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  • IronPython Script to access data from Web Service using HttpWebRequest and parse returned JSON with JavaScriptSerializer


    In Spotfire, you can use IronPython to access a Web Services REST APIs by leveraging existing web libraries. The script example uses the HttpWebRequest library to return JSON from the supplied URL.

     

    from System.Net import HttpWebRequest
    uri = "https://quantprice.herokuapp.com/api/v1.1/scoop/period?tickers=MSFT&begin=2012-02-19""
    webRequest = HttpWebRequest.Create(uri)
    response = webRequest.GetResponse()
     

    The variable response now holds a JSON string.

    In order to parse the JSON string, response has to first be converted into a "stream" using StreamReader()  so it can then be deserialized using the JavaScriptSerializer() and converted into a dictionary.

    from System.IO import StreamReader
    import clr
    clr.AddReference('System.Web.Extensions')
    from System.Web.Script.Serialization import JavaScriptSerializer
    
    streamReader = StreamReader(response.GetResponseStream())
    
    jsonData = streamReader.ReadToEnd()
    
    js = JavaScriptSerializer()
    
    dataDict = js.DeserializeObject(jsonData)
     

    The data can then be looked up using tokens on dataDict:

    myColName = []  # variable used to hold the column names
    for val in dataDict["datatable"]["columns"]:
        myColName.append(val["name"])
    textData =     "t".join(myColName) + "rn"
    
    # build a string representing the data in tab-delimited text format
    for quote in dataDict["datatable"]["data"]:
        #print "t".join(str(val) for val in quote)
        textData += "t".join(str(val) for val in quote) + "rn"
     

    Now that the JSON data has been converted into a string, it now can be converted into a stream format that can then be added into a Spotfire Data Table.

    # make a stream from the string
    stream = MemoryStream()
    writer = StreamWriter(stream)
    writer.Write(textData)
    writer.Flush()
    stream.Seek(0, SeekOrigin.Begin)
     

    Create a Spotfire Data Table column structure with the same column structure as the dataset format using the TextDataReaderSettings():

    # set up the text data reader
    readerSettings = TextDataReaderSettings()
    readerSettings.Separator = "t"
    readerSettings.AddColumnNameRow(0)
    readerSettings.SetDataType(0, DataType.String)
    readerSettings.SetDataType(1, DataType.String)
    readerSettings.SetDataType(2, DataType.String)
    readerSettings.SetDataType(3, DataType.String)
    readerSettings.SetDataType(4, DataType.String)
    readerSettings.SetDataType(5, DataType.String)
    readerSettings.SetDataType(6, DataType.Date)
    readerSettings.SetDataType(7, DataType.Currency)
    readerSettings.SetDataType(8, DataType.Currency)
    readerSettings.SetDataType(9, DataType.Currency)
    readerSettings.SetDataType(10, DataType.Currency)
    readerSettings.SetDataType(11, DataType.Real)

    Now use the stream data and the readerSettingscolumn structure to create the Spotfire Data Table using the TextFileDataSource().
     
     # create a data source to read in the stream
     textDataSource = TextFileDataSource(stream, readerSettings)

    In order for the data table to appear inside the Spotfire Interface, it has to be added to the Document.Data.Tables object.  If the table already exists, it can be replaced.
     
    # add the data into a Data Table in Spotfire
    if Document.Data.Tables.Contains("Stock Data"):
         Document.Data.Tables["Stock Data"].ReplaceData(textDataSource)
    else:
         newTable = Document.Data.Tables.Add("Stock Data", textDataSource)
         tableSettings = DataTableSaveSettings (newTable, False, False)
         Document.Data.SaveSettings.DataTableSettings.Add(tableSettings)
     

    Attached is a visual of an example dxp that uses this code. It also leverages the text box to allow the users inputs to dynamically alter the input parameters to the Web Service API request. 

     

    converted-file.thumb.png.4600a5d6e0a24fee917db943e45befc4.png

     

    License:  TIBCO BSD-Style License

     

     


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