topic Re: Calculate value function that reads feature class path in Python Questions

Calculate value function that reads feature class path

2Quiker — Mon, 29 Aug 2022 19:47:00 GMT

I know I can do it with Dissolve, but the issue with Dissolve is that it creates a separate layer and I know I can do this a script but I need to in Model Builder. I need the function to merge feature class based on two attributes. Can this be down with Calculate value in model builder? I have tried the following, but it never seems to finish the process. The model function does seem to work, I check the feature class and the feature class features are merged. I have to manually hit stop.

Expression:

f(fc)

Code block:

import sys, arcpy, os from arcpy import env from arcpy import da from itertools import groupby from operator import itemgetter from functools import reduce fc = r"C:/TEMP/FEMA.gdb/FEMA_TempLyrs" def f(fc): case_fields = ["FLD_ZONE",'ZONE_SUBTY'] # field(s) to group records for merging sort_field, sort_order = "OBJECTID", "ASC" shape_field = "SHAPE@" fields = case_fields + [sort_field, shape_field] sql_orderby = "ORDER BY {}, {} {}".format(", ".join(case_fields), sort_field, sort_order) with da.UpdateCursor(fc, fields, sql_clause=(None, sql_orderby)) as cur: case_func = itemgetter(*range(len(case_fields))) merged_polys = { key:reduce(arcpy.Geometry.union, (row[-1] for row in group)) for key, group in groupby(cur, case_func) } cur.reset() for key, group in groupby(cur, case_func): row = next(group) cur.updateRow(row[:-1] + [merged_polys[key]]) for row in group: cur.deleteRow() del cur return fc

Re: Calculate value function that reads feature class path

Anonymous User — Tue, 30 Aug 2022 18:08:50 GMT

I would look at separating your operations. If you are building a dictionary in the first part, do that in a SearchCursor. Drop the cur.reset(). Then with an UpdateCursor, iterate over the key, group dictionary and do your update.

Re: Calculate value function that reads feature class path

2Quiker — Wed, 31 Aug 2022 15:46:50 GMT

Thanks for the reply, I guess I am not understand how to put the code/model together to work.

Is there another way that this can be accomplished?

Re: Calculate value function that reads feature class path

Anonymous User — Wed, 31 Aug 2022 17:50:49 GMT

This is untested and to just show you the splitting of two operations that you are doing that I think would replace the reset(). Probably need an iterator in the each cursor somewhere? That's something you'll have to test and see.

merged_polys = None with da.SearchCursor(fc, fields, sql_clause=(None, sql_orderby)) as cur: case_func = itemgetter(*range(len(case_fields))) merged_polys = { key:reduce(arcpy.Geometry.union, (r[-1] for r in group)) for key, group in groupby(row, case_func) } with da.UpdateCursor(fc, fields, sql_clause=(None, sql_orderby)) as uCur: for key, group in groupby(uCur, case_func): row = next(group) uCur.updateRow(row[:-1] + [merged_polys[key]]) for row in group: uCur.deleteRow()

Alternative is add print statements to see where it is getting stuck in the loop and go from there.

Re: Calculate value function that reads feature class path

2Quiker — Fri, 02 Sep 2022 22:26:56 GMT

Sorry for the late response. I wasn't sure if you meat separate the two into two separate calculate values, how I was suppose to call the first calculate value to the second calculate value. So I figured why the model didn't stop, FLD_ZONE had some empty attributes.

I tried the following it runs but nothing is merged, no errors.

fc = r"C:\Temp\FEMA.gdb\FEMA_TempLyrs def f(fc): case_fields = ["FLD_ZONE",'ZONE_SUBTY'] # field(s) to group records for merging sort_field, sort_order = "OBJECTID", "ASC" shape_field = "SHAPE@" fields = case_fields + [sort_field, shape_field] sql_orderby = "ORDER BY {}, {} {}".format(", ".join(case_fields), sort_field, sort_order) with da.UpdateCursor(fc, fields, sql_clause=(None, sql_orderby)) as cur: for row in cur: print (row) if row[0] == None: case_func = itemgetter(*range(len(case_fields))) merged_polys = { key:reduce(arcpy.Geometry.union, (row[-1] for row in group)) for key, group in groupby(cur, case_func) } cur.reset() for key, group in groupby(cur, case_func): row = next(group) cur.updateRow(row[:-1] + [merged_polys[key]]) for row in group: cur.deleteRow() del cur return fc

I also tried separating the operations like you stated but nothing gets merged, with error.

Error:

ERROR 000539: Traceback (most recent call last):
File "<expression>", line 1, in <module>
File "<string>", line 38, in fc1
TypeError: 'NoneType' object is not subscriptable

import sys, arcpy, os from arcpy import env from arcpy import da from itertools import groupby from operator import itemgetter from functools import reduce fc = r"C:\Temp\FEMA.gdb\FEMA_TempLyrs" def f(fc): case_fields = ["FLD_ZONE",'ZONE_SUBTY'] # field(s) to group records for merging sort_field, sort_order = "OBJECTID", "ASC" shape_field = "SHAPE@" fields = case_fields + [sort_field, shape_field] sql_orderby = "ORDER BY {}, {} {}".format(", ".join(case_fields), sort_field, sort_order) merged_polys = None with da.SearchCursor(fc, fields, sql_clause=(None, sql_orderby)) as cur: case_func = itemgetter(*range(len(case_fields))) for row in cur: print (row) if row[0] == None: merged_polys = { key:reduce(arcpy.Geometry.union, (row[-1] for row in group)) for key, group in groupby(cur, case_func) } else: pass del cur with da.UpdateCursor(fc, fields, sql_clause=(None, sql_orderby)) as uCur: for key, group in groupby(uCur, case_func): row = next(group) uCur.updateRow(row[:-1] + [merged_polys[key]]) for row in group: uCur.deleteRow() return fc