[GIS] Looping through multiple feature datasets and Intersect Files

arcpy

I am getting an error with a python script I have created. I have 1 geodatabase with 3 feature datasets. What I would like to do, is loop through 1 feature dataset (NB) to get a list of feature classes. One by one, I would like to get the name of the feature class (ID_NB) and search for its corresponding feature class in another dataset (called CCH) so that I can perform the Intersect function on the two files and save the output in the 3rd feature dataset and call it ID_Ints. **There may not always be a matching feature dataset between the two either.

The script works fine the first time through, but when it comes to the second feature class, it gives me an error saying "Dataset does not exist or is not supported". I have a feeling it is because I have switched workspaces in a for loop, but I can't think of another way around this.

Anyone have any ideas?

#Define Environments
CCHws = "C://TEST.gdb//CCH"
PerMap = "C://TEST.gdb//NB"
opws = "C://TEST.gdb//opws"

#Set workspace
arcpy.env.workspace = PerMap
arcpy.env.overwriteOutput = True
NBList = arcpy.ListFeatureClasses()

#Start forloop, find first NB Feature Class and extract the ID (the first 5 characters)
for NB in NBList:
    NBname = NB[:5]
    NBname2 = NBname + "*"
    NBnameEx2 = "\"" + NBname2 + "\""

#Calculate Original Area of NB feature Class
    arcpy.AddField_management(NB, "NB_Area", "DOUBLE")
    arcpy.CalculateField_management(NB,"NB_Area","!shape.area@meters!","PYTHON")

#Set variables to use in Intersect
    CCH = str(CCHws) + "//" + str(NBname) + "_CCH" 
    opresult = opws + "//" + str(NBname) + "_Ints"
    NBfile = str(PerMap) + "//" + str(NBname) + "_NB"

#Re-set workspace to look for matching ID with an '_CCH' in the CCH dataset
    arcpy.env.workspace = CCHws
    arcpy.env.overwriteOutput = True
    cchList = arcpy.ListFeatureClasses(NBname2)
    for cch in cchList:
        if len(cchList) > 0:
            arcpy.Intersect_analysis([NBfile,CCH],opresult)  
        else:
            print NBname + " Does not have a matching CCH"

Best Answer

You are correct. You need to reset your workspace again at the end of your nested for loop (CCH in cchList). Try this:

#Re-set workspace to look for matching ID with an '_CCH' in the CCH dataset
    arcpy.env.workspace = CCHws
    cchList = arcpy.ListFeatureClasses(NBname2)
    for cch in cchList:
        if len(cchList) > 0:
           arcpy.Intersect_analysis([NBfile,CCH],opresult)  
        else:
            print NBname + " Does not have a matching CCH"
    arcpy.env.workspace = PerMap

You also only need to specify the arcpy.env.overwriteOutput = True once at the top of the script like you have so I removed the second reference to it in your nested for loop. Hope this helps.

Related Solutions

[GIS] Batch renaming of feature datasets, and feature classes based on new dataset name

A good solution is a combination of ListDatasets() and Rename().

The basic solution is:

Set your workspace
Use arcpy.ListDatasets() to get a list of all datasets.
Loop through the datasets list
For each dataset in the list, call arcpy.Rename_management(oldName, newName)
If the names are as you stated in your post, then the newName is 'gen26_' + oldName.split(':')[1]

To do the same now for each feature class within the datasets.

Set your workspace
Use arcpy.ListDatasets() to get a list of all the datasets (since you just renamed them)
For each dataset in the list, change the workspace to be that dataset
Now call arcpy.ListFeatureClasses() to get a list of the feature classes
Use arcpy.Rename_management() like above with the new name

Note you can easily combine the above steps if you list datasets, list the feature classes in the workspace, rename all the feature classes, and now you can rename the dataset as well. For more on string manipulation, read here

[GIS] Loop with arcpy.ListFiles

The ModelBuilder functions (like arcpy.IterateFiles_mb) only work within ModelBuilder, and don't do as desired within a Python script. But, for loops do just as well (if not better).

In this case, you want to loop through all the .asc files in a workspace.

Define the workspace (you got that far):

import arcpy
from arcpy import env

env.workspace = r"D:\Julia_T\projekt\MODIS\karadarya\2000_neu\testdatenB"

Use the List Files function to create a list of all the .asc files in the workspace

ascFileList = arcpy.ListFiles("*.asc")
for ascFile in ascFileList:
    # geoprocessing steps

Or, a simpler version that does the same thing:

for ascFile in arcpy.ListFiles("*.asc"):
    # geoprocessing steps

Run arcpy tools on each file by putting them under the for loop. (Note: pay attention to indentation. It is one of the few things Python is picky about.)

for ascFile in arcpy.ListFiles("*.asc"):
    # get the file name without extension (replaces the %Name% variable from ModelBuidler)
    ascFileName = os.path.splitext(ascFile)[0]
    # define the output file
    rastFile = ascFileName + "_output.img"
    # run the tool
    arcpy.ASCIIToRaster_conversion(ascFile, rastFile, "INTEGER")

A couple of notes about exported python scripts -- not only do iterators not work, but the tool syntax is old (for example, arcpy.gp.ASCIIToRaster should now be arcpy.ASCIIToRaster_conversion. I always recommend quickly looking up the ArcGIS Help pages for any given geoprocessing function to see what the current syntax and input variables should be. It is often faster to make the script from scratch instead of exporting a ModelBuilder tool and cleaning up the code.

Best Answer

Related Solutions

[GIS] Batch renaming of feature datasets, and feature classes based on new dataset name

[GIS] Loop with arcpy.ListFiles

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