geoprocessing describe geometry object object

ZacharyUhlmann1

Hi,

I am developing (slowly) workflows to script geoprocessing tasks using Python and Arcpy (along with the other common suspects - pandas, numpy, etc.).  I want to operate using the 'in_memory' workspace OR (situation-dependent) use `arcpy.da.SearchCursor...` to access rows and return objects, perform geoprocessing tasks like merge, union, append, etc. to avoid creating intermediate data. 

ArcMap 10.6.1

Yesterday I created a function that basically does this:

 

 

 

 

def extract_cursor(fcs_list, target_field_list, target_val_list, fname):
    for i in range(len(fcs_list)):
        fcs = fcs_list[i]
        target_field = target_field_list[i]
        target_val = target_val_list[i]
        with arcpy.da.SearchCursor(fcs, [target_field, 'SHAPE@']) as cursor:
                for row in cursor:
                    # select rows with matching vals
                    if target_val in row:
                        # initiate new feature
                        if 'shapes_union' not in locals():
                            # get geometry object - Polyline in my case
                            shapes_union = row[1]
                        else:
                            # merge new geometry objects to build one containing 
                            # all features/rows matching selection criteria
                            shapes_union = shapes_union.union(row[1])
    arcpy.CopyFeatures_management(shapes_union, fname)

 

 

 

 

 

Then I run the function as such (pretend it's housed here: 'path/to/zachs_arc_scripts/zachs_geo_script.py')

 

 

 

 

import sys
sys.path.append('path/to/zachs_arc_scripts')
from zachs_geo_script import extract_cursor

fcs_in ['kentucky','missouri','kansas']
target_field = ['rivers','streams','rivers']
target_val = ['rural','rural','seasonal']
fname = 'merged_rivers_ky_mo_ks'
extract_cursor(fcs_in, target_field, target_val, fname)

 

 

 

 

 

To be honest I originally had this functioning the exact same nested in a class, and instead of a list I saved variables in a csv.  Then passed the csv and extracted the list of variables via a pandas dataframe.  But I figured this was easier to see for feedback purposes.

PROBLEM!  the feature class merged_rivers_ky_mo_ks will be created, but it contains just one val or is empty.  So to troubleshoot I decomposed the function and ran it directly in the Python Window and it works!  The problem is that when run in the Python Window the geometry object is this:

row[1]

<Polyline object at xyz>

but within the function run through the Window (as described above) - I get this:

row[1]

>>>geoprocessing describe geometry object object at xyz>

Furthermore, if I 

return(row[1])

within the function I return the proper Polyline object not the geoprocessing describe geometry...

So the problem is arising from this object type which I can only find sparse info on.

Please help with knowledge on this specific object and issue or offer suggestions for alternate workflows.  I really want to get some decent geoprocessing scripts going, but I keep running into inexplicable issues like this.  Thanks!  Zach

JohannesLindner

I could reproduce the different object types when manually running the commands in the python window (<Polygon object at ...>) vs running the function (<geoprocessing describe geometry object at ...>).

I could not reproduce your problem (empty output).

You also said one value in the output was an error, but that should be the expected outcome when merging all found features, right?

I edited your code, as I couldn't use yours with my data structure and multiple features. Maybe it works better for you.

# fcs_list: list of paths to the feature classes
# where_clauses: list of where clauses used to select only certain entries from a feature class ("SELECT * FROM feature_class WHERE ...")
# fname: path to the output feature class


def extract_cursor(fcs_list, where_clauses, fname):
    # ensure correct input
##    if len(fcs_list) != len(where_clauses):
##        raise ValueError("fcs_list and where_clauses have to be the same length!")
##    desc_list = [arcpy.da.Describe(fc) for fc in fcs_list]
##    if not all([desc["dataType"] == "FeatureClass" for desc in desc_list]):
##        raise ValueError("All elements of fcs_list have to be feature classes!")
##    if len(set([desc["shapeType"] for desc in desc_list])) > 1:
##        raise ValueError("All elements of fcs_list have to be of the same geometry type!")

    # extract all applicable shapes from all feature classes
    shapes = []
    for fc, where in zip(fcs_list, where_clauses):
        shapes += [row[0] for row in arcpy.da.SearchCursor(fc, ["SHAPE@"], where)]

    # merge the shapes
    merged_shape = shapes[0]
    for s in shapes:
##        print(s)  # <-- this prints <geoprocessing describe geometry object at ...>
        merged_shape = merged_shape.union(s)

    # save the merged shape
    arcpy.management.CopyFeatures(merged_shape, fname)

 

You can call it like this:

import sys
sys.path.append('path/to/zachs_arc_scripts')
from zachs_geo_script import extract_cursor

fcs_in ['kentucky','missouri','kansas']
where_clauses = ["rivers = 'rural'", "streams = 'rural'", "rivers = 'seasonal'"]
# you can also write more complex queries:
# "rivers IN ('rural', 'seasonal')"
# "TextField = 'text' OR IntField = 5"
# "rivers = 'rural' AND river_length > 9000"
fname = 'merged_rivers_ky_mo_ks'
extract_cursor(fcs_in, where_clauses, fname)