Downgrade python 3.9 to 3.7 ubuntu

I need to change my python version from 3.8 to 3.6 ? How can I achieve this in Ubuntu 20.04. I tried pyenv, but when I try to use pyenv like pyenv global 3.6.0 then I do python3 and I have still 3.8 verision.

asked Nov 3, 2021 at 18:41

Do not downgrade the system version: it's likely that some parts of the system would stop working. Never change /usr/bin/python3, and avoid putting an older version of python3 before it in the $PATH.

The deadsnakes archive provides packages of most supported Python versions for currently supported Ubuntu LTS versions. To make these packages available, follow the usual instructions to enable a PPA. Then install the package[s] you want.

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

You can then create a virtual environment for your chosen Python version and with a chosen set of packages.

python3.6 -m venv ~/python/foo-3.6
sh -c '.export PYTHONNOUSERSITE=1;  ~/python/foo-3.6/bin/activate; pip install …'

To run a program in this environment, source the bin/activate script in a shell.

$ bash
$ export PYTHONNOUSERSITE=1
$ . ~/python/foo-3.6/bin/activate
$ ./my_python_program

answered Nov 3, 2021 at 19:11

Alternatively, you can create a virtual environment.

Suppose you have python 3.8 [or higher] installed on the system, but for a specific task, you need python 3.7 [or lower]. The best idea is [not to downgrade] to Create a virtual environment with python 3.7[or any 3.x, change the commands below according to your desired version. Below is an implementation of a virtual environment with python 3.7]

Steps: [Checked August 2022]

Install python 3.7 and it’s virtual environment packages.
sudo apt-get install python3.7-dev python3.7-venv
Find out where your python 3.7 is located by this command:

which python3.7 [Should be something like /usr/bin/python3.7, if not found, then install python 3.7 manually]
Create Virtual Environment in the Home directory.
cd
mkdir virtual_env
/usr/bin/python3.7 -m venv ~/virtual_env/venv_with_python3.7
source ~/virtual_env/venv_with_python3.7/bin/activate
python --version [Should be python 3.7 now]
Done. Python 3.7 can be used in this virtual environment. Type which python, you’ll see you have created python 3.7 in a virtual environment, rather than in the system globally.
Run deactivate when you need to deactivate.

answered Aug 19 at 9:16

The following talks about upgrade from 3.6.7 to 3.7.0 but you can use the same process for downgrade. You should not change the system python unless you really know what you're doing

First Install Pyenv

Installlation Instructions are here

Look at Pyenv Options

$ pyenv 
pyenv 1.2.14
Usage: pyenv  []

Some useful pyenv commands are:
   commands    List all available pyenv commands
   activate    Activate virtual environment
   commands    List all available pyenv commands
   deactivate   Deactivate virtual environment
   doctor      Verify pyenv installation and deevlopment tools to build pythons.
   exec        Run an executable with the selected Python version
   global      Set or show the global Python version
   help        Display help for a command
   hooks       List hook scripts for a given pyenv command
   init        Configure the shell environment for pyenv
   install     Install a Python version using python-build
   local       Set or show the local application-specific Python version
   prefix      Display prefix for a Python version
   rehash      Rehash pyenv shims [run this after installing executables]
   root        Display the root directory where versions and shims are kept
   shell       Set or show the shell-specific Python version
   shims       List existing pyenv shims
   uninstall   Uninstall a specific Python version
   --version   Display the version of pyenv
   version     Show the current Python version and its origin
   version-file   Detect the file that sets the current pyenv version
   version-name   Show the current Python version
   version-origin   Explain how the current Python version is set
   versions    List all Python versions available to pyenv
   virtualenv   Create a Python virtualenv using the pyenv-virtualenv plugin
   virtualenv-delete   Uninstall a specific Python virtualenv
   virtualenv-init   Configure the shell environment for pyenv-virtualenv
   virtualenv-prefix   Display real_prefix for a Python virtualenv version
   virtualenvs   List all Python virtualenvs found in `$PYENV_ROOT/versions/*'.
   whence      List all Python versions that contain the given executable
   which       Display the full path to an executable

See `pyenv help ' for information on a specific command.
For full documentation, see: //github.com/pyenv/pyenv#readme

Look at Python Versions

$ pyenv versions
  system
 * 3.6.7 [set by /home/taarimalta/.pyenv/version]

Install a new Python

$ pyenv install 3.7.0
Installing Python-3.7.0...
WARNING: The Python bz2 extension was not compiled. Missing the bzip2 lib?
WARNING: The Python readline extension was not compiled. Missing the GNU readline lib?
WARNING: The Python sqlite3 extension was not compiled. Missing the SQLite3 lib?
Installed Python-3.7.0 to /home/taarimalta/.pyenv/versions/3.7.0

If you run into an issue with _ctypes install libffi-dev library

Now look at the versions


$ pyenv versions
  system
* 3.6.7 [set by /home/taarimalta/.pyenv/version]
  3.7.0

Select 3.7.0 for local environment

$ pyenv local 3.7.0

See that the version changed

$ pyenv versions
  system
  3.6.7
 * 3.7.0 [set by /home/taarimalta/.python-version]

$ python
Python 3.7.0 [default, Jan  1 2020, 10:52:57] 
[GCC 9.2.1 20191008] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>

Switch to a different folder

cd ../project2
pyenv versions
  system
* 3.6.7 [set by /home/taarimalta/.pyenv/version]
  3.7.0

The python version may be different here depending on which python version you have set locally

Set pyenv version globally

This globally sets a python version for a user

pyenv global 3.7.0

Note that pyenv sets local version by adding a .python-version file

$ pyenv local 3.7.0
$ cat .python-version
3.7.0

Note that pyenv knows the global version by looking at the ~/.pyenv/version file

cat ~/.pyenv/version
3.8.2

How do I downgrade from Python 3.9 to 3.8 Ubuntu?

Downgrade Python 3.9 to 3.8 With the virtualenv Module.

Copy virtualenv \path\to\env -p \path\to\python_install. exe..

Copy \path\to\env\Scripts\activate. bat..

Copy conda create -n downgrade python=3.8 anaconda..

How do I change Python to 3.7 in Ubuntu?

I have followed the below steps to upgrade from 3.5 to 3.7..

Step 1: Check the current version. $ python3 --version. ... .

Step 2: Update Ubuntu packages. sudo apt-get update..

Step 3: Install python3. ... .

Step 4: Update python 3 to point to python 3.7..

How do I switch from Python 3.8 to 3.7 Ubuntu?

“downgrade python 3.8 to 3.7 ubuntu” Code Answer.

sudo add-apt-repository ppa:deadsnakes/ppa..

sudo apt-get update..

sudo apt-get install python3.7..

How do I downgrade Python version from terminal?

Use a Virtual Environment to Downgrade Python on Windows To create a virtual environment, we can use the command pip install virtualenv on the command prompt. We need to download the required version from the official website. After this, we need to execute virtualenv \pathof\the\env -p \pathof\the\python_install.exe .