Yes... some more einsum examples. ... View more

A followup to the recent einsum post, but with a field calculator twist   # ---- a numeric field, python expression which uses the shape field to return the longest edge on the perimeter longest_seg(!Shape!) # ---- the code block ----- import json import numpy as np # def longest_seg(a): """Longest edge""" v = json.loads(a.JSON) r = v['rings'] a = np.array(r).squeeze() a = a[0] if a.ndim > 2 else a diff = a[1:] - a[:-1] ret = np.sqrt(np.einsum('ij,ij->i', diff, diff)) val = np.max(ret) return val   lines 12-13 :  really? having to convert to JSON format just to get at the array values? line 14 :  the json format assumes a multipolygon so a nested, nested set of nests of values... numpy squeeze() gets rid of all the extra nesting line 15 :  a check, but used for dimensions > 2, it will take the first part (the outer ring of the first shape) lines 16-17 :  einsum .... read the previous article line 18:  you will get an array of the segment lengths forming the perimeter... this demo is using the max, so modify the code if you want the minimum or the average or the 3rd from the end, etc etc.  Just dont' over-fluff field calculator code to try and do everything line 19  return the value   There really has to be a better way of converting an arcpy shape into another format which can be used without having to use cursors and deal with the featureclass rather than the feature itself.  like make __geo_interface__ read the shape without having to use that in cursors.   ... View more

A smart person and his notation has many practical applications today ... View more

ArcGIS custom toolbox which uses a python script, for updating a mass amount of field aliases at once, using a list of field names and corresponding aliases input by user. Let’s say you have an ArcGIS feature class or table with a bunch of cryptic, abbreviated field names, and you want to add aliases to make them easier to understand. Let’s say you also have a list of field names and corresponding aliases that you have prepared in Excel or whatever. All you need to do is save that list as a CSV file with the field names in the first column and aliases in the second column. Then run this tool. The only inputs required are the feature class and the CSV file. The script uses the arcpy and csv packages. It first reads the CSV file and parses it into a python list where each item in the list is a list containing a field name and alias value. Then it iterates through that list, running an arcpy command that attempts to update the alias for each field name in the list. As the tool is running, it will display a message for each field that gets an updated alias. If a field name from your list does not exist in the feature class, the tool will display a message telling you that and move on to the next one. It should take just a few seconds per field to run. I ran this tool successfully with ArcGIS Desktop 10.5. I believe it could also be tweaked to work on a shapefile instead of a feature class. It’s really a pretty simple script, and I’m probably not the first person to come up with something like this, but I couldn’t find a solution searching elsewhere. Please let me know or suggest changes if it doesn’t work for you. ... View more

A simpler way to use arcpy.List* functions ... View more