def process_pdt(request):
    """
    Payment data transfer implementation:
    https://developer.paypal.com/webapps/developer/docs/classic/products/payment-data-transfer/

    This function returns a tuple of (pdt_obj, failed)
    pdt_obj is an object of type PayPalPDT
    failed is a flag that is True if the input data didn't pass basic validation.

    Note: even for failed=False You must still check the pdt_obj is not flagged i.e.
    pdt_obj.flag == False
    """

    pdt_obj = None
    txn_id = request.GET.get('tx')
    failed = False
    if txn_id is not None:
        # If an existing transaction with the id tx exists: use it
        try:
            pdt_obj = PayPalPDT.objects.get(txn_id=txn_id)
        except PayPalPDT.DoesNotExist:
            # This is a new transaction so we continue processing PDT request
            pass

        if pdt_obj is None:
            form = PayPalPDTForm(request.GET)
            if form.is_valid():
                try:
                    pdt_obj = form.save(commit=False)
                except Exception as e:
                    warn_untested()
                    error = repr(e)
                    failed = True
            else:
                warn_untested()
                error = form.errors
                failed = True

            if failed:
                warn_untested()
                pdt_obj = PayPalPDT()
                pdt_obj.set_flag("Invalid form. %s" % error)

            pdt_obj.initialize(request)

            if not failed:
                # The PDT object gets saved during verify
                pdt_obj.verify()
    else:
        pass  # we ignore any PDT requests that don't have a transaction id

    return (pdt_obj, failed)
Payment data transfer implementation:
    https://developer.paypal.com/webapps/developer/docs/classic/products/payment-data-transfer/

    This function returns a tuple of (pdt_obj, failed)
    pdt_obj is an object of type PayPalPDT
    failed is a flag that is True if the input data didn't pass basic validation.

    Note: even for failed=False You must still check the pdt_obj is not flagged i.e.
    pdt_obj.flag == False