requestUrl = "https://hosted.datascopeapi.reuters.com/RestApi/v1/Authentication/RequestToken"
  
  requestHeaders={
      "X-Direct-Download": "true",
      "Prefer":"respond-async",
      "Content-Type":"application/json"
      
      }
  
  requestBody={
      "Credentials": {
      "Username": xxx,
      "Password": "xxx"
    }
  }
  
  r1 = requests.post(requestUrl, json=requestBody,headers=requestHeaders)
  
  if r1.status_code == 200 :
      jsonResponse = json.loads(r1.text.encode('ascii', 'ignore'))
      token = jsonResponse["value"]
      print ('Authentication token (valid 24 hours):')
      print (token)
  else:
      print ('Replace myUserName and myPassword with valid credentials, then repeat the request')
  
  #Step 2: send an on demand extraction request using the received token 
  requestUrl='https://hosted.datascopeapi.reuters.com/RestApi/v1/Extractions/ExtractRaw'
  
  requestHeaders={
      "X-Direct-Download": "true",
      "Prefer":"respond-async",
      "Content-Type":"application/json",
      "Authorization": "token " + token
  }
    
  requestBody={
    "ExtractionRequest": {
      "@odata.type": "#ThomsonReuters.Dss.Api.Extractions.ExtractionRequests.TickHistoryRawExtractionRequest",
      "IdentifierList": {
        "@odata.type": "#ThomsonReuters.Dss.Api.Extractions.ExtractionRequests.InstrumentIdentifierList",
        "InstrumentIdentifiers": generateChainRICs(sd,nc,bt,dTable),
                    "ValidationOptions": {
                  "AllowHistoricalInstruments": "true"
              }
      },
      "Condition": {
        "MessageTimeStampIn": "LocalExchangeTime",         #To be linked to Instrument's time zone - a mapping table needed
        #"ApplyCorrectionsAndCancellations": "false",
        "ReportDateRangeType": "Range",
        "QueryStartDate": sd+openString,  #"T18:00:00.000Z",    #To be user defined - linked to variables
        "QueryEndDate": ed+closeString,     #"T17:00:00.000Z",    #To be user defined - linked to variables
        "ExtractBy": "Ric",
        "SortBy": "SingleByRic",
        "DomainCode": "MarketPrice",
        "Fids" : fi, # "70",
        "DateRangeTimeZone" : "UTC", 
        "DisplaySourceRIC": "true"
      }
    }
  }
  
  r2 = requests.post(requestUrl, json=requestBody,headers=requestHeaders)
   
  #Step 3: poll the status of the request using the received location URL.
  #Once the request has completed, retrieve the jobId and extraction notes.
  
  requestUrl = r2.headers["location"]
    
  requestHeaders={
      "X-Direct-Download": "true",
      "Prefer":"respond-async",
      "Content-Type":"application/json",
      "Authorization":"token " + token
  }
  
  r3 = requests.get(requestUrl,headers=requestHeaders)
  
  while (r3.status_code == 202):
      print ('As we received a 202, we wait 900 seconds, then poll again (until we receive a 200)')
      time.sleep(900)
      r3 = requests.get(requestUrl,headers=requestHeaders)
  
  if r3.status_code == 200 :
      r3Json = json.loads(r3.text.encode('ascii', 'ignore'))
      jobId = r3Json["JobId"]
  
  if r3.status_code != 200 :
      print ('An error occured. Try to run this cell again. If it fails, re-run the previous cell.\n')
   
  #Step 5: get the extraction results, using the received jobId.
  #We also save the compressed data to disk, as a GZIP.
  #We only display a few lines of the data.
  
  #IMPORTANT NOTE:
  #This code is much better than that of step 4; it should not fail even with large data sets.
  #If you need to manipulate the data, read and decompress the file, instead of decompressing
  #data from the server on the fly.
  #This is the recommended way to proceed, to avoid data loss issues.
  #For more information, see the related document:
  #   Advisory: avoid incomplete output - decompress then download
  
  requestUrl = "https://hosted.datascopeapi.reuters.com/RestApi/v1/Extractions/RawExtractionResults" + "('" + jobId + "')" + "/$value"
  print "Job ID"
  print jobId
  #AWS requires an additional header: X-Direct-Download
  if useAws:
      requestHeaders={
          "Prefer":"respond-async",
          "Content-Type":"text/plain",
          "Accept-Encoding":"gzip",
          "X-Direct-Download":"true",
          "Authorization": "token " + token,
          'User-Agent':'Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/36.0.1985.143 Safari/537.36',
          "X-Client-Session-Id":"Direct AWS"
      }
  else:
      requestHeaders={
          "Prefer":"respond-async",
          "Content-Type":"text/plain",
          "Accept-Encoding":"gzip",
          "Authorization": "token " + token,
          'User-Agent':'Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/36.0.1985.143 Safari/537.36',
          "X-Client-Session-Id":"From DSS"
      }
  
  #import pdb;pdb.set_trace()
  r5 = requests.get(requestUrl,headers=requestHeaders,stream=True)
  time.sleep(3)
  #Ensure we do not automatically decompress the data on the fly:
  r5.raw.decode_content = False
  if useAws:
      print ('Content response headers (AWS server): type: ' + r5.headers["Content-Type"] + '\n')
      #AWS does not set header Content-Encoding="gzip".
  else:
      print ('Content response headers (TRTH server): type: ' + r5.headers["Content-Type"] + ' - encoding: ' + r5.headers["Content-Encoding"] + '\n')