Setting a string Output parameter from the python script tool in ArcGIS

Question

import sys, arcpy  
arcpy.env.workspace = "C:\Scratch"  
Environment_Index = arcpy.GetParameterAsText(0)  
Measure = arcpy.GetParameterAsText(1)  
if Environment_Index == "Percentage of Environmental Hazard":  
    if Measure == "0-25%":   
        Expression = '"per_Envi_H" >0 AND "per_Envi_H" <25'  
    elif Measure == "25-50%":  
        Expression = '"per_Envi_H" >25 AND "per_Envi_H" <50'  
    elif Measure == "50-75%":  
        Expression = '"per_Envi_H" >50 AND "per_Envi_H" <75'  
    elif Measure == "75-100%":  
        Expression = '"per_Envi_H" >75 AND "per_Envi_H" <100'  
    else:  
        Expression = "0"  
    print Expression  
    arcpy.SetParameter(2, Expression)  

elif Environment_Index == "Percentage of Flooded Area":  
    if Measure == "0-25%":  
        Expression = '"Per_Flood" > 0 AND "Per_Flood" <25'  
    elif Measure == "25-50%":   
        Expression = '"Per_Flood" > 25 AND "Per_Flood" <50'  
    elif Measure == "50-75%":  
        Expression = '"Per_Flood" > 50 AND "Per_Flood" <75'  
    elif Measure == "75-100%":   
        Expression = '"Per_Flood" > 75 AND "Per_Flood" <100'  
    else:  
        Expression = "0"  
    print Expression  
    arcpy.SetParameter(2, Expression)  
else:  
    if Measure == "0-50kgs/yr":  
        Expression = '"pest_kg" >0 AND "pest_kg" <50'  
    elif Measure == "50-100kgs/yr":  
        Expression = '"pest_kg" >50 AND "pest_kg" <100'  
    elif Measure == "100-250kgs/yr":  
        Expression = '"pest_kg" >100 AND "pest_kg" <250'  
    elif Measure == "250-500kgs/yr":  
        Expression = '"pest_kg" >250 AND "pest_kg" <500'  
    else:  
        Expression = "0"  
    print Expression  
    arcpy.SetParameter(2, Expression)

I am trying to get a string as an output parameter from the script tool and use the string as the expression for the select by attribute tool.

My user wanted to have a range of values to be selected from a field, I thought it was an easy process by writing a python code.

I tried using the set parameter for the output parameter. I don't understand where the problem is. This is my script tool in the model builder

Answer 1

I guess double-quotes are making trouble. When you use Query Builder, you see that the field names are added without double quotes.

Use your code like that:

import arcpy, sys

arcpy.env.workspace = "C:/Scratch"

environment_index = arcpy.GetParameterAsText(0)
measure= arcpy.GetParameterAsText(1)

if environment_index == "Percentage of Environmental Hazard":
    if measure== "0-25%":   
        expression = 'per_Envi_H > 0 AND per_Envi_H < 25'  
    elif measure== "25-50%":  
        expression = 'per_Envi_H > 25 AND per_Envi_H < 50'  
    elif measure== "50-75%":  
        expression = 'per_Envi_H > 50 AND per_Envi_H < 75'  
    elif measure == "75-100%":  
        expression = 'per_Envi_H > 75 AND per_Envi_H < 100'  
    else:  
        expression = "0"  

elif environment_index == "Percentage of Flooded Area":  
    if measure == "0-25%":  
        expression = 'Per_Flood > 0 AND Per_Flood < 25'  
    elif measure == "25-50%":   
        expression = 'Per_Flood > 25 AND Per_Flood < 50'  
    elif measure == "50-75%":  
        expression = 'Per_Flood > 50 AND Per_Flood < 75'  
    elif measure == "75-100%":   
        expression = 'Per_Flood > 75 AND Per_Flood < 100'  
    else:  
        expression = "0"   

else:  
    if measure == "0-50kgs/yr":  
        expression = 'pest_kg > 0 AND pest_kg < 50'  
    elif measure == "50-100kgs/yr":  
        expression = 'pest_kg > 50 AND pest_kg < 100'  
    elif measure == "100-250kgs/yr":  
        expression = 'pest_kg > 100 AND pest_kg < 250'  
    elif measure == "250-500kgs/yr":  
        expression = 'pest_kg > 250 AND pest_kg < 500'  
    else:  
        expression = "0"  

arcpy.SetParameter(2, expression)

if statement doesn't define a scope in Python. So, you don't have to use arcpy.SetParameter() in every if branch.