255)
    email = models.CharField(max_length=255)
    gender = models.CharField(max_length=255)
    p_course = models.CharField(max_length=255)
    o_course = models.CharField(max_length=255)
    grade1 = models.IntegerField(max_length=255)
    grade2 = models.IntegerField(max_length=255)
    grade3 = models.IntegerField(max_length=255)
    grade4 = models.IntegerField(max_length=255)
    grade5 = models.IntegerField(max_length=255)
    grade6 = models.IntegerField(max_length=255)
    total_grade = grade1   grade2   grade3   grade4   grade4   grade5

CodePudding user response：

class Applicants(models.Model):
    fname = models.CharField(max_length=255)
    lname = models.CharField(max_length=255)
    number = models.CharField(max_length=255)
    email = models.CharField(max_length=255)
    gender = models.CharField(max_length=255)
    p_course = models.CharField(max_length=255)
    o_course = models.CharField(max_length=255)
    grade1 = models.IntegerField()
    grade2 = models.IntegerField()
    grade3 = models.IntegerField()
    grade4 = models.IntegerField()
    grade5 = models.IntegerField()
    grade6 = models.IntegerField()
    
    @property
    def get_sum_of_grades(self):
    total_grade = self.grade1   self.grade2   self.grade3   self.grade4   self.grade4   self.grade5
        return total_grade

CodePudding user response：

Model.clean()¶

This method should be used to provide custom model validation, and to modify attributes on your model if desired. For instance, you could use it to automatically provide a value for a field, or to do validation that requires access to more than a single field (source)

As described here, you should implement a clean method to your model:

class Applicants(models.Model):
    fname = models.CharField(max_length=255)
    lname = models.CharField(max_length=255)
    number = models.CharField(max_length=255)
    email = models.CharField(max_length=255)
    gender = models.CharField(max_length=255)
    p_course = models.CharField(max_length=255)
    o_course = models.CharField(max_length=255)
    grade1 = models.IntegerField()
    grade2 = models.IntegerField()
    grade3 = models.IntegerField()  # btw Integerfields don't have `max_lenght`
    grade4 = models.IntegerField()
    grade5 = models.IntegerField()
    grade6 = models.IntegerField()
    total_grade = models.IntegerField()

    def clean(self):
        super().clean()
        self.total_grade = sum(self.grade1, self.grade2, self.grade3, self.grade4, self.grade4, self.grade5)

For sure that total_grade field will be shown in a form if you choose to use a models.ModelForm but you can go for exclude = ['total_grade'] to hide it. Be careful, the result of the computation does not reach "normal" form validation, as it runs before within the statement super().clean()