So what's wrong with __future__? (Was Re: Why "from __future__" stinks ...)

[Aahz Maruch]

In article <mailman.985568441.15878.python-list at python.org>,
Timothy Grant  <tjg at exceptionalminds.com> wrote:
>
>OK, here's where I show my ignorance. Why did it have to be 100%
>backward compatible? Things in this industry get changed every day
>that are not 100% backward compatible. I tend to think that this was
>one of Microsoft's biggest problems with their OS. They insisted on
>backward compatability. I often wonder how much long-term pain (crappy
>OS stability) could have been avoided if MS had convinced their users
>to accept a bit of short term pain when Win95 was introduced.

Note that we're talking about two layers of compatibility here:

* The hack of announcing an incompatible language change

* The incompatible language change itself

If you say that the hack should itself be incompatible, there's no point
in doing the hack at all.  The hack was developed to postpone (not
eliminate) the need to deal with the incompatible language change.

The problem is that part of the point of Python is to be able to pick up
a random piece of source code and use it.  *BUT*, it can be hard to tell
what versions of Python the code can run under.

Overall, this is an ugly solution, but given the axioms that Tim was
working with, probably the best possible solution in a short period of
time.  Change the axioms and you get a different solution....
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