Installing New Version of Python on Debian Linux Server

Installing new version of python on Debian Linux server

I think you'd better to install with compiling python 2.7.8 in your home directory. That's definitely clear for the others. 'update-alternatives' command makes system default python version change.

In my case, I made hidden directory '.opt' on my account. Then downloaded and extracted source code from python.org (https://www.python.org/ftp/python/2.7.8/Python-2.7.8.tgz) with below command.

$ cd $HOME
$ mkdir -p .opt
$ wget https://www.python.org/ftp/python/2.7.8/Python-2.7.8.tgz
$ tar zxvf Python-2.7.8.tgz

It'll make Python-2.7.8 directory on your account home. So change directory Python-2.7.8.

$ cd Python-2.7.8

Please configure with 'prefix' option. In my case '--prefix=$HOME/.opt'.

$ ./configure --prefix=$HOME/.opt

It'll be configured with setting at your home directory. After than you can 'make' and 'make install'.

$ make && make install

If there are no errors, you can find directories for python binaries in .opt directory. $HOME/.opt/bin/python is new one. Please set path environment variable in your profile in .bashrc or .profile.

$ echo "export PATH=$HOME/.opt/bin:$PATH" >> $HOME/.bashrc

It'll be works only for your account.

How can I upgrade python on a Debian server?

You could also compile the latest source and install Python to an alternative path from the default (so that applications don't get messed up). Basically you would download the latest Python, configure it, compile, then install.

$> wget https://www.python.org/ftp/python/2.7.11/Python-2.7.11.tgz
$> tar xvhf Python-2.7.11.tgz
$> cd Python-2.7.11
$> ./configure
$> make
$> sudo make altinstall

Update

To see all the available options for Python configuration execute ./config --help. This is important to know because, by default, many options are left out (especially in Python 2.x) such as unicode or IPv6 support. Features can also be disabled if required.

Reference

• Installing new version of python on Debian Linux server
• Building Python from source on Debian or Ubuntu

How to install python 3.4.3 from source and pip on Debian

Add the line in which you export the PATH variable to the .profile and it will work after logging back in.

You can do this by executing

echo 'export PATH="$PATH:/opt/python3.4.3/bin"' >> ~/.profile

Instead of changing the PATH variable, you could simply install python into the system directories (where it is better placed), by going to the root of the source directory and running

./configure
make
sudo make install

If pip is distributed within the python source, then it will be installed, too. Check if pip has been installed by executing

pip --version

If it is not, you have to manually install pip, too.

https://pip.pypa.io/en/latest/installing.html explains how this is done.
Simply download the script get-pip.py and run it like this

sudo python get-pip.py

How do I downgrade my version of python from 3.7.5 to 3.6.5 on ubuntu

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 <command> [<args>]

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 <command>' for information on a specific command.
For full documentation, see: https://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

Multiple Python versions on the same machine?

I think it is totally independent. Just install them, then you have the commands e.g. /usr/bin/python2.5 and /usr/bin/python2.6. Link /usr/bin/python to the one you want to use as default.

All the libraries are in separate folders (named after the version) anyway.

If you want to compile the versions manually, this is from the readme file of the Python source code:

Installing multiple versions

On Unix and Mac systems if you intend to install multiple versions of Python
using the same installation prefix (--prefix argument to the configure
script) you must take care that your primary python executable is not
overwritten by the installation of a different version. All files and
directories installed using "make altinstall" contain the major and minor
version and can thus live side-by-side. "make install" also creates
${prefix}/bin/python3 which refers to ${prefix}/bin/pythonX.Y. If you intend
to install multiple versions using the same prefix you must decide which
version (if any) is your "primary" version. Install that version using
"make install". Install all other versions using "make altinstall".

For example, if you want to install Python 2.5, 2.6 and 3.0 with 2.6 being
the primary version, you would execute "make install" in your 2.6 build
directory and "make altinstall" in the others.

How do I update a Python package?

You might want to look into a Python package manager like pip. If you don't want to use a Python package manager, you should be able to download M2Crypto and build/compile/install over the old installation.

Unable to set default python version to python3 in ubuntu

EDIT:

I wrote this when I was young and naive, update-alternatives is the better way to do this. See @Pardhu's answer.

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Outdated answer:

Open your .bashrc file nano ~/.bashrc. Type alias python=python3
on to a new line at the top of the file then save the file with ctrl+o
and close the file with ctrl+x. Then, back at your command line type
source ~/.bashrc. Now your alias should be permanent.

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