[Python-ideas] npm-style venv-aware launcher

[David Townshend]

On Sun, May 31, 2015 at 9:35 AM, Andrew Barnert <abarnert at yahoo.com> wrote:

> On May 31, 2015, at 00:16, David Townshend <aquavitae69 at gmail.com> wrote:
>
> Pip and venv have done a lot to improve the accessibility and ease of
> installing python packages, but I believe there is still a lot of room for
> improvement.  I only realised how cumbersome I find working with python
> packages when I recently spent a lot of time on a javascript project using
> npm.  A bit of googling and I found several articles discussing pip, venv
> and npm, and all of them seemed to say the same thing, i.e. pip/venv could
> learn a lot from npm.
>
> My proposal revolves around two issues:
>
>    1. Setting up and working with virtual environments can be onerous.
>    Creating one is easy enough, but using them means remembering to run
>    `source activate` every time, which also means remembering which venv is
>    used for which project.  Not a major issue, but still and annoyance.
>
> If you're not using virtualenvwrapper.
>
> You do have to get used to using workon instead of cd to switch between
> environments--although if you want to, there's a hook you can alias cd to
> (virtualenvwrapperhelper). And I haven't tried either the native Windows
> cmd or PowerShell ports or the PowerShell port (it works great with MSYS
> bash, but I realize not everyone on Windows wants to pretend they're not on
> Windows). And managing multiple environments with different Python versions
> (at least different versions of 2.x or different versions of 3.x) could be
> nicer.
>
> But I think it does 90% of what you're looking for, and I think it might
> be easier to add the other 10% to virtualenvwrapper than to start from
> scratch. And it works with 2.6-3.3 as well as 3.4+ (with virtualenv instead
> of venv, of course), on most platforms. with multiple environments, with
> tab completion (at least in bash and zsh), etc.
>

Virtualenvwrapper does help a bit, but nowhere near 90%.  It doesn't touch
any of the issues with pip, it still requires configuration and manually
ensuring that the venv is activated.  But the biggest issue with extending
it is that it has a totally different workflow philosophy in that it
enforces a separation between the venv and the project, whereas my proposal
involves more integration of the two.  I have used virtualenvwrapper quite
a bit in the past, but in the end I've always found it easier to just work
with venv because of the lack of flexibiltiy in where and how I store the
venvs.

>
>    1. Managing lists of required packages is not nearly as easy as in npm
>    since these is no equivalent to `npm install --save ...`.  The best that
>    pip offers is `pip freeze`.  Howevere, using that is a) an extra step to
>    remember and b) includes all implied dependencies which is not ideal.
>
> My proposal is to use a similar model to npm, where each project has a
> `venvrc` file which lets python-related tools know which environment to
> use.  In order to showcase the sort of funcionality I'm proposing, I've
> created a basic example on github (https://github.com/aquavitae/pyle).
> This is currently py3.4 on linux only and very pre-alpha.  Once I've added
> a few more features that I have in mind (e.g. multiple venvs) I'll add it
> to pypi and if there is sufficient interest I'd be happy to write up a PEP
> for getting it into the stdlib.
>
> Does this seem like the sort of tool that would be useful in the stdlib?
>
> Regards
>
> David
>
>
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