I am trying to install Python 3.6-dev with this command:

sudo apt-get install python3.6-dev

but I'm getting this error:

E: Unable to locate package python3.6-dev
E: Couldn't find any package by glob 'python3.6-dev'
E: Couldn't find any package by regex 'python3.6-dev'

Can anyone help? Why am I getting this error and what is the correct way to install the package?

sudo add-apt-repository ppa:deadsnakes/ppa \
&& sudo apt update \
&& sudo apt install python3.6

Edit: The following PPA has been disabled, see discussion here and the new PPA here . So use the PPA mentioned above instead.

Original answer:

As mentioned by omajid the package is not availible in 16.04. But if you need it in 16.04 you can get it by adding for example the personal package repository of Felix Krull:

sudo add-apt-repository ppa:fkrull/deadsnakes