topic Re: Populate rows using Update Cursor based on a list of repeating values in Python Questions

Populate rows using Update Cursor based on a list of repeating values

ZacharyHart — Fri, 09 Sep 2016 15:47:28 GMT

I've been searching high and low for this (Stackoverflow/exchange, etc, Geonet...). Here it goes. I have a table with a number of records. I have a field called 'Rotation' I would like to populate with a repeating set of values [0,90,180,270]. So imagine the following:

PT_ID	ROTATION
1	0
2	90
3	180
4	270
5	0
6	90
7	180
8	270
9	0

I've tried to simplify my question as much as possible, but its literally as simple as that. Most of the searches return information related to deleting duplicate/repeated records & values.

Re: Populate rows using Update Cursor based on a list of repeating values

JoshuaBixby — Sun, 12 Dec 2021 01:52:59 GMT

itertools.cycle()

Haven't tested but something like:

>>> from itertools import cycle
>>> rot = cycle((0,90,180,270))
>>> with arcpy.da.UpdateCursor(in_table,["PT_ID","ROTATION"]) as cur:
...     for row in cur:
...         row[1] = next(rot)
...         cur.updateRow(row)‍‍‍‍‍‍

Re: Populate rows using Update Cursor based on a list of repeating values

ZacharyHart — Fri, 09 Sep 2016 18:42:58 GMT

Joshua, this is exactly what I needed, thanks!!!

Re: Populate rows using Update Cursor based on a list of repeating values

DarrenWiens2 — Fri, 09 Sep 2016 18:59:54 GMT

Go with Joshua's answer, I was just curious to see how hard this would be in Field Calculator (as long as your IDs are reliable):

VB Script (but could do the same in Python): (([PT_ID]-1)*90)-( Int(([PT_ID]/4)-0.25) *360)