Creating the ArcGIS Desktop Python Toolbox

Almost all tools have parameters. The parameter values will be set by the end user with the Tool dialog box, or they will be hardcoded within the script. When the tool is executed, the parameter values are sent to your tool's source code. Your tool reads these values and proceeds with its work. You use the getParameterInfo() method to define the parameters for your tool. Individual parameter objects are created as part of this process. If necessary, open InsertWildfires.pyt in your code editor and find the getParameterInfo() function in the USGSDownload class. Add the following parameters, and then we'll discuss what the code is doing:

def getParameterInfo(self):

        """Define parameter definitions"""
        # First parameter
        param0 = arcpy.Parameter(displayName="ArcGIS Server Wildfire URL",
                        name="url",
                        datatype="GPString",
                        parameterType="Required",
                        direction="Input")
        param0.value = "http://wildfire.cr.usgs.gov/arcgis/rest/services/geomac_dyn/MapServer/0/query"

        # Second parameter
        param1 = arcpy.Parameter(displayName="Output Feature Class",
                        name="out_fc",
                        datatype="DEFeatureClass",
                        parameterType="Required",
                        direction="Input")

Each parameter is created using arcpy.Parameter and is passed a number of arguments that define the object. For the first Parameter object (param0), we are going to capture a URL to an ArcGIS Server map service containing real-time wildfire data. We give it a display name ArcGIS Server Wildfire URL, which will be displayed on the dialog box for the tool. A name for the parameter, a datatype, a parameter type, and a direction. In the case of the first parameter (param0), we also assign an initial value, which is the URL to an existing map service containing the wildfire data. For the second parameter, we're going to define an output feature class where the wildfire data that is read from the map service will be written. An empty feature class to store the data has already been created for you.

Next we'll add both the parameters to a Python list called params and return, to the list to the calling function. Add the following code:

def getParameterInfo(self):

        """Define parameter definitions"""
        # First parameter
        param0 = arcpy.Parameter(displayName="ArcGIS Server Wildfire URL",
                        name="url",
                        datatype="GPString",
                        parameterType="Required",
                        direction="Input")
        param0.value = "http://wildfire.cr.usgs.gov/arcgis/rest/services/geomac_dyn/MapServer/0/query"

        # Second parameter
        param1 = arcpy.Parameter(displayName="Output Feature Class",
                        name="out_fc",
                        datatype="DEFeatureClass",
                        parameterType="Required",
                        direction="Input")

        params = [param0, param1]
        return params

The main work of a tool is done inside the execute() method. This is where the geoprocessing of your tool takes place. The execute() method, as shown in the following code snippet, can accept a number of arguments, including the tools self, parameters, and messages:

def execute(self, parameters, messages):
        """The source code of the tool."""
        return

To access the parameter values that are passed into the tool, you can use the valueAsText() method. The following steps will guide you through how to add and execute the execute() method:

We'll complete the actual geoprocessing of this tool in the next section.