# Unicorn hat - fatal error

**URL:** <https://forums.pimoroni.com/t/unicorn-hat-fatal-error/4311>\
**Category:** Support\
**Created:** [March 16, 2017, 2:45am UTC](https://forums.pimoroni.com/t/unicorn-hat-fatal-error/4311 "2017-03-16T02:45:41Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![jonathanhoff](https://sea2.discourse-cdn.com/flex016/user_avatar/forums.pimoroni.com/jonathanhoff/32/405_2.png) [@jonathanhoff](https://forums.pimoroni.com/u/jonathanhoff)\
**Post date:** [March 16, 2017, 2:45am UTC](https://forums.pimoroni.com/t/unicorn-hat-fatal-error/4311/1 "2017-03-16T02:45:41Z")

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My unicorn hat was working fine until the other day when somehow the OS was reinstalled and everything I had set up overwritten

Now when running the bash command to install everything for unicorn hat I am getting the following:

rpi\_ws281x\_wrap.c:130:21: fatal error: Python.h: No such file or directory

# include \<Python.h\>

compilation terminated.

error: comman ‘arm-linux-gnueabihf-gcc’ failed with exit status 1

Getting this after sudo apt-get update/upgrade

Why??!!

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**Author:** ![RogueM](https://sea2.discourse-cdn.com/flex016/user_avatar/forums.pimoroni.com/roguem/32/311_2.png) [@RogueM](https://forums.pimoroni.com/u/RogueM)\
**Post date:** [March 16, 2017, 9:36am UTC](https://forums.pimoroni.com/t/unicorn-hat-fatal-error/4311/2 "2017-03-16T09:36:55Z")

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the best way to install our libraries is via the one-line installer… but if you want to go down the manual route, then knowing that `Python.h` is a header provided by the `python-dev` package may be useful.

… so `sudo apt-get install python-dev python3-dev` will help.

well, or use the method recommended in the github and live without having to read the small prints ;-)