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Union analysis fails to execute

RichardThurau

Anyone see what's causing this tool to fail?

Gridnums = range(1,18)

for i in Gridnums:
    #vis6class = ws + "/" + "TVvis6class_G" + str(i)
    inList = arcpy.ListFeatureClasses("*ProcGrid_"+str(i), "")
    print "inList: " + str(inList)
    arcpy.Union_analysis(InList, ws + "/" + "TVvis6class_G" + str(i))

Error Code:
inList: [u'Road_ProcGrid_1', u'FPs_S_ProcGrid_1', u'er_di_ProcGrid_1', u'TV_v_ProcGrid_1']

Traceback (most recent call last):
File "E:\Projects\TV\01_Python\LandCover\LC_2_Vector_Tile_6class_091312.py", line 48, in <module>
arcpy.Union_analysis([InList], ws + "/" + "TVvis6class_G" + str(i))
File "C:\Program Files\ArcGIS\Desktop10.0\arcpy\arcpy\analysis.py", line 483, in Union
raise e
RuntimeError: Object: Error in executing tool
>>>

It's making a good list. I've tried messing with the output format.

Any suggestions, much appreciated!!

Rich

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Accepted answers

RichardThurau

Turns out I had an empty geography as one of my union inputs. When I tested the tool, it was within a study site where the geography had data. The first union the code was calling was using a dataset that had no data in the analysis area.

RT

All comments

XanderBakker

One thing that I would advise, in case there is any doubt about how the parameters should be provided, is to execute the tool manually and copy the python code from the Results window. This shows how the parameters should be provided. In case you feel that the help does not reflect clearly how things the tool should be used, you can use the "Feedback on this topic" link in the lower right part of the Help topic. I have used it several times and Esri has responded very fast (mostly the same day).

ChristopherThompson

Reading help on the union command (v10.1 ArcGIS Help 10.1 ) it does say that the input features argument is a list, and shows the proper formatting as a Python list which is enclosed in square brackets - this is also true of v10.0. This is confusing somewhat because the way this is depicted in the help doc is somewhat ambiguous. Help for earlier versions of ArcGIS (v9.3 ArcGIS Desktop Help 9.3 - union (analysis) ) also speak of the input_features argument as being a list but doesn't appear to require this to be formatted as a Python list - makes me think that the tool had a process working in the background to create a Python list from the user supplied input. Ultimately its better that the language in the tools and help are more aligned with the Python terminology so when reference is made to a list it is truly meant to a Python list which has a specific meaning when scripting the command, but it would be nice if this was more clearly stated for those who have worked with legacy products.

JamieKass

Just solved it. I never had this issue before, but perhaps this is a new limitation in 10.1? The input parameter to Union must be a list, at least in my case. I put the single input into a list, i.e.

arcpy.Union_analysis([input], output)

and my tool runs smoothly. If this is a hard rule, it should be emphasized in the tool help.

JamieKass

I am getting the exact same error, but my input is just one feature class (in order to find overlapping regions). It is called within a Python Toolbox workflow, and consistently throws this error. When I run it outside the tool run session, it works fine. Maddening. Any clues as to what might be going on?

ChristopherThompson

Don't you just hate that? Glad you found the error!

RichardThurau

ThomasEmge

Please do print the variable vis6classi and take a look what it currently contains.

My guess would be that it is pointing to a location/workspace that isn't correctly formulated.

If you are able to post your complete script or a more extended section showing where the workspace originates that would be great.

Thanks,
- Thomas

RichardThurau

No Dice. Took a while to get back to this.

Another one of these cases where a lot of people are looking but no one has any suggestions?

Am I doing something so fundamentally wrong that folks think it's hopeless?

Is there a better way to line this up that makes sense?

Is this really something that shouldn't be going wrong, but is?

Do I need to post more info? The error code is exceptionally meaningless in this case.

I really don't want to revert to using ArcToolbox. Please, please!

Current code:

for i in Gridnums:
    vis6classi = "'" + ws + "/" + "TVvis6class_G" + str(i) + "i" + "'"
    inList = arcpy.ListFeatureClasses("*ProcGrid_"+str(i), "")
    print "inList: " + str(inList)
    arcpy.Union_analysis(InList, vis6classi)
    print "Union completed for Grid " + str(i)

same error.

RT

ChristopherThompson

I suspect they way the output is being created is your problem

ws + "/" + "TVvis6class_G" + str(i))

See if you can enclose that entire term inside double quotes and see if that works out.
So something like this might be what it looks like:

"'" + ws + "/" + "TVvis6class_G" + str(i)) + "'"

RichardThurau

True. I am Info (advanced). Manually using the tool works fine, so error must be in the Python.

Thanks.

RT

ChristopherThompson

Out of curiousity what license level are you running? and how many items are in inList? If you are at anything below the ArcInfo (or perhaps advanced i think is the new terminology.. ?) I don't think the union tool accepts more than two inputs.

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