parameters: (self, amount, currency, return_url, cancel_url, **kwargs)
return_statement: return False
docstring: To set up an Express Checkout transaction, you must invoke the SetExpressCheckout API
          to provide sufficient information to initiate the payment flow and redirect to PayPal if the
          operation was successful.
  
          @currency: Look at 'https://cms.paypal.com/us/cgi-bin/?cmd=_render-content&content_ID=developer/e_howto_api_nvp_currency_codes'
          @amount : should be string with the following format '10.00'
          @return_url : should be in the format scheme://hostname[:uri (optional)]
          @cancel_url : should be in the format scheme://hostname[:uri (optional)]
  
          @returns bool
  
          If you want to add extra parameters, you can define them in **kwargs dict. For instance:
           - SetExpressCheckout(10.00, US, http://www.test.com/cancel/, http://www.test.com/return/, **{'SHIPTOSTREET': 'T Street', 'SHIPTOSTATE': 'T State'})
docstring_summary: To set up an Express Checkout transaction, you must invoke the SetExpressCheckout API
          to provide sufficient information to initiate the payment flow and redirect to PayPal if the
          operation was successful.
docstring_tokens: To set up an Express Checkout transaction you must invoke the SetExpressCheckout API to provide sufficient information to initiate the payment flow and redirect to PayPal if the operation was successful .
function: def SetExpressCheckout(self, amount, currency, return_url, cancel_url, **kwargs):
          """
          To set up an Express Checkout transaction, you must invoke the SetExpressCheckout API
          to provide sufficient information to initiate the payment flow and redirect to PayPal if the
          operation was successful.
  
          @currency: Look at 'https://cms.paypal.com/us/cgi-bin/?cmd=_render-content&content_ID=developer/e_howto_api_nvp_currency_codes'
          @amount : should be string with the following format '10.00'
          @return_url : should be in the format scheme://hostname[:uri (optional)]
          @cancel_url : should be in the format scheme://hostname[:uri (optional)]
  
          @returns bool
  
          If you want to add extra parameters, you can define them in **kwargs dict. For instance:
           - SetExpressCheckout(10.00, US, http://www.test.com/cancel/, http://www.test.com/return/, **{'SHIPTOSTREET': 'T Street', 'SHIPTOSTATE': 'T State'})
          """
          parameters = {
              'METHOD' : 'SetExpressCheckout',
              'NOSHIPPING' : 1,
              'PAYMENTACTION' : 'Sale',
              'RETURNURL' : return_url,
              'CANCELURL' : cancel_url,
              'AMT' : amount,
              'CURRENCYCODE' : currency,
          }
          
          parameters.update(kwargs)
          query_string = self.signature + urllib.urlencode(parameters)
          response = urllib.urlopen(self.NVP_API_ENDPOINT, query_string).read()
          response_dict = parse_qs(response)
          self.api_response = response_dict
          state = self._get_value_from_qs(response_dict, "ACK")
          if state in ["Success", "SuccessWithWarning"]:
              self.token = self._get_value_from_qs(response_dict, "TOKEN")
              return True
  
          self.setexpresscheckouterror = GENERIC_PAYPAL_ERROR
          self.apierror = self._get_value_from_qs(response_dict, "L_LONGMESSAGE0")
          return False
function_tokens: def SetExpressCheckout ( self , amount , currency , return_url , cancel_url , * * kwargs ) : parameters = { 'METHOD' : 'SetExpressCheckout' , 'NOSHIPPING' : 1 , 'PAYMENTACTION' : 'Sale' , 'RETURNURL' : return_url , 'CANCELURL' : cancel_url , 'AMT' : amount , 'CURRENCYCODE' : currency , } parameters . update ( kwargs ) query_string = self . signature + urllib . urlencode ( parameters ) response = urllib . urlopen ( self . NVP_API_ENDPOINT , query_string ) . read ( ) response_dict = parse_qs ( response ) self . api_response = response_dict state = self . _get_value_from_qs ( response_dict , "ACK" ) if state in [ "Success" , "SuccessWithWarning" ] : self . token = self . _get_value_from_qs ( response_dict , "TOKEN" ) return True self . setexpresscheckouterror = GENERIC_PAYPAL_ERROR self . apierror = self . _get_value_from_qs ( response_dict , "L_LONGMESSAGE0" ) return False