[Tutor] Python installtion

[Stephen Nelson-Smith]

Hi,

On Mon, Jan 7, 2019 at 11:11 AM mousumi sahu
<mousumi.nina.sahu1 at gmail.com> wrote:
>
> Dear Sir,
> I am trying to install python 2.7.10 on HPC. Python 2.6 has already been
> install on root. I do not have root authority. Please suggest me how can I
> do this.

Sorry - I replied to you directly, by accident.  Take 2, with reply all:

You need to do a local installation of Python, and set up your system
to use that in preference to the one at the system level.  Although
it's possible to do this with various manual steps, there's a really
handy tool you can use which will make your life easier, and allow you
to manage multiple versions of Python, which might be useful, if you
wanted, say, to be able to run both Python 2 and Python 3.  The tool
is called `pyenv`, and as long as you have a bash/zsh shell, and your
system has a C compiler and associated tools already installed, you
can install and use it.

The simplest approach is to clone the tool it from git, modify your
shell to use it, and then use it to install Python.  Here's a sample
way to set it up.  This won't necessarily match your exact
requirements, but you can try it, and please come back if you have any
further questions:

1. Clone the git repo into your home directory

git clone https://github.com/pyenv/pyenv.git ~/.pyenv

Pyenv is very simple, conceptually.  It's just a set of shell scripts
to automate the process of fetching, compiling, and installing
versions of Python, and then massaging your shell to make sure the
versions you have installed are used in preference to anything else.
So now you have the tool, you need to configure your shell to use it.
I'm going to assume you're using Bash.

2. Make sure the contents of the pyenv tool is available on your path

echo 'export PYENV_ROOT="$HOME/.pyenv"' >> ~/.bash_profile
echo 'export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.bash_profile

Note - this might need to be .bashrc, or something else, depending on
your os/distro/setup.  However, in principle you're just making the
pyenv tool (which itself is just a set of shell scripts) available at
all times.

3. Set your shell to initialise the pyenv tool every time you start a new shell

echo -e 'if command -v pyenv 1>/dev/null 2>&1; then\n  eval "$(pyenv
init -)"\nfi' >> ~/.bash_profile

Again: this might need to be .bashrc

4. Now open a new shell, and check you have pyenv available:

$ pyenv
pyenv 1.2.9-2-g6309aaf2
Usage: pyenv <command> [<args>]

Some useful pyenv commands are:
   commands    List all available pyenv commands
   local       Set or show the local application-specific Python version
   global      Set or show the global Python version
   shell       Set or show the shell-specific Python version
   install     Install a Python version using python-build
   uninstall   Uninstall a specific Python version
   rehash      Rehash pyenv shims (run this after installing executables)
   version     Show the current Python version and its origin
   versions    List all Python versions available to pyenv
   which       Display the full path to an executable
   whence      List all Python versions that contain the given executable

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

If you don't have pyenv working at this stage, come back and I'll help
you troubleshoot.  Assuming you do, continue:

5. Now you can install a version of Python, locally :

pyenv install --list

This shows you the various options of Pythons you can install.  You
want the latest 2.7:

pyenv install 2.7.15

This will fetch the source code of Python, and compile and install it
for you, and place it in your local shell environment, where you can
use it.

If this step doesn't work, it's probably because your system doesn't
have a compiler and associated tools.  I can help you troubleshoot
that, but ultimately you'll need support from your system
administrator at this point.

Assuming it's install Python, now you just need to tell your shell
that you want to use it:

pyenv local 2.7.15

This will make your shell find your 2.7.15 installation ahead of the
system python:

$ python --version
Python 2.7.15

Now you can run and use your Python.

Any further questions, sing out.

S.