Clearer?

gistfile1.py

class CompanyRecordRow(Row):

    format = [
        ('id', '2s', converters.StringConverter(2)),
        ('acount_id', '10s', converters.StringConverter(10)),
        ('total_orders', '8s', converters.IntegerConverter(8)),
        ('file_version', '10s', converters.StringConverter(10)),
        ('affiliate_id', '20s', converters.StringConverter(20)),
        ('_filler', '99s', converters.BlankConverter(99)),
    ]


class OrderRecordRow(Row):

    format = [
        ('id', '2s', converters.StringConverter(2)),
        ('order_number', '22s', converters.StringConverter(22)),
        ('ingram_order_reference', '8s', converters.IntegerConverter(8)),
        ('status', '2s', converters.StringConverter(2)),
        ('_filler', '75s', converters.BlankConverter(75)),
        ('line_count', '4s', converters.IntegerConverter(4)),
        ('_filler', '2s', converters.BlankConverter(36)),
    ]


class OrderDetailRow(Row):

    format = [
        ('id', '2s', converters.StringConverter(2)),
        ('order_number', '22s', converters.StringConverter(22)),
        ('warehouse_code', '17s', converters.StringConverter(17)),
        ('line_id', '10s', converters.StringConverter(10)),
        ('_filler', '10s', converters.BlankConverter(10)),
        ('qty_requested', '5s', converters.IntegerConverter(2)),
        ('qty_predicted', '5s', converters.IntegerConverter(2)),
        ('_filler', '5s', converters.BlankConverter(5)),
        ('status', '2s', converters.StringConverter(2)),
        ('isbn_10', '15s', converters.StringConverter(15)),
        ('isbn_10_shipped', '15s', converters.StringConverter(15)),
        ('product_id', '15s', converters.StringConverter(15)),
        ('isbn_13', '15s', converters.StringConverter(15)),
        ('_filler', '11s', converters.BlankConverter(11))
    ]


class AcknowledgementFileReader(FileReader):

    rows = {
        "CR": CompanyRecordRow,
        "OR": OrderRecordRow,
        "OD": OrderDetailRow,
    }