Experimental Python interpreter snap

[XiaoGuo Liu]

Hi James,

Nice. This is a nice example showing how to reduce a python snap package.
A few days ago, I also made a small example to make use of the python3
coming with the core at:

https://github.com/liu-xiao-guo/httpstat

In the above example, I in fact do not package the python. It works.

Thanks & best regards,
XiaoGuo

On Mon, Feb 20, 2017 at 10:16 AM, James Henstridge <
james.henstridge at canonical.com> wrote:

> To learn a bit more about I put together a snap for Python 3.6.0,
> which can be installed with:
>
>     snap install --edge python36-jamesh
>
> You can then run "python36-jamesh.python3", which will give you the a
> Python shell running with strict confinement, with the full standard
> library available.
>
> Now I know Snapcraft already has support for packaging Python
> applications, so what benefits does this package add?  There were a
> few extra points in how I built the package:
>
> 1. the interpreter binary and extension modules all have appropriate
> $ORIGIN relative rpath set.
>
> 2. a sitecustomize.py is provided that will add
> $SNAP/lib/python3.6/site-packages to sys.path. (more on why this is
> useful later)
>
> This makes the interpreter fully relocatable in the file system while
> still being able to find the bundled libraries.  In turn, this means
> the interpreter is functional when exported to another snap via the
> content interface.
>
> To demonstrate this, I put together a trivial "hello world" snapcraft
> project here:
>
> https://github.com/jhenstridge/python-snap-pkg/tree/master/examples/hello-
> world
>
> After building this package, it can be run after installing and
> connecting the interface:
>
>     $ snap install --dangerous hello-world_0.1_amd64.snap
>     hello-world 0.1 installed
>     $ snap connect hello-world:python3 python36-jamesh:python3
>     $ hello-world
>     Hello world!
>
> Since the hello-world snap doesn't actually include Python, it is
> quite light weight (4 kB, which I think is as small as a squashfs
> gets).  The space savings may not be that great with a single snap
> (the interpreter snap is almost 20MB), but the space savings increase
> as you install more snaps using the interface.  It also means that we
> could upgrade to Python 3.6.1 (when it comes out) without rebuilding
> this snap.
>
> And since the interpreter is being run under the hello-world snap's
> confinement policy, it can do potentially do things the main
> "python36-jamesh.python3" binary can't.  For example, if you add the
> "network" plug, you'll be able to access the network.
>
> And the sitecustomize script will also mean the interpreter can locate
> packages shipped in the plug snap.
>
> I'd be interested in any suggestions or feedback about the snap.
>
> Thanks,
>
> James.
>
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-- 
XiaoGuo, Liu
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