search

mislav / anyenv

rbenv-inspired version manager that can be configured to manage versions of ANYTHING
MIT License
274 stars 12 forks source link

Support for multiple activated versions #3

Open blueyed opened 9 years ago

blueyed commented 9 years ago

pyenv support multiple versions.

It will try the versions in order.

% python --version
Python 3.4.3

% pyenv shell 2.7.9:3.4.3
% python --version
Python 2.7.9

% pyenv version
3.4.3 (set by /home/user/.pyenv/version)
2.7.9 (set by /home/user/.pyenv/version)

% cat .pyenv/version
3.4.3
2.7.9

% pyenv version-name 
3.4.3:2.7.9

% pyenv versions 
  system
  …
* 2.7.9 (set by /home/daniel/.pyenv/version)
  …
* 3.4.3 (set by /home/daniel/.pyenv/version)
  …

When trying to run a shim from a version that's not activated, you'll see a list of versions where it is available (that might be the case for rbenv/anyenv already):

% easy_install-2.6 
pyenv: easy_install-2.6: command not found

The `easy_install-2.6' command exists in these Python versions:
  2.6.9
mislav commented 9 years ago

Interesting, thanks for letting me know. Why is this feature baked into pyenv? Doesn't it make it difficult to be certain about which exact version will be used for running a python program? To me it seems that the whole point of a rbenv-like manager is to lock a version down with absolute precision. Thanks

blueyed commented 9 years ago

In Python you often have to run Python 2 and 3 in parallel.

Apart from that, there are tools like tox, which run tests in different Python versions, and that needs to have them available, too.

If you use python you'll get the first/locked version, but the other versions might provide the other interpreter (python-2.7), or some tool, which was installed using pip2 (instead of pip or pip3).

Then there are also virtualenvs, which are handled like versions through https://github.com/yyuu/pyenv-virtualenv.

So you can use venv-name:3.4.3 as your pyenv-version, which would use the virtualenv, but fall back to your 3.4.3 version (for running shims).

mislav commented 9 years ago

If you use python you'll get the first/locked version, but the other versions might provide the other interpreter (python-2.7), or some tool, which was installed using pip2 (instead of pip or pip3).

Wow, that's… confusing. But it sounds like this fallback could theoretically be done via a python-specific plugin for anyenv. The whole idea of the fallback if an executable isn't found in the current version reminds me of https://github.com/sstephenson/rbenv/issues/187