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

[Steven D'Aprano]

On Thu, May 28, 2015 at 01:20:06PM -0400, Donald Stufft wrote:

> I think it’s an issue for all platforms, even when there is a system Python
> that can be used.
> 
> Here’s why:
> 
> * Even on Linux systems Python isn’t always a guaranteed thing to be installed,
>   for instance Debian works just fine without any Python installed.

Donald, are you a Linux user? If so, which distro? Because in the Linux 
world that I'm familiar with, this (and the points you make below) are 
absolutely not an issue. You let the package manager worry about 
dependencies:

yum install myapp  # Red Hat based distros
apt-get install myapp  # Debian based distros

will ensure that the right version of Python is installed.

In the circles I move in, installing anything which does not go through 
the package manager is considered to be quite dubious. In order of 
preference (best to worst):

- install from official distro repositories;
- install from a third-party repo;
- install from source;
- find an alternative application;
- do without;
- install from some binary format (also known as "would you like
  a root kit with that?").


[...]
> * Even if you have Python installed already, is it the right one? What if it’s
>   an ancient RHEL box that has 2.6 or (heaven forbid) 2.4? What if it’s a not
>   ancient box that has Python 2.7 but you want to deploy your app in Python 3?

Most recent distros have both a python2 and python3 package, and when 
building your rpm or deb file, you specify which is your dependency in 
the normal fashion.


> * What if you have Python installed already, but it’s been patched by the place
>   you got it from and now the behavior is different than what you expected?

Normally you would write for the version of Python provided by the 
distros you wish to support. In practice that might mean writing hybrid 
code targetting (say) 2.6 and 2.7, which covers most recent Red Hat and 
Debian based systems, and anything else, you provide the source code and 
let the user work it out.

I suppose that in principle you could include whatever version of Python 
you like *in your application*, but that would be considered an unusual 
thing to do. I believe that LibreOffice and OpenOffice do that, so they 
can support Python as a scripting language, but they're generally 
considered (1) a special case because they're cross-platform, and (2) 
not "proper" Unix or Linux apps anyway.

The point is, in the Linux circles I move in, this idea of single file 
installation would be about as popular as a police raid at a rave club. 
Maybe you move in different circles (perhaps more enterprisey?), but I 
can already imagine the sort of derogatory comments the sys admins I 
work with would make about this idea. 



-- 
Steve