def _get_cheapest_shipping(shipping_dict):

    least = None
    leastcost = None
    for key, value in shipping_dict.items():
        current = value['cost']
        if leastcost is None or current < leastcost:
            least = key
            leastcost = current

    return least
Use the shipping_dict as returned by _get_shipping_choices
dataset/ETHPy150Open dokterbob/satchmo/satchmo/apps/payment/forms.py/_get_cheapest_shipping