# Calculate sequential ID field using ArcGIS Field Calculator? [closed]

In this example, previously posted as Calculating sequential numbers into sorted table using ArcGIS Desktop? :

How do you construct a Python code that would give the Seq field sequencing such as:

1963.......1
1963.......1
1965.......2
1966.......3
1967.......4
1967.......4
1967.......4
1968.......5

Etc.... ???

## closed as off-topic by PolyGeo♦Jun 1 '18 at 12:40

This question appears to be off-topic. The users who voted to close gave this specific reason:

• "When seeking help to debug/write/improve code always provide the desired behavior, a specific problem/error and the shortest code (as formatted text, not pictures) needed to reproduce it in the question body. Providing a clear problem statement and a code attempt helps others to help you." – PolyGeo
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• Welcome to GIS SE. As a new user, please take the Tour. Coding questions here are expected to contain code. You reference "previously posted" without a link. Please Edit the question. – Vince Jun 1 '18 at 11:53
• @Charles, hey do you want the Seq field to be unique or you want it to be based on the Year field (that is all 1963 years will have 1 in the Seq and all 1965 will have 2 in the Seq)? In the question body you duplicate values, but in the screenshot you don't, I am puzzled. – Alex Tereshenkov Jun 1 '18 at 12:06
• I would like it to be based on the year field but same year should have the same seq value. – Charles Jun 1 '18 at 12:08
• This references: gis.stackexchange.com/questions/193681/… – Charles Jun 1 '18 at 12:10
• You could create a csv file with two columns (Years and corresponding Seq codes - a couple of minutes in a spreadsheet). Read the csv file into a python dictionary with Years as keys and Seq code as values. With the update cursor you can write the right Seq value for the corresponding Year into your feature table. – ZrSiO4 Jun 1 '18 at 16:28

You should be able to get the attribute values for a given feature, and then do the following field calculator operation for all features:

Seq = Year - (year zero)

So for your example it would be Seq = Year - 1962

These two pages for ArcGIS for Desktop and ArcGIS Pro have further details on how to do this and other field calculator operations, including some example python scripts.

• Can you give a few more details on where you're getting stuck? This page has a lot more specific syntax details on arcpy.CalculateField_management() desktop.arcgis.com/en/arcmap/10.3/tools/data-management-toolbox/… – ycartwhelen Jun 1 '18 at 13:31
• How do you construct a code to accomplish the pattern above, where for the same year value, Seq value is the same but for the next year it updates bu an increment of 1, etc? – Charles Jun 1 '18 at 13:55
• That's the whole idea behind subtracting the year zero value. In your example: 1963 - 1962 = 1, 1964 - 1962 = 2, 1965-1962 = 3, etc. Although now I take a second look your example doesn't do this exactly (differently in the text and the picture). Are you intentionally skipping 1964=2, or is that a typo? – ycartwhelen Jun 1 '18 at 18:12
• No; and would the sequence be the same for each occurrence of say 1967, etc.? – Charles Jun 1 '18 at 18:30
• The OP is confusing because the two images are inconsistent: in the first example Seq increments by one only when Year changes, but in the second example Seq increments for each record. – Stu Smith Jun 3 '18 at 17:16