[Python-3000] [Python-ideas] Namespaces are one honking great idea -- let's do more of those!

[Stephen J. Turnbull]

Greg Ewing writes:

 > I just think the python2 and python3 worlds should be
 > kept separate by default, seeing as there are both forwards
 > and backwards incompatibilities.

I'm afraid that's exactly what will happen: the two worlds will tend
to be *kept* separate despite the common ground.

 > A specified app seems quite a likely reason to me.

My point is that they'll install that Python for use only by the app.
They won't want to change their default Python.

 > And if they've gotten used to "python" taking them to python3.x,
 > they'll get a surprise when it suddenly starts pointing to 2.x
 > after they installed an older Python for what to them was meant to
 > be a restricted purpose.

I wonder how many people out there will be "surprised" by sudden
changes in the version of Python installed.  On Mac OS X 10.4 +
MacPorts, MacPorts does not install an /opt/local/bin/python at all,
so that although /opt/local/bin takes precedence over /usr/bin, you
get the default Mac OS X install of Python 2.3 as "python".  Linux
distributions (at least Debian and Gentoo) "anoint" a particular
Python version as the one that infrastructure software uses and that
is the default unless the user explicitly sets a different version as
"python".  Installing multiple versions of Python does not reset the
"python" link.

So it seems to me that this particular issue can easily be handled if
Python source builds by default only install a "python" link if (a)
there is none or (b) the newly installed version is an upgrade of the
current "python".