[Python-Dev] A future division proposal

Perry Greenfield perry@stsci.edu
Wed, 25 Jul 2001 11:02:21 -0400

Clearly the issue of changing the semantics of division is a very
[ahem] divisive one in the Python community. It seems to me that
providing a foolproof way of providing backwards compatibility 
would go a long way to reducing the ire of those with a lot of
code to inspect and change.

I'm not particularly thrilled with the suggestions made so far.
Suggesting that people continue to use an older version of Python
if they have a problem with it is especially unsatisfying.
Eventually that older version will have to be updated in some
manner (resulting in a fork of Python) or they will have to
make the necessary changes to their code (albeit over a longer

Providing a new division operator (//) that handles integer division
doesn't really solve the issue of inspecting the code either.
There isn't any automatic way of telling when / or // should be used
in old code.

Command line switches or other mechanisms to indicate that 
division should have different behavior will confuse those
trying to understand source code ("is this '/' a new or
old division?").

Why not provide yet another division operator for backwards
compatibility purpose? This operator would have exactly the 
same semantics as the current division operator. If this were
available, it should be a relatively simple matter to provide
a tool to convert all uses of the / operator to the new form 
for old code. With this solution, the code never has to be
manually inspected to work with the new version, instead, it
just has to be mechanically translated. The fact that the
operator has different semantics will be evident in the 
translated code.

I don't know what the best name or symbol would be (olddiv, ///?)
and admittedly it is ugly to have 3 division operators. But
the alternatives seem far, far uglier. Isn't this a case
where practicality beats purity (for keywords or operators)?

Perry Greenfield