Re: multiple pythons and the default
Bruce Sass wrote:
>> /usr/bin/python provided by the "python" package. Right now it's 2.3.5.
>
> So it is arbitrary, as in there is no technical reason which makes 2.3.5
> most suitable.
That impression is incorrect. There was a technical reason when the
default was defined: it was the most recent version that tat time.
The next default will have the same property: it will be the most recent
release. So the decision what Python version is the default is *not*
arbitrary.
> Therefore it should be possible to choose any Python as the
> default so long as the dependencies of any package depending on the official
> default Python can be satisfied, and any problem encountered in doing so
> would be problems with the implementation of a "default".
That conclusion is false, or at least misleading. A package depending
on the default version might not just depend on other packages that the
default Python would have to provide - it also might depend on the
specific behavior of the default Python version.
IOW, when the default Python version changes, some applications may
break, because they have not been ported to that other version. To
minimize the breakage, it is desirable that the default Python version
changes rarely (so that Python applications don't need to get ported
to a different version that often), and that the default only ever
changes to newer versions (so that applications never need to get
backported, only forward).
> Debian's support for multiple interpreters should be more than a
> convenient apt-get install some other Python interpreter, it should be
> the infrastructure necessary to manage multiple Pythons. Consider that if
> the system is designed so that an admin can easily change the default
> Python, then Debian can also.
What system is designed so that an admin can easily change the default
Python?
An admin might break his installation by changing the default; his
users will blame him for doing that. Debian shouldn't break the users'
systems so lightly.
> If a package depends on Python-2.4 then it should actually depend on
> python2.4 and not some other package which just happens to pull in the
> necessary interpreter...
Why? This will give you many unnecessary hard-coded package
dependencies. Packages that are reasonably expected to work with this
current version and any future version should depend on the default
Python.
Regards,
Martin
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