[GIS] How to fix the ArcToolbox error TypeError: cannot concatenate ‘str’ and ‘NoneType’ objects

arcpytypeerror

I am trying to run the ExportHTMLImageMaps tool in ArcGIS 10.3.1 to create HTML image maps to be used as static web geographic navigation maps, but I keep getting the Error TypeError: cannot concatenate 'str' and 'NoneType' objects

I checked each field being used in the tool and each is type String, so I'm not sure where to go from here. Below is a screen cap of my error log. I am a novice at Python and troubleshooting code.

Best Answer

Looking at your screen shot and reading the error message it is saying it cannot join None to a string. This is strongly suggesting that the command

arcpy.env.geographicTransformations

is returning None. So you need to look back at your code to identify where, if at all, you are setting this environment setting?

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[GIS] Multivalue parameter as text in Python toolbox – reading in to imported module function

Try using ' '.join(parameters[2].values). It will give you space delimited string instead. Alternately, map them to raster objects with value_list = [arcpy.Raster(val) for val in parameters[2].values]

[GIS] cannot concatenate str and list objects

I believe you want something like below. rList is a list. It will concatenate with a string, but proabably not as you are expecting.

>>> l1 = ['cat','dog','mouse','monkey','elephant']
>>>'I1986_' + str(l1[0:3])
"I1986_['cat', 'dog', 'mouse']"

Python creates a string representation of the 1st 3 elements in the list. That is why the 1st iteration succeeds, but then the next fails and reports that the object already exists. This would rename all of your objects to the same name.

You're already looping through the list, so use your looping variable to concatenate with the elements of the list.

for raster in rList:
    newName = 'I1986_{}'.format(raster[0:3])
    arcpy.Rename_management(raster, newName)

Best Answer

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[GIS] cannot concatenate str and list objects

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