Attribute Error 'NoneType' object has no attribute '_prefetch_related_lookups'

[Warwick Lewarne]

Hi all,

I keep getting the above error and I am not sure what I need to do to correct it. An example will assist.

my model:

class Product_Group(models.Model):

    customer_id = models.ForeignKey(Customer, on_delete=models.CASCADE)

    prod_group = models.CharField(max_length=30, unique = True, verbose_name = "product group")

    

    def __str__(self):

        return self.prod_group

class Part_Number(models.Model):

    customer_id = models.ForeignKey(Customer, on_delete=models.CASCADE, related_name = 'customer')

    prod_group = models.ForeignKey(Product_Group, on_delete=models.DO_NOTHING, related_name='product')

    part_number = models.CharField(max_length=40, unique = True)

    part_description = models.CharField(max_length=60)

   

    def __str__(self):

        return self.part_description

My form:

from django import forms

from django.contrib.auth.models import User

from .models import Department, Product_Group, Part_Number, Reject_Reason, Return_Reason, Supplier, Consumer

from accounts.models import Customer_User

class Report_GenerateForm(forms.Form):

    part_number = forms.ModelChoiceField(queryset=None, label='Part Number')

    reject_data = forms.ModelChoiceField(queryset=None)

    select_data = forms.ModelChoiceField(queryset=None)

    def __init__(self, *args, **kwargs):

        customer_id = kwargs.pop('customer_id')

        table_select = kwargs.pop('table_select')

        product = kwargs.pop('product')

        super(Report_GenerateForm, self).__init__(*args, **kwargs)

        self.fields['part_number'].queryset = Part_Number.objects.filter(customer_id= customer_id, prod_group = product).select_related('prod_group')

        if table_select == 1:

            self.fields['select_data'].queryset = Department.objects.filter(customer_id=customer_id)

            self.fields['select_data'].label = 'Department'

            self.fields['reject_data'].queryset = Reject_Reason.objects.all()

            self.fields['reject_data'].label = 'Reject Reason'

        if table_select == 2:

            self.fields['select_data'].queryset = Supplier.objects.filter(customer_id=customer_id)

            self.fields['select_data'].label = 'Supplier'

            self.fields['reject_data'].queryset = Return_Reason.objects.all()

            self.fields['reject_data'].label = 'Reason for Return'

        if table_select == 3:

            self.fields['select_data'].queryset = Consumer.objects.filter(customer_id=customer_id)

            self.fields['select_data'].label = 'Customer'

            self.fields['reject_data'].queryset = Return_Reason.objects.all()

            self.fields['reject_data'].label = 'Reason for Return'