# Dataset : Basic Python

**URL:** <https://forum.inductiveautomation.com/t/dataset-basic-python/40093>\
**Category:** Ignition\
**Tags:** ignition80\
**Created:** [October 28, 2020, 2:10pm UTC](https://forum.inductiveautomation.com/t/dataset-basic-python/40093 "2020-10-28T14:10:07Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![kaushik.shah](https://avatars.discourse-cdn.com/v4/letter/k/34f0e0/32.png) [@kaushik.shah](https://forum.inductiveautomation.com/u/kaushik.shah)\
**Post date:** [October 28, 2020, 2:10pm UTC](https://forum.inductiveautomation.com/t/dataset-basic-python/40093/1 "2020-10-28T14:10:07Z")

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Hello There,  
I am seeing something very strange here.

 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/d/c/dc35d605217c6e25a727a1ea652194993ad61cb9.png)

Just trying to create new dataset with basic scripting but dont know why the data list is altering first element automatically.

Please look at the list at the end of each loop and then final nested lists. First element of nested list is altered automatically.  
Any idea ?

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**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\
**Post date:** [October 28, 2020, 2:19pm UTC](https://forum.inductiveautomation.com/t/dataset-basic-python/40093/2 "2020-10-28T14:19:06Z")

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You are mutating the row/list you added to `data` in place.

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<div class="post-metadata">

**Author:** ![kaushik.shah](https://avatars.discourse-cdn.com/v4/letter/k/34f0e0/32.png) [@kaushik.shah](https://forum.inductiveautomation.com/u/kaushik.shah)\
**Post date:** [October 28, 2020, 2:36pm UTC](https://forum.inductiveautomation.com/t/dataset-basic-python/40093/3 "2020-10-28T14:36:20Z")

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Got it ! Thanks