Calculate field of increasing number for each unique value in another field using ArcGIS Pro

Question

I am using ArcGIS Pro 2.3. I have a point layer, for which I need to calculate a unique increasing number. I am trying to calculate a field "BlockUnique" with a sequential number sequence (1, 2, 3, and so on). I have another field "BlockID". I need the BlockUnique field to calculate the increasing number sequence and restart for every unique BlockID. An example below.

Is this able to be done without Python?

If python is required, how would I script this?

I am not even sure where to begin!

Example: BlockID on left, BlockUnique on right.

A 1
A 2
A 3
B 1
B 2
C 1
D 1
D 2

Does this answer your question? Numbering like values in new attribute table field using field calculator of ArcMap — mikewatt, Apr 06 '22 at 21:59
Unfortunately not, i need the numbers to continue for the same letter. — Jessica, Apr 07 '22 at 18:19
Ahh, right. I feel like that question has also come up but I can't seem to find it. — mikewatt, Apr 07 '22 at 19:10
https://gis.stackexchange.com/questions/200150/auto-incrementing-field-based-on-groups-within-feature-class — FelixIP, Apr 07 '22 at 19:18
On a side not, ArcGIS Pro 2.3 was retired by Esri on Jan. 01, 2022; so I suggest upgrading to a supported version if not the latest version. — bixb0012, Apr 17 '22 at 19:58

mikewatt · Answer 1 · 2022-04-16T23:42:20.970

1

If we frame it another way, you basically want BlockUnique to be the number of occurrences of BlockID seen up to the current row.

Code block:

from collections import defaultdict
lookup = defaultdict(int)
def get_id(value):
    lookup[value] += 1
    return lookup[value]

Expression:

get_id(!BlockID!)

edited Apr 16 '22 at 23:42

answered Apr 07 '22 at 19:10

mikewatt

5,083
9
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I love defaultdict but I really dislike global. Fortunately in this case global isn't needed because Python dictionaries are mutable so they are passed by reference, which makes the global/local namespace issue moot when updating contents of the variable. – bixb0012 Apr 16 '22 at 16:04
Good call, edited. – mikewatt Apr 16 '22 at 23:42

fatih_dur · Answer 2 · 2022-04-11T05:08:08.057

0

This is a variation to mikewatt's answer and uses the same logic suggested by FelixIP's link.

Code block

lookup = {}
def get_id(value):
   lookup[value] = lookup.get(value, 0) + 1
   return lookup[value]

Expression

get_id(!BlockID!)

edited Apr 11 '22 at 05:08

answered Apr 11 '22 at 01:28

fatih_dur

4,983
2
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Calculate field of increasing number for each unique value in another field using ArcGIS Pro

2 Answers2