# Error when running experiment

**URL:** <https://discourse.psychopy.org/t/error-when-running-experiment/30567>\
**Category:** Builder\
**Created:** [August 26, 2022, 2:21pm UTC](https://discourse.psychopy.org/t/error-when-running-experiment/30567 "2022-08-26T14:21:56Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![electricwitch](https://avatars.discourse-cdn.com/v4/letter/e/94ad74/32.png) [@electricwitch](https://discourse.psychopy.org/u/electricwitch)\
**Post date:** [August 26, 2022, 2:21pm UTC](https://discourse.psychopy.org/t/error-when-running-experiment/30567/1 "2022-08-26T14:21:56Z")

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I have recently downloaded PsychoPy and am using for the first time. I created a very simple experiment and upon trying to run it I get the following error message:

Traceback (most recent call last):  
File “/Applications/PsychoPy.app/Contents/Resources/ **boot**.py”, line 197, in   
File “/Applications/PsychoPy.app/Contents/Resources/ **boot**.py”, line 166, in \_run  
File “/Applications/PsychoPy.app/Contents/Resources/psychopyApp.py”, line 102, in   
File “/Applications/PsychoPy.app/Contents/Resources/psychopyApp.py”, line 98, in main  
File “/Applications/PsychoPy.app/Contents/Resources/psychopyApp.py”, line 27, in start\_app  
AttributeError: ‘NoneType’ object has no attribute ‘MainLoop’

After this the application quits. Can anyone help?

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<div class="post-metadata">

**Author:** ![wakecarter](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.psychopy.org/wakecarter/32/5753_2.png) [@wakecarter](https://discourse.psychopy.org/u/wakecarter)\
**Post date:** [August 26, 2022, 9:00pm UTC](https://discourse.psychopy.org/t/error-when-running-experiment/30567/2 "2022-08-26T21:00:40Z")

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Does your experiment contain any loops? If not, try adding one around your first routine. It can have 1 repetition and no spreadsheet.

What version of PsychoPy are you using?