running other older versions of python

[snippsat]

if i install all these python versions ... 2.4,2.5,2.6,2.7,3.3,3.4,3.5,3.6 how do i keep them from getting mixed up?

I have told you about pyenv before,but you to not always listen

mint@mint ~ $ pyenv install --list
Available versions:
  2.1.3
  2.2.3
  2.3.7
  2.4
  2.4.1
  2.4.2
  2.4.3
  2.4.4
  2.4.5
  2.4.6
  2.5
.... to 3.6.4 and 3.8 dev

Install 2.4 and set is as global system version.

mint@mint ~ $ pyenv install 2.4
Downloading Python-2.4.tgz...
-> https://www.python.org/ftp/python/2.4/Python-2.4.tgz
Installing Python-2.4...
Installed Python-2.4 to /home/mint/.pyenv/versions/2.4

Downloading pip-1.1.tar.gz...
-> https://pypi.python.org/packages/source/p/pip/pip-1.1.tar.gz
Installing pip-1.1...
Installed pip-1.1 to /home/mint/.pyenv/versions/2.4

mint@mint ~ $ pyenv global 2.4
mint@mint ~ $ which python
/home/mint/.pyenv/shims/python
mint@mint ~ $ python -V
Python 2.4

mint@mint ~ $ pip --version 
pip 1.1 from /home/mint/.pyenv/versions/2.4/lib/python2.4/site-packages/pip-1.1-py2.4.egg (python 2.4

Back to early days with pip 1.1
So now is 2.4 the main system version.
Test a feature that was new in 2.5 with open and get syntax error in 2.4.

mint@mint ~ $ python
Python 2.4 (#1, Feb 26 2018, 14:34:49) 
[GCC 5.4.0 20160609] on linux4
Type "help", "copyright", "credits" or "license" for more information.
>>> with open('foo') as f:
  File "<stdin>", line 1
    with open('foo') as f:
            ^
SyntaxError: invalid syntax
>>> 

i am curious if anyone has tried running various versions of Python different than what is normally available to you on the system you run Python on.

It's part of my normal workflow,example always when doing web-development i will have it virtual environment.
pipenv is what i use most it's greeat,in 3.6 so in also virtual environment build in trough venv
Also sometime VirtualBox, Docker, Anaconda, DigitalOcean, Cloud9.