PyEnv
PyEnv is similar to rbenv and allows to use multiple Python versions simultenously. It means it is able to bind an installed script with proper virtualenv and appropriate python version. It integrates well with virtualenv. Really cool stuff.
Below are procedures to install Python 3.6 and 3.7 for Ubuntu and RHEL. I have tested them with Ubuntu 20-22 and RHEL7.
Pre requisites
pyenv downloads and compiles Python. There is a list of dependencies
which are required in the system before using pyenv to compile the Python
installation. Most of packages have been listed below but if something is
missing you can find it on Google.
# RHEL
yum install -y zlib-dev openssl-devel sqlite-devel bzip2-devel \
readline-devel libffi-devel tk-devel curl git
# or
dnf install zlib-devel bzip2 bzip2-devel readline-devel sqlite \
sqlite-devel openssl-devel xz xz-devel
# UBuntu 22
apt install -y make build-essential libssl-dev zlib1g-dev \
libreadline-dev tk-dev \
libsqlite3-dev sqlite3 \
libncurses5-dev libncursesw5-dev \
xz-utils liblzma-dev bzip2 libbz2-dev libz-dev \
tk-dev curl wget llvm git
# install then follow onscreen instructions to modify
# rc files
curl -L https://raw.githubusercontent.com/yyuu/pyenv-installer/master/bin/pyenv-installer | bash
At least for Ubuntu16 I hit a weird problem with libreadline being not
properly installed and not recognized by python installator. In such the
case you may try to uninstall the metapackage and install specifically
its 6 version:
apt remove libreadline-dev libreadline6-dev
apt install libreadline6-dev
More details on that may be found in pyenv issue #1479.
Installing Python with pyenv
pyenv install -l
pyenv install 3.6.4
pyenv install 3.7.2
pyenv version
pyenv global 3.6.4 3.7.2 system
pyenv version
If something goes wrong, uninstall the failed version
(eg. pyenv uninstall 3.6.4), correct and retry.
Always install virtualenv within the new python version you have created. You will need virtualenv later:
pip install virtualenv
pyenv activate 3.7.2
pip install virtualenv
Creating Own VirtualEnv with pyenv
Assume I want to open a new project named rdspump to work with python 3.7.2:
pyenv virtualenv 3.7.2 rdspumptest
pyenv activate rdspumptest
pip install cx_Oracle
pip install rdspump
pyenv deactivate
The pyenv virtualenv creates new virtualenv with the python version 3.7.2.
Then pyenv activate fixes the current environment to newly created virtualenv
rdspump. And the following pip install commands affect only rdspumptest virtualenv.
The current virtualenv needs to be deactivated afterwards.
Then when I try to call newly created rdspump I get in response:
$ rdspump
pyenv: rdspump: command not found
The `rdspump' command exists in these Python versions:
3.7.2/envs/rdspumptest
rdspumptest
$
My pyenv says it has rdspump in the rdspumptest virtualenv but
it won’t be called because it is not in the path. I can either
add it to the global path or call pyenv activate rdspumptest before using
rdspump command:
$ pyenv global 3.6.4 3.7.2 rdspumptest system
$ rdspump
At least one argument expected.
usage: rdspump [-h] [-l [LIST_PROFILES]] [-P PROFILE] [--version]
{get,put,del} ...
$
This time rdspump has been found in the rdspumptest virtualenv during scanning
pyenv global path. Awesome.
There is in-depth analysis of pyenv/virtualenv/virtualenvwrapper configuration on this blog blost: “The Definitive Guide to Setup My Python Workspace”.
The command pyenv global precendence_list is worth some explanation:
It set up search path for python programs. Say you have installed youtube-dl
in 3.7.2. If you call it with python youtuble-dl the python version used will
be
Updating pyenv
Pyenv does not update itself, the list of available python versions is the same until pyenv is updated. Pyenv can be updated anytime using git.
cd $(pyenv root)
git pull
pyenv install -l