[Python-Dev] readd u'' literal support in 3.3? (original) (raw)

Terry Reedy tjreedy at udel.edu
Wed Dec 14 05:29:27 CET 2011

On 12/13/2011 6:36 PM, exarkun at twistedmatrix.com wrote:

On 09:37 pm, tjreedy at udel.edu wrote:

On 12/13/2011 10:54 AM, Vinay Sajip wrote:

I started writing a tool today, tentatively called '2to23', which aims to do this. It's basically 2to3, but with a package of custom fixers in a package 'lib2to23.fixers' adapted from the corresponding fixers in lib2to3.

When, some year in the future, people want to drop Python 2 compatibility from their Python23 code, they will need a 23to3 tool. No, they will not.

Yes they will, if you read my conditional statement properly.

Anyway, quibbling over the meaning of 'need' is quite useless. It has two shades of meaning: lack of something required, and lack of something desired. You could have made the valid part of your point without starting off as you did.

But I already implied that removal is less urgent when I wrote "When, some year in the future...".

They only need a 2to3 or 2to6 tool because Python 2 and Python 3 are not compatible with each other, but they want one program to be valid in Python 2 and Python 3 simultaneously.

They need the extra stuff inserted. They do not want to insert by hand. So by your narrow meaning of 'need', one could say that having the insertion done by program is a want, not a need.

When they decide they no longer care about Python 2, they can just stop taking care to keep their program valid as Python 2 and only take care to keep it a valid Python 3 program. There's no specific change to make, just a different approach to take with future maintenance.

You might say that they will want to immediately discard all of their legacy Python 2 support code. I suspect many of them will not want this; but either way it's a want, not a need.

If and when someone wants the extra stuff removed to eliminated both the extra run-time and mental overhead of having it around, and they do not want to remove it by hand, they will want and therefore need in the more general sense to have it done automatically. In both cases, addition and removal, the process is tedious and error-prone if done by hand.

-- Terry Jan Reedy

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