==== Python Virtual Environments ====

[[https://towardsdatascience.com/a-guide-to-conda-environments-bc6180fc533#7d04|Overview to conda environments]]

__Installing miniconda__

  * Download and install miniconda3 as non-admin user from https://docs.conda.io/en/latest/miniconda.html
  * Get the "Miniconda3 Linux 64-bit" version
  * NOTE: You may need to remove a $HOME/.condarc file if you have one to prevent repo source conflicts

  cd $HOME
  mkdir $HOME/tmpconda
  TMPDIR=$HOME/tmpconda
  wget https://repo.anaconda.com/miniconda/Miniconda3-latest-Linux-x86_64.sh
  TMPDIR=$HOME/tmpconda bash Miniconda3-latest-Linux-x86_64.sh

  * (Accept license agreement and all the suggested default choices)
  * Note that if you do not want conda's base environment to be activated upon startup, run the following:

  conda config --set auto_activate_base false

Now try creating a test conda environment:

  cd ~/miniconda3/envs
  ~/miniconda3/bin/conda create -n testenv2_3.11.4 -c conda-forge time numpy requests pygrib netCDF4 scipy python=3.11.4
  ~/miniconda3/bin/conda init bash

  * (Open a new xterm and type 'bash')

  conda activate $HOME/miniconda3/envs/testenv
  cd $HOME/miniconda3/envs/testenv

  * (do work)

  conda deactivate
  
Other useful commmands (see https://www.python.org/downloads/ for specific python versions) :
  conda create -n testenv2 python=3.11.3
  conda activate testenv2
  
  conda update conda (update just the conda package)
  conda update --all (update all conda packages)
  python3 -m pip list --outdated
  python3 -m pip install --upgrade <package_name>
  
  conda install conda=23.3.1 (installing or force-installing a specific conda package version)
  
  conda -V (the conda version)
  
  conda remove --name myenv --all (remove a conda environment)

__Running a cron under conda (is this correct?)__
  21 15 * * * conda activate testenv2; /path/to/script.py > /tmp/output.txt (just call the correct version of python in first line of the script)

Questions/Tests:
  * Create a conda test env with specific version of python
  * Run a script using that new test environment
    * Update the first line to point to the correct version of python
  * Run cron under conda
    * If you update the first line in the script to point to desired conda version of python, then no need to activate the conda env (?)

__Using venv to set up a python virtual environment__

<color #ed1c24>Note: This method __does not__ allow for running a different version of python that is natively installed on the system.</color>

  python3 -m venv venv_test
  source venv_test/bin/activate
  cd venv_test
  pip list
  pip install --upgrade pip
  pip install pygrib
  
  (venv_test) (base) [user@host: ~/venv_test]$ pip list
  Package    Version
  ---------- ---------
  certifi    2022.6.15
  numpy      1.21.6
  pip        22.1.2
  pygrib     2.1.4
  pyproj     3.2.1
  setuptools 40.6.2
  
When done working:
  deactivate
  
__Setting up a python virtual environment (with virtualenv)__

<color #ed1c24>Note: This method __does__ allow for running a different version of python that is natively installed on the system.</color>

  dnf install virtualenv
  virtualenv --python="/usr/local/bin/python" "/path/to/the/venv_dir/"
  cd /path/to/the/venv_dir
  source bin/activate
  
See [[python_alternative_upgrade_notes|Python Alternative Upgrade Notes]] for installing a different/local version of python.