[Python-Dev] Single-file Python executables (was: Computed Goto dispatch for Python 2)

[M.-A. Lemburg]

You might want to have a look at eGenix PyRun, which gives you
an almost complete Python runtime in 4-13MB (depending on what
startup performance needs you have):

http://www.egenix.com/products/python/PyRun/

On 28.05.2015 17:58, Barry Warsaw wrote:
> On May 28, 2015, at 11:39 AM, Donald Stufft wrote:
> 
>> You don’t need a "fully functioning Python" for a single file binary, you
>> only need enough to actually run your application. For example, if you're
>> making an application that can download files over HTTP, you don't need to
>> include parts of the stdlib like xmlrpc, pickle, shelve, marshall, sqlite,
>> csv, email, mailcap, mailbox, imaplib, nntplib, etc.
> 
> There are actually two related but different use cases to "single file
> executables".
> 
> The first is nicely solved by tools like pex, where you don't need to include
> a fully functional Python at the head of the zip file because the environment
> you're deploying it into will have enough Python to make the zip work.  This
> can certainly result in smaller zip files.  This is the approach I took with
> Snappy Ubuntu Core support for Python 3, based on the current situation that
> the atomic upgrade client is written in Python 3.  If that changes and Python
> 3 is removed from the image, then this approach won't work.
> 
> pex (and others) does a great job at this, so unless there are things better
> refactored into upstream Python, I don't think we need to do much here.
> 
> The second use case is as you describe: put a complete functional Python
> environment at the head of the zip file so you don't need anything in the
> target deployment environment.  "Complete" can easily mean the entire stdlib,
> and although that would usually be more bloated than you normally need, hey,
> it's just some extra unused bits so who cares? <wink>.  I think this would be
> an excellent starting point which can be optimized to trim unnecessary bits
> later, maybe by third party tools.

See above. This is what eGenix PyRun provides.

Our main motivation is to have a binary which works on all
Unix platforms, without having to rely on the way too many
system dependent Python distribution (with all their quirks
and whistles ;-)).

On Windows, we use py2exe at the moment, but a port of PyRun
to Windows would be possible as well. You'd still need the
separate Python DLL, though in order to stay compatible to
C extensions which link against this.

As for application packaging: we don't have a need to put
everything into a single ZIP file or even concatenate such
a ZIP file to PyRun (which is possible: just add sys.executable to
sys.path to import from the executable).

We have plans to create a tool to make such packaging possible,
though, since it's handy to have for building small executable
apps, e.g. to drive installations or larger applications.

>> Of course deciding which pieces you include in the zip file you're appending
>> to the end of Python is up to whatever tool builds this executable which
>> doesn't need to be part of Python itself. If Python itself gained the ability
>> to operate in that manner than third party tools could handle trying to do
>> the optimizations where it only includes the things it actually needs in the
>> stdlib and excludes things it doesn't. The key thing here is that since
>> you're doing a single file binary, you don't need to have a Python which is
>> suitable to execute random Python code, you only need one that is suitable to
>> execute this particular code so you can specialize what that includes.
> 
> I'd love to see Python itself gain such a tool, but if it had the critical
> pieces to execute in this way, that would enable a common approach to
> supporting this in third party tools, on a variety of platforms.
> 
> I do think single-file executables are an important piece to Python's
> long-term competitiveness.

-- 
Marc-Andre Lemburg
eGenix.com

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