TypeError: cannot concatenate 'str' and 'NoneType' objects
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() -- http://mail.python.org/mailman/listinfo/python-list
Re: TypeError: cannot concatenate 'str' and 'NoneType' objects
[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-program-what-should-i-do for details. /F -- http://mail.python.org/mailman/listinfo/python-list
Re: TypeError: cannot concatenate 'str' and 'NoneType' objects
# 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() Warning: I know nothing about the Python ArcGIS stuff. The first thing that jumps out at me is your while condition. You are testing Townshps when it seems from the code that you should be testing Townshp. However, the typical Python way to iterate through a list for be to use a for loop. Perhaps replace the while statement with: for Townshp in Townshps: and remove the Townshp = Townshps.next() lines If that doesn't do it, please post the entire traceback message that you are seeing (copy and paste it) and it should tell us a lot more about your error. -- http://mail.python.org/mailman/listinfo/python-list
Re: TypeError: cannot concatenate 'str' and 'NoneType' objects
On Wed, 2006-12-20 at 20:22 +0100, Fredrik Lundh 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. Actually those will both lead to an infinite loop, since you're comparing the entire list, which is unlikely to ever become or None. You should compare Townshp, not Townshps, to or None, whichever the .next() method actually returns to signal the end of the list. Then again, I have the sneaking suspicion that you didn't post the actual code that you're running. The code you posted looks like it should raise a NameError in the line that says Townshp = Townshps.next(). -Carsten -- http://mail.python.org/mailman/listinfo/python-list
Re: TypeError: cannot concatenate 'str' and 'NoneType' objects
Fredrik Lundh wrote: while Townshps is not None: or rather, while Townshp is not None: since that's the variable you're using later on. /F -- http://mail.python.org/mailman/listinfo/python-list
Re: TypeError: cannot concatenate 'str' and 'NoneType' objects
Mark Peters wrote: However, the typical Python way to iterate through a list for be to use a for loop. Perhaps replace the while statement with: for Townshp in Townshps: and remove the Townshp = Townshps.next() lines that assumes that the feature class list is actually a Python iterable, of course, and not just something that happens to have a next method. ::: ... and judging from the documentation http://webhelp.esri.com/arcgisdesktop/9.1/index.cfm?TopicName=ListFeatureClasses%20method it's not an iterable. ::: you could of course replace the fcs = gp.ListFeatureClasses() fc = fcs.next() while fc: ... fc = fcs.next() pattern with for fc in iter(gp.ListFeatureClasses().next, None): ... but maybe that's a bit too clever for an absolute novice ;-) /F -- http://mail.python.org/mailman/listinfo/python-list
Re: TypeError: cannot concatenate 'str' and 'NoneType' objects
[EMAIL PROTECTED] a écrit : 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. Please post the full traceback. It's meant to help finding out what went wrong, you know... 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's certainly not the solution... Please when someone responds, please treat me as an absolute novice. Thank you, Marisa Here is my code: (snip) #Get list of Town Shapefiles Townshp = gp.ListFeatureClasses (*) (snip) Townshp = Townshps.next() while Townshps !=: 1/ where does this Townshps comes from ? 2/ naming conventions are to use either all_lower (preferred) or at least mixedCase names for variables. And by all mean be consistent. 3/ if Townshp is a shortcut for Township, then it would be better to keep the full word 4/ the Python 'for' loop is meant to iterate over an iterable and taking care of boundaries, so you'd be better using it: townships = gp.ListFeatureClasses (*) for township in townships: doSomethingWith(township) -- http://mail.python.org/mailman/listinfo/python-list
Re: TypeError: cannot concatenate 'str' and 'NoneType' objects
Bruno Desthuilliers a écrit : [EMAIL PROTECTED] a écrit : 4/ the Python 'for' loop is meant to iterate over an iterable and taking care of boundaries, so you'd be better using it: townships = gp.ListFeatureClasses (*) for township in townships: doSomethingWith(township) Actually, forget the for loop (cf Fredrik's post - looks like gp.ListFeatureClasses() doesn't return an iterable...) -- http://mail.python.org/mailman/listinfo/python-list
Re: TypeError: cannot concatenate 'str' and 'NoneType' objects
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 -- http://mail.python.org/mailman/listinfo/python-list
Re: TypeError: cannot concatenate 'str' and 'NoneType' objects
On Wed, 2006-12-20 at 11:33 -0800, Mark Peters wrote: Warning: I know nothing about the Python ArcGIS stuff. The first thing that jumps out at me is your while condition. You are testing Townshps when it seems from the code that you should be testing Townshp. However, the typical Python way to iterate through a list for be to use a for loop. Perhaps replace the while statement with: for Townshp in Townshps: I was considering suggesting this, but I'm not sure there is much hope that this would work. The posted code suggests that Townshps.next() returns or None when the end of the list is reached. In order for the for loop to work, it would have to raise StopIteration instead. (I suppose it is conceivable that iter(Townshps) would return an object that does behave in the required manner, but I wouldn't bet a lot of money on that.) Of the course if Townshps does not support the iteration protocol, the for loop could still be written using the iter(callable,sentinel) pattern, but let's not confuse this poor newbie more than necessary ;) -Carsten -- http://mail.python.org/mailman/listinfo/python-list
