[GIS] How to append Extent object to existing dictionary key values

arcpycursorextents

I have a dictionary whose keys are map segment names, and whose value is a list of three field values.

Using an arcpy.da.SearchCursor on the map segments FeatureLayer, I have extracted the extent object and the names for the segments.

Using the similar map segment names, I want to append the extent values to the dictionary keys (so that I can reference them later). How would I do this, you can't index an Extent object.

for instance:

{'m32': [7, 10, 13], 'm33': [7, 10, 13]}...

turns into something like:

{'m32': [7, 10, 13,XMin,Ymin,XMax,YMax], 'm33': [7, 10, 13,XMin,Ymin,XMax,YMax]}...

so that when I index it, I can index the key, the original values, and index the extent values.

Best Answer

For adding a new items to a python list object use append. The basic syntax is list.append(addedItem). With a dictionary containing a list it is dictionary(key).append(addedItem).

Here is a script skeleton that creates a dictionary which has a list of lists as its value:

 # Set feature class variable
 relateFC = r"C:\Users\OWNER\Documents\ArcGIS\Centerline_Edit.gdb\CL_INTERSECTIONS_PAIRS"  
    # create a field list with the relate field first (ROUTE_NAME),   
    # followed by sort field(s) (MEASURE), then label field(s) (CROSS_STREET)  
    relateFieldsList = ["ROUTE_NAME", "MEASURE", "CROSS_STREET"]  
    # process a da search cursor to transfer the data to the dictionary  
    with arcpy.da.SearchCursor(relateFC, relateFieldsList) as relateRows:  
      for relateRow in relateRows:  
        # store the key value in a variable so the relate value   
        # is only read from the row once, improving speed  
        relateKey = relateRow[0]  
        # if the relate key of the current row isn't found   
        # create the key and make it's value a list of a list of field values  
        if not relateKey in relateDict:  
          # [searchRow[1:]] is a list containing  
          # a list of the field values after the key.  
          relateDict[relateKey] = [relateRow[1:]]  
        else:  
          # if the relate key is already in the dictionary   
          # append the next list of field values to the   
          # existing list associated with the key  
          relateDict[relateKey].append(relateRow[1:])
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