django-okpay (or python-okpay) payment processing script. Simple version, without full support of API and tests.

django-okpay.py

class OkpayProcessor(object):
    '''OKPAY payment notification check and enrollment class.

    https://dev.okpay.com/en/manual/ipn/listener-implementation.html
    https://dev.okpay.com/en/manual/ipn/testing.html
    https://dev.okpay.com/en/guides/accepting-payments.html#ipn
    https://dev.okpay.com/en/guides/client-verification.html#code

    Usage:
        processor = MyWebsiteOkpayProcessor(request.POST, logger=transactions_logger)
        verification_success = processor.verify_ipn()

        if not verification_success:
            transactions_logger.error('Wow. Wrong data from okpay. Such suspicious. Much strange. Wow.')
            return HttpResponse('verification failed')
        else:
            processor.enroll()

    '''
    OKPAY_VERIFICATION_URL = 'https://checkout.okpay.com/ipn-verify'

    OKPAY_IPN_INVALID = b'INVALID'
    OKPAY_IPN_VERIFIED = b'VERIFIED'
    OKPAY_IPN_TEST = b'TEST'

    OKPAY_STATUS_COMPLETED = 'completed'

    # to check it every time something database-modifying called
    __verification_result = False

    def __init__(self, request_data, logger):
        if 'ok_verify' in request_data:
            raise Exception("ok_verify must not be present in initial request data for {}".format(
                self.__class__.__name__
            ))
        self._request_data = request_data
        self.logger = logger
        return

    def allow_test_requests(self):
        return settings.DEBUG

    def verify_ipn(self):
        self.__verification_result = False
        headers = {
            'Content-Type': 'application/x-www-form-urlencoded',
        }
        verify_request_payload = {
            'ok_verify': 'true',
        }
        verify_request_payload.update(self._request_data)

        resp = requests.post(self.OKPAY_VERIFICATION_URL, data=verify_request_payload, headers=headers)
        msg = 'resp is {} for verification of request {}'.format(
            resp.content, verify_request_payload
        )
        self.logger.info(msg)

        # if resp.content == self.OKPAY_IPN_VERIFIED or (resp.content == self.OKPAY_IPN_TEST and self.allow_test_requests()):  # NOQA
        # if resp.content == self.OKPAY_IPN_VERIFIED or resp.content == self.OKPAY_IPN_TEST:
        if resp.content == self.OKPAY_IPN_VERIFIED:  # anyway disable test on production.
            self.__verification_result = True
        return self.__verification_result

    def enroll(self):
        if not self.__verification_result:
            raise Exception("Trying to enroll while verifications is failed or ommited!")
        # check status: https://dev.okpay.com/en/manual/ipn/variables.html#ok_txn_status
        if self._request_data['ok_txn_status'] != self.OKPAY_STATUS_COMPLETED:
            self.logger.error("Status {} != completed".format(self._request_data['ok_txn_status']))
            return False
        if self._request_data['ok_txn_currency'] != "USD":
            # Remove it if you need to.
            self.logger.error("Currency {} != USD".format(self._request_data['ok_txn_currency']))
            return False
        return self._do_enroll()

    @transaction.atomic
    def _do_enroll(self):
        # here you can do whatever you want with self._request_data, it's validated.
        # don't forget to check ok_ipn_test, don't forget about multiple fields with money amount (gross, tax, etc),
        # and about ok_txn_status - now everything except completed is ignored, but you may implement refund/freeze/etc.
        raise NotImplementedError('Please subclass OkpayProcessor and implement _do_enroll')