Django Simple Shipping Model The Right Way?

Question

I'm looking for suggestions on creating a Django model structure for a shipping table, can you help? I wanted to kind of simple.. This is the stuff I want to store :

        | Fedex          | UPS           | USPS
------------------------------------------------------------------
GROUND  | Home Delivery  | Ground        | Parcel Select
3DAY    | Express Saver  | 3 Day Select  | Priority or First Class
2DAY    | 2Day           | 2nd Day Air   | Priority or First Class
etc     | ..             | ..            | ..

I would like to create a Model(s) out of these, but I feel like I'm just creating a mess and my thinking is totally off. Here was my thinking, and Im not satisfied with it:

class ShippingMethod(models.Mod
    title = models.CharField(
                    max_length = 20,
                    choices = SHIPPING_TITLES, # Just a list of Fedex/UPS etc
                    default = "fedex"
                    )
    service = models.CharField(
                    max_length = 20,
                    choices = SHIPPING_SERVICES, # Just a list of Ground, 2day, etc
                    default = "GROUND"

    # This model is lacking the "Description", eg: "Parcel Select, 2nd Day Air".

I didn't want to make three model

ShippingMethod -- UPS, USPS, Fedex
ShippingType  -- Ground, 2Day
ShippingDescription -- "Parcel Select, 2nd Day Air"

I feel like I've just started over-complicated thing.. Any advice would be appreciated :)

Answer 1

I would imagine you will be stuck making three models. However, I would suggest making your ShippingMethod (UPS, USPS, FedEx) model, and your ShippingType (Ground, 2 Day, 3 Day, etc.), then the third model a ShippingMethodType model which ties the other two like:

ShippingMethodType(models.Model):
    shipping_method = ForeignKey(ShippingMethod)
    shipping_type = ForeignKey(ShippingType)

This way you can display the ShippingMethodType to select which will be a combination of the method and type and what it is called for that shipper. That's how I would do it, and I can't think of any more elegant way, other than this possibility:

from django.db import models

Shipper(models.Model)
    name = models.CharField(max_length=16)
    .
    .
    ground = models.CharField(max_length=16)
    two_day = models.CharField(max_length=16)
    three_day = models.CharField(max_length=16)
    .
    .
    def shipPackage(self):
        .
        <some default functionality for all shippers>
        .

ShipperUPS(Shipper):
    .
    <any UPS-specific fields>
    .
    .
    def shipPackage(self):
        .
        <UPS-specific functionality>
        super(Shipper, self).shipPackage()

ShipperUSPS(Shipper):
    .
    .
    <overloaded USPS methods>

ShipperFedEx(Shipper):
    .
    .
    <overloaded FedEx methods>

Something like this could come in handy, or may be overkill, depending on your specifications. But, I don't think you can get away with not using multiple models.