eParcel CSV generator

def generate_csv(orders):
    """
    Generate a consignment CSV from a list of orders

    Parameters:
      orders - The list of orders to work with

    Returns:
    An iterable that contains every (\\n terminated) line of the CSV as a string.
    """
    for order in orders:
        # Each order from Shopify needs a Consignment line, and one or more
        # Article line per physical parcel being sent.  Goods being sent
        # overseas need one Goods line per Article line to pass customs.
        # Additionally, overseas consignments can only have one
        # article/physical parcel.  To simplify things, we simply print one
        # consignment, article and goods line per order. This will work in
        # all instances.
        #
        # See `docs/eParcel Consignment Import Guide.pdf`, page 8 for more
        # information

        dest = order.shipping_address

        # International consignments have different requirements
        international = dest.country_code != settings.COUNTRY_CODE

        weight_in_grams = int(order.total_weight) or settings.EPARCEL_DEFAULT_WEIGHT
        weight = "%0.2f" % (weight_in_grams / 1000.0)
        price = "%0.2f" % float(order.total_price)
        item_count = sum([int(i.quantity) for i in order.line_items])

        data = [
            ( # Consignment line
                'C',
                # B-D
                '', # Must be left blank
                settings.EPARCEL_ACCOUNT_NUMBER, # Optional, may be blank
                settings.EPARCEL_CHARGE_CODE['international' if international else 'domestic'],

                # E-F: Create a new consignee
                '',
                dest.name,

                # G-O: Shipping address
                dest.company or '',
                dest.address1 or '',
                dest.address2 or '',
                '', # address line 3
                '', # address line 4
                dest.city,
                dest.province_code,
                dest.zip,
                dest.country_code,

                # P: Required for international consignments
                # TODO This is terrible
                dest.phone or '555 1234',

                # Q-S: Display phone; fax number; special instructions
                '',
                '',
                '',

                'N', # T: No signature required
                '',  # U: Part delivery
                '',  # V: No comments
                'N', # W: Do not add consignee to address book
            ),

            ( # Article line
                'A',

                weight,      # B: Weight of this article (sum of all weights)
                '', '', '',  # C-E: Length; width; height;
                item_count,  # F: Number of articles

                'Clothing',  # G: Article description. What should go here?

                'N',         # H: Goods are NOT dangerous

                'N', '', '', # I-K: Insurance is not required
            ),
        ]
        if international:
            data.append(( # Goods line
                'G',

                # B: Shipping from this country
                settings.COUNTRY_CODE,
                # C: HS Tarrif code. Dunno what this is?
                '',
                # D: Description
                'Clothing',

                '', # E: Product type
                settings.EPARCEL_PRODUCT_CLASSIFICATION, # F

                # G-H: Quantity and weight
                item_count, weight,
                # I-J: Unit value; total value.
                price, price,
            ))

        # We can not out put this as `tablib.Dataset(*row).csv` as the
        # documentation recommends, as each row has a different length, and
        # tablib throws an error because of this. Outputting each row one by
        # results in the same output, without a giant load of extra columns on
        # some rows
        for row in data:
            yield tablib.Dataset(row).csv