TypeError: cannot concatenate 'str' and 'NoneType' objects

[thompson . marisa]

Hi.

I'm extremely new to Python and programming as a whole.  I have written
a python script with the assistance of ESRI ArcGIS 9.2, which uses
Python 2.4.1, however, it gives me this error when I try to run it.
I've already posted at ESRI support, and I was hoping that Python
people could help me more.

I hope there is something simple I could do to be able to define the
object that it thinks is NoneType.  Please when someone responds,
please treat me as an absolute novice.

Thank you,
Marisa

Here is my code:

#
---
# towntab92.py
# Created on: Wed Dec 20 2006 11:09:59 AM
#   (generated by ArcGIS/ModelBuilder)
# Created by Marisa Thompson
#
---

# Import system modules
import sys, string, os, arcgisscripting

# Create the Geoprocessor object
gp = arcgisscripting.create()

# Check out any necessary licenses
gp.CheckOutExtension(spatial)

# Load required toolboxes...
gp.AddToolbox(C:/Program Files/ArcGIS/ArcToolbox/Toolboxes/Spatial
Analyst Tools.tbx)

# Define workspace
gp.workspace = F:/Marisa/inputfolder

# Define Variables
raster = F:/Marisa/outputfolder_72/mss-72-spf.img

#Get list of Town Shapefiles
Townshp = gp.ListFeatureClasses (*)

#Store path to output folder
outputPath = F:/Marisa/outputfolder_72

# Begin going through the loop
Townshp = Townshps.next()
while Townshps !=:
#Set the output name to be the same as input
outName = outputPath + / + Townshp + land + .img
Output_table = outputPath + / + Townshp + table + .dbf
#For each extract by Mask
gp.ExtractbyMask_sa (raster, Townshp, outName)
#For each tabluate area
gp.TabulateArea_sa (Townshp, RITOWN5K_, outName, VALUE,
Output_table, 98.425)
Townshp = Townshps.next()

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Re: TypeError: cannot concatenate 'str' and 'NoneType' objects

[thompson . marisa]

I've had a lot of replies suggesting different things.  These are the
results:

When I change

while Townshps !=: to
while Townshp is not None:

and when I change

while Townshps !=: to
for Townshp in iter(gp.ListFeatureClasses().next, None):

They both work perfectly, and it solved my problem.

Thank you all so much.
Marisa


On Dec 20, 2:22 pm, Fredrik Lundh [EMAIL PROTECTED] wrote:
 [EMAIL PROTECTED] wrote:
  I'm extremely new to Python and programming as a whole.  I have written
  a python script with the assistance of ESRI ArcGIS 9.2, which uses
  Python 2.4.1, however, it gives me this error when I try to run it.
  I've already posted at ESRI support, and I was hoping that Python
  people could help me more.

  I hope there is something simple I could do to be able to define the
  object that it thinks is NoneType.that would be the None object.

http://effbot.org/pyref/None

 which is often used as a placeholder in Python.

 my guess is that it's the next() call that returns None when you've
 reached the end of the shapefile list; try changing

  while Townshps !=:

 to

  while Townshps is not None:

 and see if the problem goes away.

 if you still get an exception, please post the full traceback; see

 http://effbot.org/pyfaq/tutor-i-need-help-im-getting-an-error-in-my-p...
 
 for details.
 
 /F

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