# \[SOLVED\] How to get a unique list from a bigger list of lists based on 1 criteria **URL:** \ **Category:** General Discussion\ **Created:** [August 22, 2020, 12:25am UTC](https://forum.inductiveautomation.com/t/solved-how-to-get-a-unique-list-from-a-bigger-list-of-lists-based-on-1-criteria/37987 "2020-08-22T00:25:27Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![bmeyers](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/bmeyers/32/37453_2.png) [@bmeyers](https://forum.inductiveautomation.com/u/bmeyers)\ **Post date:** [August 22, 2020, 12:25am UTC](https://forum.inductiveautomation.com/t/solved-how-to-get-a-unique-list-from-a-bigger-list-of-lists-based-on-1-criteria/37987/1 "2020-08-22T00:25:27Z")
Good evening, I have an m by n table with a column called p. How can I get all 1 row per unique p value into a new table i by j? Example: ``` a b c p d 1 2 1 1 'aab' 1 1 1 2 'aac' 3 3 1 2 'aad' 3 2 2 3 'aag' ``` would become: ``` a b c p d 1 2 1 1 'aab' 1 1 1 2 'aac' 3 2 2 3 'aag' ``` I’ve broken down the first table into a list of lists but I can’t come up with a method for deleting the 3rd row in the table to get the new table. Any help is much appreciated. ---
**Author:** ![JordanCClark](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/jordancclark/32/83362_2.png) [@JordanCClark](https://forum.inductiveautomation.com/u/JordanCClark)\ **Post date:** [August 22, 2020, 3:02am UTC](https://forum.inductiveautomation.com/t/solved-how-to-get-a-unique-list-from-a-bigger-list-of-lists-based-on-1-criteria/37987/2 "2020-08-22T03:02:13Z")
```python listIn = [[1, 2, 1, 1, 'aab'], [1, 1, 1, 2, 'aac'], [3, 3, 1, 2, 'aad'], [3, 2, 2, 3, 'aag']] existsList =[] listOut =[] for row in listIn if row[3] not in existsList: existsList.append(row[3]) listOut.append(row) print listOut ``` ---
**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\ **Post date:** [August 22, 2020, 1:29pm UTC](https://forum.inductiveautomation.com/t/solved-how-to-get-a-unique-list-from-a-bigger-list-of-lists-based-on-1-criteria/37987/3 "2020-08-22T13:29:17Z")
If you are running with very large datasets, use a `set` or `dict` instead of a `list` for tracking existence. ---
**Author:** ![bmeyers](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/bmeyers/32/37453_2.png) [@bmeyers](https://forum.inductiveautomation.com/u/bmeyers)\ **Post date:** [August 22, 2020, 4:17pm UTC](https://forum.inductiveautomation.com/t/solved-how-to-get-a-unique-list-from-a-bigger-list-of-lists-based-on-1-criteria/37987/4 "2020-08-22T16:17:27Z")
``` output = [] seen = set() for keyID, line, verName, modelDescrip, menGrp, staNo, seq, workCell, t_Sec, mCode, description, key_Point, quality_Chk, partNo, partName, scan, scan_req, pic, videoFileName, userAck in tbl: if seq in seen: continue output.append([keyID, line, verName, modelDescrip, menGrp, staNo, seq, workCell, t_Sec, mCode, description, key_Point, quality_Chk, partNo, partName, scan, scan_req, pic, videoFileName, userAck]) seen.add(seq) ``` A user on Stackoverflow was able to come up with the above code but I like yours better and will probably implement it at some point this weekend. ---
**Author:** ![bmeyers](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/bmeyers/32/37453_2.png) [@bmeyers](https://forum.inductiveautomation.com/u/bmeyers)\ **Post date:** [August 22, 2020, 4:19pm UTC](https://forum.inductiveautomation.com/t/solved-how-to-get-a-unique-list-from-a-bigger-list-of-lists-based-on-1-criteria/37987/5 "2020-08-22T16:19:07Z")
At the end of the day I don’t think it will be ever going over 100 rows but there is no rule stating they can’t have 10k rows i guess. ---
**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\ **Post date:** [August 22, 2020, 7:37pm UTC](https://forum.inductiveautomation.com/t/solved-how-to-get-a-unique-list-from-a-bigger-list-of-lists-based-on-1-criteria/37987/6 "2020-08-22T19:37:02Z")
The code from Stackoverflow is using tuple unpacking to place the data into named variables. While handy if you have complex expressions to do, it is pointless in your case. I do like the use of continue for loop short-circuit and the use of the set. I would blend the two implementations. ---
**Author:** ![bmeyers](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/bmeyers/32/37453_2.png) [@bmeyers](https://forum.inductiveautomation.com/u/bmeyers)\ **Post date:** [August 24, 2020, 3:06pm UTC](https://forum.inductiveautomation.com/t/solved-how-to-get-a-unique-list-from-a-bigger-list-of-lists-based-on-1-criteria/37987/7 "2020-08-24T15:06:38Z")
Took me a while to understand what you meant about unpacking tuples but after reading about Python collections (arrays), Ignition Datasets, and Ignition PyDataSets I have a better understanding of how all the pieces fit together. Thanks for the insight. ``` output = [] seen = set() for row in tbl: if row['seq'] in seen: continue output.append(list(row)) seen.add(row['seq']) ```