Sinuosity Python Script

Question

To start, I'm very new to scripting. On ArcGIS, there is a python script for a Sinuosity tool http://resources.arcgis.com/en/help/main/10.1/index.html#//001500000022000000

I've tried it and it didn't work and so I did some changes to it and while it runs without error, I get no output in my attribute table. What are my errors? What can I do/add to this script to get an output?

import arcpy
import math
import os

#overwrite existing output
arcpy.env.overwriteOutput = True

class Toolbox(object):
    def __init__(self):
        self.label =  "Sinuosity toolbox"
        self.alias  = "sinuosity"

        # List of tool classes associated with this toolbox
        self.tools = [CalculateSinuosity] 

class CalculateSinuosity(object):
    def __init__(self):
        self.label       = "Calculate Sinuosity"
        self.description = "Sinuosity measures the amount that a river " + \
                       "meanders within its valley, calculated by " + \
                       "dividing total stream length by valley length."

    def getParameterInfo(self):
        #Define parameter definitions

        # Input Features parameter
        in_features = arcpy.Parameter(
            displayName="Input Features",
            name="in_features",
            datatype="GPFeatureLayer",
            parameterType="Required",
            direction="Input")

        in_features.filter.list = ["Polyline"]

        # Sinuosity Field parameter
        sinuosity_field = arcpy.Parameter(
            displayName="Sinuosity Field",
            name="sinuosity_field",
            datatype="Field",
            parameterType="Optional",
            direction="Input")

        sinuosity_field.value = "sinuosity"

        # Derived Output Features parameter
            out_features = arcpy.Parameter(
            displayName="Output Features",
            name="out_features",
            datatype="GPFeatureLayer",
            parameterType="Derived",
            direction="Output")

        out_features.parameterDependencies = [in_features.name]
        out_features.schema.clone = True

        parameters = [in_features, sinuosity_field, out_features]        
        return parameters

    def isLicensed(self): #optional
        return True

    def updateParameters(self, parameters): #optional
        if parameters[0].altered:
            parameters[1].value = arcpy.ValidateFieldName(parameters[1].value,parameters[0].value)
        return

    def updateMessages(self, parameters): #optional
        return

    def execute(self, parameters, messages):
        in_features  = parameters[0].valueAsText
        fieldName   = parameters[1].valueAsText

        if fieldName in ["#", "", None]:
            fieldName = "sinuosity"

        arcpy.AddField_management(inFeatures, fieldName, 'DOUBLE')

        expression =
    def getSinuosity(shape):
        length = shape.length
        d = math.sqrt((shape.firstPoint.X - shape.lastPoint.X) ** 2 +
              (shape.firstPoint.Y - shape.lastPoint.Y) ** 2)
        return d/length

    arcpy.CalculateField_management(in_features,fieldName,'getSinuosity(!shape!)','PYTHON_9.3')

Answer 1

Look at the help page What is a Python toolbox? and then scroll to the bottom of the page and look at the code sample. Note how the the function getSinuosity which is the expression is enclosed in 3 single quotes. Your code is not and you do not include it as a parameter in the CalculateField line.