I would recommend pyenv to solve your woes. It doesn't use Aptitude, and does involve "building it yourself", but it's fully automated. You can build and install a new (or old) version of Python by simply saying pyenv install 3.6.0. Everything runs as your user, so you don't have to worry about messing up the Python used by Ubuntu itself.

Plus, the answer to the follow-up question "How do I install Python 3.7 using apt-get?" has the same answer: pyenv update; pyenv install 3.7.0. It will generally work same day of a release because you don't need to wait for someone else to package it for Ubuntu. See all the versions you can install with pyenv install --list

Install pyenv

1. 
   

   Install tools and headers needed to build CPythons (exotic Pythons like PyPy or Jython may have other dependencies). Git is used by pyenv, plus it also enables builds/installs of source branches, so you could install whatever 3.8 is right now, i.e. the master branch of CPython fresh off GitHub:

   
   
   

   sudo apt-get install -y git
   
   sudo apt-get install -y build-essential libbz2-dev libssl-dev libreadline-dev 
   
                           libffi-dev libsqlite3-dev tk-dev
   
   
   
   # optional scientific package headers (for Numpy, Matplotlib, SciPy, etc.)
   
   sudo apt-get install -y libpng-dev libfreetype6-dev    
   
   

   
   


2. 
   

   Run the installer script (installs pyenv and some very useful pyenv plugins by the original author; see here for more)

   
   
   

   curl -L https://github.com/pyenv/pyenv-installer/raw/master/bin/pyenv-installer | bash
   
   

   
   


3. 
   

   Add init lines to your ~/.profile or ~/.bashrc (it mentions it at the end of the install script):

   
   
   

   export PATH="~/.pyenv/bin:$PATH"
   
   eval "$(pyenv init -)"
   
   eval "$(pyenv virtualenv-init -)"
   
   

   
   



4. Restart your shell (close & open or exec $SHELL) or reload the profile script. (with e.g. source ~/.bashrc)

Done!

Setting up an environment

To not touch the system Python (generally a bad idea; OS-level services might be relying on some specific library versions, etc.) make your own environment, it's easy! Even better, no sudo, for it or pip installs!

1. 
   

   Install your preferred Python version (this will download the source and build it for your user, no input required)

   
   
   

   pyenv install 3.6.0
   
   

   
   


2. 
   

   Make it a virtualenv so you can make others later if you want

   
   
   

   pyenv virtualenv 3.6.0 general
   
   

   
   


3. 
   

   Make it globally active (for your user)

   
   
   

   pyenv global general
   
   

   
   



4. Do what you want to with the Python/pip, etc. It's yours.

If you want to clean out your libraries later, you could delete the virtualenv (pyenv uninstall general) or make a new one (pyenv virtualenv 3.6.0 other_proj). You can also have environments active per-directory: pyenv local other_proj will drop a .python-version file into your current folder and any time you invoke Python or pip-installed Python utilities from it or under it, they will be shimmed by pyenv.

Troubleshooting

• 
  

  bash: pyenv: command not found, fish: Unknown command 'pyenv'

  
  
  
  
  
  1. Check your $PATH, there should be one entry that ends in something like .pyenv/bin. If it's missing make sure you followed #3 AND #4 (restart your shell) under Install pyenv above.
  
  
  
  


• 
  

  pyenv: no such command 'virtualenv'

  
  
  
  
  
  1. If you didn't use the installer script, you likely only installed the root pyenv package. See pyenv-virtualenv for instructions to add the plugin
  
  
  2. If you used the installer script, check if it shows up with pyenv commands.
  
  
  
  

An alternative route if you can't find any working repos would be you could try compiling yourself from source. You can find the source code on the download page. Then download and untar the tarball; for example for Python-3.6.1.tgz.

The process for untarring the tgz file is:

tar -xvzf /path/to/yourfile.tgz

Once you are in the file path the file was unzipped to, run:

./configure

make

make altinstall

And hopefully this should solve the problem for you.

It depends on which version of Ubuntu you are using.

Ubuntu 16.10 and Ubuntu 17.04

Since Python 3.6 is installed in the universe repository of Ubuntu 16.10 and Ubuntu 17.04, you can directly install python 3.6 from the repository. Just use the commands below:

sudo apt update

sudo apt install python3.6

Ubuntu 16.04

There are two ways to install Python3.6 on Ubuntu 16.04

• Compile and install python 3.6 on Ubuntu 16.04


• Install python 3.6 on Ubuntu 16.04 from PPA

1. Compile and install python 3.6 on Ubuntu 16.04

Install the necessary dependencies, download the python 3.6 source code, and build the environment and install

sudo apt install build-essential checkinstall

sudo apt install libreadline-gplv2-dev libncursesw5-dev libssl-dev libsqlite3-dev tk-dev libgdbm-dev libc6-dev libbz2-dev

wget https://www.python.org/ftp/python/3.6.0/Python-3.6.0.tar.xz

tar xvf Python-3.6.0.tar.xz

cd Python-3.6.0/

./configure

sudo make altinstall

2. Install python 3.6 on Ubuntu 16.04 from PPA

You can install Python 3.6  from PPA using the commands below

sudo add-apt-repository ppa:jonathonf/python-3.6

sudo apt update

sudo apt install python3.6

If Python 3.6 is correctly installed, you can invoke the python interpreter by running python3.6 in the terminal.

I hope this helps. If you are having any issues, you can check this blog post here.

For Ubuntu 15.10 I installed it successfully using this method:

sudo add-apt-repository ppa:jonathonf/python-3.6

But I edited this file:

sudo vi /etc/apt/sources.list.d/jonathonf-ubuntu-python-3_6-wily.list

And I changed wily to trusty and then:

sudo apt-get update

sudo apt-get install python3.6

Consider pyenv + pipenv which is to replace using PIP + virtual environments using Pipfile

Then in Pipfile

[requires]

python_version = "3.6"

https://stackoverflow.com/a/49800061/1689770

First, follow some of the other answers to install Python 3.6 or 3.7. Then, if want to install PyPi packages such as OpenEXR through pip you may get some errors. Some of them (e.g. for OpenEXR's PyPi package) might get resolved by installing Python development package for your newly-installed Python. This can be done using the followings:

sudo apt-get install python3.6-dev

or

sudo apt-get install python3.7-dev

Perhaps suggesting Conda isn't a bad idea. I think it's at least easier than using pyenv. But maybe it does depend on what you intend to do with Python after all, because I think with Conda you may end up with some extra packages.

EDIT: It's probably worth mentioning that after you install Conda's default version of Python, you can install the version you need, here 3.6, using conda like

conda install python==3.6