On 02/03/11 08:06, Guido van Rossum wrote:
On Tue, Mar 1, 2011 at 1:26 PM, Eric Smith<eric@trueblade.com> wrote:
On 3/1/2011 4:19 PM, Kerrick Staley wrote:
Hello, There is a need for the default Python2 install to place a symlink at /usr/bin/python2 that points to /usr/bin/python, or for the documentation to recommend that packagers ensure that python2 is defined. Also, all documentation should be changed to recommend that "#!/usr/bin/env python2" be used as the shebang for Python 2 scripts. This is needed because some distributions (Arch Linux, in particular), point /usr/bin/python to /usr/bin/python3, while others (including Slackware, Debian, and the BSDs, probably more) do not even define the python2 command. This means that a script has no way of achieving cross-platform compatibility. The point at which many distributions begin to alias /usr/bin/python to /usr/bin/python3 is due soon, and for the next couple of years, it would be best to use a python2 or python3 shebang in all scripts, making no assumptions about plain python, which should only be invoked interactively. This email from about 3 years ago seems relevant: : http://mail.python.org/pipermail/python-3000/2008-March/012421.html Again, this issue needs to be addressed by the Python developers themselves so that different *nix distributions will handle it consistently, allowing Python scripts to continue to be cross-platform.
I believe we agreed at the language summit last year (or maybe even the year before) that "python" would always be python2.x, and "python3" would be python3.x.
And by "always" we indeed meant forever. To do otherwise would break scripts even many, many years from now.
Unfortunately distros are not following these guidelines. As long as we still have the pythonX.Y links I think it's better to have "python2", "python3" and "python" than total anarchy.
This was brought up when Arch Linux switched /usr/bin/python to point a python3 around six months ago, and at the time no-one could actually recall the decision to always point /usr/bin/python at python2 forever. In fact, the only decision that was clearly made (and acted on) was that "make install" for python3 would install /usr/bin/python3. e.g. http://www.mail-archive.com/python-dev@python.org/msg53204.html But if that decision was made, it was not documented anywhere that I can find, so effectively was a non-decision... Deciding that /usr/bin/python going to always point at python2 just makes me think that python3 is always going to be a second class citizen. Eventually python-2.7 will be long gone and it would seem wrong for people will still be using "python3" to run their scripts once python-3.xx is the primary python version. So a transition is going to need to be made here at some stage. Most distributions have been providing the /usr/bin/python2 symlink for a long time, with Debian being the notable exception. I think adding such a symlink is in the realm of what distribution packagers can choose to do on their own, but having it done automatically for python-2.7 would also be of benefit. Allan