On which unix distributions is Python installed as part of the default install?
Just looking at the systems available to me here:
Red Hat Enterprise Linux and its close relatives (Fedora, CentOS, Scientific Linux, Oracle Linux...) will always have Python installed since the installer and many core tools are written in Python.
Ubuntu has had Python installed by default since at least version 8.04.
Debian currently ships with Python installed by default.
Mac OS X has shipped with Python installed by default going back to at least 10.3.
OpenIndiana currently ships with Python installed by default. I assume that means Solaris also does, but I do not have a system here to test.
Python is not installed by default in any of the BSDs, unless you count OS X. You may well find that it is available on a BSD system because it was added after the system was installed. If not, it is available through the default package system in all cases:
FreeBSD includes Python in the Ports system:
/usr/ports/lang/python
OpenBSD includes Python in its package system:
sudo pkg_add python
NetBSD includes Python in its
pkgsrc
system, inlang/python*
Daniel Roseman got it right, i think all major distributions have python installed by default as its used for many (if not most) applications for the Gnome/KDE desktop enviroments (at least).
See this answer on a similar question on StackOverflow.
Also, this page of the Python documentation, says pratically the same thing:
Python comes preinstalled on most Linux distributions, and is available as a package on all others.
On Gentoo, Python is one of the very few things that need to be contained in an install, because its core package management system, portage, is written in Python+bash.