venv conflict at shell prompt

[Skaperen]

in the documentation:

Activating the virtual environment will change your shell’s prompt to show what virtual environment you’re using, and modify the environment so that running python will get you that particular version and installation of Python.

i need to be concerned with this because i already have things the change my shell's prompt at every command and already have a complex environment management system that could conflict with what the virtual environment is doing. that document does not describe how this stuff is done, leaving it as a black box. but, what i really need is a transparent box so that i can be on the outside looking in.

i am wondering how it can get a higher version of the python interpreter. does it have its own repository online to download from? what architectures does it have?

[Larz60+]

You should be using pyenv with venv, everything is super smooth after that, you can then change the version of python running in your virtual environment at will. Look at Snippsat's tutorials, he has good ones on Pyenv, and venv

[Skaperen]

i have python 2.7.12 (not used for anything new) and 3.5.2. i am wondering what other versions i can run.

i have dabbled around with Linux Containers at the system level as opposed to black box tools like Docker (primarily for running services). this can be done with quite low overhead

one thing i wonder is how venv and pyenv deal with scripts that have coded the host interpreter path, on the hash-bang or elsewhere including my version switcher:

if bytes == str:
    import os,sys
    for p in os.environ.get('PATH','').split(':'):
        if p and os.path.exists(p+'/python3'):
            os.execvp(p+'/python3',['python3']+sys.argv)

the above code would normally be inserted into a file. i suppose it might work as a module but i suggest inserting it into the file you want to have run in python3. it's not that big.

[Larz60+]

These are the versions available with pyenv, you install what you want one time only using pyenv install versionname.
It is then immediately available to to be used at whim on every virtual environment that you have (will put in python tags since scrolling is available:
Install is simple, foe example:

pyenv install 3.6.0

The list:

$ 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
  2.5.1
  2.5.2
  2.5.3
  2.5.4
  2.5.5
  2.5.6
  2.6.6
  2.6.7
  2.6.8
  2.6.9
  2.7-dev
  2.7
  2.7.1
  2.7.2
  2.7.3
  2.7.4
  2.7.5
  2.7.6
  2.7.7
  2.7.8
  2.7.9
  2.7.10
  2.7.11
  2.7.12
  2.7.13
  2.7.14
  2.7.15
  3.0.1
  3.1
  3.1.1
  3.1.2
  3.1.3
  3.1.4
  3.1.5
  3.2
  3.2.1
  3.2.2
  3.2.3
  3.2.4
  3.2.5
  3.2.6
  3.3.0
  3.3.1
  3.3.2
  3.3.3
  3.3.4
  3.3.5
  3.3.6
  3.3.7
  3.4.0
  3.4-dev
  3.4.1
  3.4.2
  3.4.3
  3.4.4
  3.4.5
  3.4.6
  3.4.7
  3.4.8
  3.4.9
  3.5.0
  3.5-dev
  3.5.1
  3.5.2
  3.5.3
  3.5.4
  3.5.5
  3.5.6
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