admin.py

from django.contrib import admin
from django.forms.models import BaseInlineFormSet
from .models import Item, ItemLocation


@admin.register(Item)
class ItemAdmin(admin.ModelAdmin):
    fieldsets = (
        ('Item Details', {
            'fields': ('sku', 'item_name', 'item_description', 'item_search',
                       ('item_lead_time', 'item_lead_time_period'), 'reorder_point', 'is_consumable')
        }),
        ('Category & Group', {
            'fields': ('item_category', 'item_group', )
        }),
        ('Vendor & Manufacturer', {
            'fields': ('vendor', 'manufacturer')
        }),
        ('Item Pricing', {
            'fields': ('unit_price', 'unit_cost')
        }),        
    )

    inlines = [ItemLocationInline,]    
    list_display = ('sku', 'item_name', 'vendor', 'total_qty_on_hand', 'total_qty_on_order',)
    list_display_links = ('sku', 'item_name',)
    list_filter = ('item_category', 'item_group', 'vendor', 'manufacturer',)
    search_fields = ['sku', 'item_name', 'item_description', 'item_search', 'vendor']
    readonly_fields = ('id',)

    # override the save_formset method and update the total qty's for each location
    def save_formset(self, request, form, formset, change):
        instances = formset.save(commit=False)
        for instance in instances:
            instance.save()
            instance.item.update_totals()
        formset.save_m2m()

    class Meta:
        verbose_name = 'Item'
        verbose_name_plural = 'Items'
        ordering = ('-id',)