Usage of Python
=================================


About using Python
------------------------------------

In this system, pyenv can be installed in the user's environment by executing the following script. Python version control is possible with pyenv. Please see below for details.


Install pyenv
------------------------------------

Execute the following command to install pyenv on super and gpu.

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   bash /work/app/pyenv/pyenv-setup.bash

Backing up the pyenv environment from the previous system
------------------------------------------------------------------------

If you used the pyenv environment in the previous system, you will need to back up the old pyenv environment.
Please back up the old environment with the command below.

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   mv ~/.pyenv-super ~/.pyenv-super.old
   mv ~/.pyenv-gpu ~/.pyenv-gpu.old



Setting environment variables
------------------------------------

The pyenv environment variable file is located in /work/app/pyenv/bash_env.
If you want to load the pyenv environment by default, run the command below.


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   echo "source /work/app/pyenv/bash_env" >> ~/.bash_profile


Operational check
------------------------------------

After installing pyenv, log out from the front end node once, log in again, and then execute the following command.

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   pyenv --version 
   pyenv 1.2.8-5-gec9fb549   ←The version may be different.
   

Basic usage
------------------------------------

・Install Python using pyenv 

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   pyenv install --list    ←View available Python versions 
   ・・・・ 
   pyenv install 3.7.8     ←Install Python 3.7.8


・Switch python versions

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   pyenv versions      ←Check the installed version
   * system (set by /home/userA/.pyenv/version) 
   3.7.8 
   pyenv global 3.7.8  ←Switch to Python 3.7.8 
   python --version

You can also add packages using pip.
For more detailed usage, please check the pyenv documentation etc.

`Simple Python version management <https://github.com/pyenv/pyenv>`_ 


Execution method
------------------------------------

Execute Python programs with high load on compute nodes instead of front end nodes.


・A example for interactive mode

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   userA@gpu2:~> qsub -I -q IP_001
   qsub: waiting for job 70568.gpu1 to start 
   qsub: job 70568.gpu1 ready
   -bash-4.2$ python 
   Python 3.7.8 (default, Mar 25 2021, 09:54:46)  
   [GCC 4.8.5 20150623 (Red Hat 4.8.5-28)] on linux 
   Type "help", "copyright", "credits" or "license" for more 
   information. 
   >>>

You may also execute as a job script.


・A example for job script

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   #!/bin/sh 
   #PBS -l select=1 
   #PBS -q CA_001 
   #PBS -N sample 
 
   cd $PBS_O_WORKDIR

   python program.py