Hello,I'm using ArcGIS 10.1 and having trouble trying to set and get an output parameter in the execute() method of a Python toolbox. To illustrate, I've created a simple Python Toolbox which takes two input parameters (a and b) and adds them together to get a single output parameter (total). The code is below. Using arcpy.SetParameterAsText(2, total) to set the output parameter works fine. Logically, after setting the value, I should be able to fetch it using arcpy.GetParameterAsText(2). However, this call always returns None. I instead have to use parameters[2].valueAsText to return the value. There is an inconsistency in the usage of SetParameterAsText and GetParameterAsText. What is the "proper" way to set and get an output parameter in a Python toolbox? The link below explains to use valueAsText to get the values but says nothing about setting parameters.http://resources.arcgis.com/en/help/main/10.1/index.html#//001500000037000000Thanks,Wayne
import arcpy
class Toolbox(object):
def __init__(self):
"""Define the toolbox (the name of the toolbox is the name of the
.pyt file)."""
self.label = "Toolbox"
self.alias = ""
# List of tool classes associated with this toolbox
self.tools = [Tool]
class Tool(object):
def __init__(self):
"""Define the tool (tool name is the name of the class)."""
self.label = "Tool"
self.description = ""
self.canRunInBackground = False
def getParameterInfo(self):
"""Define parameter definitions"""
a = arcpy.Parameter(
displayName = 'a',
name = 'a',
datatype = 'GPLong',
parameterType = 'Required',
direction = 'Input'
)
b = arcpy.Parameter(
displayName = 'b',
name = 'b',
datatype = 'GPLong',
parameterType = 'Required',
direction = 'Input'
)
total = arcpy.Parameter(
displayName = 'Total',
name = 'total',
datatype = 'GPLong',
parameterType = 'Derived',
direction = 'Output'
)
# Set defaults
a.value = 100
b.value = 200
params = [a, b, total]
return params
def isLicensed(self):
"""Set whether tool is licensed to execute."""
return True
def updateParameters(self, parameters):
"""Modify the values and properties of parameters before internal
validation is performed. This method is called whenever a parameter
has been changed."""
return
def updateMessages(self, parameters):
"""Modify the messages created by internal validation for each tool
parameter. This method is called after internal validation."""
return
def execute(self, parameters, messages):
"""The source code of the tool."""
# Print all parameters before any changes are made
ndx = 0
for p in parameters:
arcpy.AddMessage('parameters[%d].valueAsText: %s'% (ndx, p.valueAsText))
arcpy.AddMessage('arcpy.GetParameterAsText(%d): %s' % (ndx, arcpy.GetParameterAsText(ndx)))
ndx += 1
arcpy.AddMessage('=' * 50)
# Set the output parameter
total = int(parameters[0].valueAsText) + int(parameters[1].valueAsText)
arcpy.SetParameterAsText(2, total)
# Print all parameters again
ndx = 0
for p in parameters:
arcpy.AddMessage('parameters[%d].valueAsText: %s'% (ndx, p.valueAsText))
arcpy.AddMessage('arcpy.GetParameterAsText(%d): %s' % (ndx, arcpy.GetParameterAsText(ndx)))
ndx += 1
return
