How to install Python 3.6 on Ubuntu 19.04?

Question

I've recently installed Ubuntu 19.04 which has Python 3.7 by default. I need to work on multiple projects that use Python 3.6.

Is there a way to install it on Disco Dingo?

I tried which works on 16.04

milano@milano-desktop:~$ sudo add-apt-repository ppa:jonathonf/python-3.6
...
milano@milano-desktop:~$ sudo apt-get install python3.6
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Note, selecting 'python3.6-2to3' for regex 'python3.6'
Note, selecting 'libpython3.6-stdlib' for regex 'python3.6'
The following packages were automatically installed and are no longer required:
  fonts-liberation2 fonts-opensymbol gir1.2-geocodeglib-1.0
  gir1.2-gst-plugins-base-1.0 gir1.2-gstreamer-1.0 gir1.2-gudev-1.0
  gir1.2-udisks-2.0 grilo-plugins-0.3-base gstreamer1.0-gtk3 guile-2.2-libs
  libboost-date-time1.67.0 libboost-filesystem1.67.0 libboost-iostreams1.67.0
  libboost-locale1.67.0 libcdr-0.1-1 libclucene-contribs1v5 libclucene-core1v5
  libcmis-0.5-5v5 libcolamd2 libcurl4 libdazzle-1.0-0 libe-book-0.1-1 libeot0
  libepubgen-0.1-1 libetonyek-0.1-1 libevent-2.1-6 libfreerdp-client2-2
  libfreerdp2-2 libgc1c2 libgee-0.8-2 libgom-1.0-0 libgpgmepp6 libgpod-common
  libgpod4 liblangtag-common liblangtag1 liblirc-client0 liblua5.3-0
  libmediaart-2.0-0 libminiupnpc17 libmspub-0.1-1 libodfgen-0.1-1
  liborcus-0.14-0 libqqwing2v5 libraw19 librevenge-0.0-0 libsgutils2-2
  libsuitesparseconfig5 libvncclient1 libwinpr2-2 libxmlsec1 libxmlsec1-nss
  lp-solve media-player-info python3-mako python3-markupsafe syslinux
  syslinux-common syslinux-legacy usb-creator-common
Use 'sudo apt autoremove' to remove them.
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
milano@milano-desktop:~$ python3.6

Command 'python3.6' not found, did you mean:

  command 'python3.8' from deb python3.8-minimal (3.8.0~a3-2)
  command 'python3.7' from deb python3.7-minimal (3.7.3-2)

Try: sudo apt install <deb name>

python3 + tab

milano@milano-desktop:~$ python3
python3     python3.7   python3.7m  python3m 

deadsnakes

milano@milano-desktop:~$ sudo add-apt-repository ppa:deadsnakes/ppa
 This PPA contains more recent Python versions packaged for Ubuntu.

Disclaimer: there's no guarantee of timely updates in case of security problems or other issues. If you want to use them in a security-or-otherwise-critical environment (say, on a production server), you do so at your own risk.

Update Note
===========
Please use this repository instead of ppa:fkrull/deadsnakes.

Reporting Issues
================
Issues can be reported in the master issue tracker at:
https://github.com/deadsnakes/issues/issues

Supported Ubuntu and Python Versions
====================================
Python 3.6 - Ubuntu 14.04, Ubuntu 16.04

For Ubuntu up to 18.04, there's also packages for old Python versions from 2.3 to 3.4.

The packages may also work on other versions of Ubuntu or Debian, but that is not tested or supported.

Third-Party Python Modules
==========================
Python modules in the official Ubuntu repositories are packaged to work with the Python interpreters from the official repositories. Accordingly, they generally won't work with the Python interpreters from this PPA. As an exception, pure-Python modules for Python 3 will work, but any compiled extension modules won't.

To install 3rd-party Python modules, you should use the common Python packaging tools.  For an introduction into the Python packaging ecosystem and its tools, refer to the Python Packaging User Guide:
https://packaging.python.org/installing/

Sources
=======
The package sources are available at:
https://github.com/deadsnakes/
 More info: https://launchpad.net/~deadsnakes/+archive/ubuntu/ppa
Press [ENTER] to continue or Ctrl-c to cancel adding it.

Hit:1 http://cz.archive.ubuntu.com/ubuntu disco InRelease
Ign:2 http://ppa.launchpad.net/deadsnakes/ppa/ubuntu disco InRelease           
Get:3 http://cz.archive.ubuntu.com/ubuntu disco-updates InRelease [88,4 kB]    
Hit:4 http://security.ubuntu.com/ubuntu disco-security InRelease               
Hit:5 http://cz.archive.ubuntu.com/ubuntu disco-backports InRelease            
Ign:6 http://ppa.launchpad.net/jonathonf/python-3.6/ubuntu disco InRelease
Err:7 http://ppa.launchpad.net/deadsnakes/ppa/ubuntu disco Release
  404  Not Found [IP: 91.189.95.83 80]
Err:8 http://ppa.launchpad.net/jonathonf/python-3.6/ubuntu disco Release
  404  Not Found [IP: 91.189.95.83 80]
Reading package lists... Done                      
E: The repository 'http://ppa.launchpad.net/deadsnakes/ppa/ubuntu disco Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The repository 'http://ppa.launchpad.net/jonathonf/python-3.6/ubuntu disco Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

Answer 1

Don't mess around in your system.

Ubuntu 19.04 as Python 3.7 as given standard so if you want to work with Python 3.6.*, you should install conda and create an environment with the specific Python version:

conda create --name py36 -c conda-forge python=3.6.* pip  

For sure you could also create an other virtual environment and use pip.

Or you could go to docker.

---

On Linux / macOS you could use nix like

nix-env -iA nixpkgs.python37

to enter an environment that has e.g. in this case Python3.7 (for sure you can change the version)

or as a very good Python (advanced) environment you can use mach-nix (with nix) like

mach-nix env ./env -r requirements.txt 

(which even supports conda [but currently in beta])

or via api like

nix-shell -p nixFlakes --run "nix run github:davhau/mach-nix#with.ipython.pandas.seaborn.bokeh.scikit-learn "

---

If you really want to change the version on the operating system then I would recommend to use NixOS.

Answer 2

Yes as @furas says you can download the source of python 3.6.8 or 3.6.7 (these are direct link of .xz source files if you want in another format, visit 3.6.8 or 3.6.7)

these are some contents from the README.rst file of the source

Build Instructions
------------------

On Unix, Linux, BSD, macOS, and Cygwin::

    ./configure
    make
    make test
    sudo make install

This will install Python as python3.

If you want python3.6 install as python3.6(not python3) in your system here are some other guide lines in README.rst file

For example, if you want to install Python 2.7, 3.5, and 3.6 with 3.6 being the
primary version, you would execute ``make install`` in your 3.6 build directory
and ``make altinstall`` in the others.

Thanks...