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I think it's the opposite. When other languages make incompatible changes, they have serious problems (e.g perl6).

Previous versions of python were back-compatible. Java versions stress back-compatibility. I don't know if HN can find any counter-examples, of a language that thrived through an incompatible, code-breaking upgrade.

Python has done everything possible to avoid this fate, by maintaining 2.7. And I'm not even convinced python has gotten away with yet (e.g. kalite, offline khan academy, needs 2.7). RHEL may end up reversing this. Give it another ten years!

Amd the Enterprize is the most back-compatible thing you've ever seen. This change is going to break lots of code, and they will reverse or lose customers.




I don't know if HN can find any counter-examples, of a language that thrived through an incompatible, code-breaking upgrade.

Of course. Swift 3 is one example. Ruby 1.9, as others have pointed out, is another.

PHP is yet another, and perhaps more relevant because it is close to contemperaneous. It had its "Python 3 moment" with the migration to PHP 5. Lots of BC breakages.[0] That transition took about 3-4 years for most.[1] Most users are now on the current major version, 7, and the remainder on 5 are mostly using its latest release (EOL is EOY). No one uses 4.

[0] https://secure.php.net/manual/en/migration5.php

[1] https://web.archive.org/web/20110720002753/http://www.gophp5...


Swift 3 is compiled. So you can provide the binaries and be ok.

Ruby 1.9 is a great example of why you should not be too nice: they told everybody "you have a fews months, deal with it". The community moved. Python said "poor things, we understand, take those tools and years to do the thing", and the community cried, and did nothing.

PHP literally failed. They canceled V6 and jumped to V7.

The funniest part ?

None of those languages are even close to Python popularity.

Swift is not even used for most Apple codebase. Python supported even Atari.

Ruby and PHP has almost no use case outside of the web. Python is used by OS, on the web, in GIS, by data analysts, for CGI, in AI, for sysadmin, to make GUI, video games...

And Python is much, MUCH older. 1990. 4/5 years older than Ruby/PHP. It has way more technical debt to pay. Swift ? 2014

Yeah the migration was badly handled from some aspects. But honestly, given the challenge and track record of the competition, it's not too shabby.


Comparing Python and Ruby upgrades is not fair.

Ruby 1.9 was working mostly the same as 1.8 while provising 2-3x speed improvment, and new exciting features.

Python 3 breaks even the basic Python 2 hello world, everything was notably slower, and not anything new and exiciting feature-wise apart ubified string support.


Yes, Python really botched it.


PHP 4 to 5, which was what my comment was about, took a middle path and had success much faster than Python did.

Given how much you like Python, I'm surprised at the gall to argue that Python had more technical debt to clean up than PHP did.


The remark about PHP was the move from version four to five. It was a big move.


Swift is Apple’s baby and has a captive audience. Since Apple cannot even update their example code, I don’t think it proves any points about keeping up with a moving target.


Maybe I'm wrong, but I have the impression that Ruby is now an expert's language, and much less accessible to beginners than it used to be. And, while it remains useful and used, it's not growing...

When trying to learn it, I encountered incompatible examples and tutorials, complex and changing ways to update it... and then my toy code stopped working. I eventually found the cause of the code-breaking change, fixed it... thought a bit, and decided against ruby. That's just me though.


> I don't know if HN can find any counter-examples, of a language that thrived through an incompatible, code-breaking upgrade.

Ruby qualifies, I'd say. From 1.8 -> 1.9 there were syntax changes, changes to how strings worked and so on. Code written for 1.8 would not in general work on 1.9 and the other way around. While it was possible (sometimes with some extra if statements) to write code that worked on both versions I would definitely call it an incompatible, code-breaking upgrade.


It's notable that 1.9 came with a significant performance boost, so there was a good practical reason to want to upgrade. People were motivated by the prospect of their code running twice as fast - sure, the language was improved a bit too, but it's Ruby, it's already pretty nice, so that was hardly going to light a fire under anyone.

When Python 3 turned up and it was on average slower, my first thought was "well, good luck getting people to adopt that".


The fact that it was possible to write code that worked with both wasn't just so critical, though. It allowed you to upgrade your code incrementally to support 1.9 while doing regression testing on 1.8, and then come up with a deprecation schedule for 1.8.


Python could be written that way (2/3-compatible) as well and plenty of programs and modules were.


Uhhhh... sort of? I mean, I could go through all of the needless "why the hell did they make this partner incompatible also" stuff like, like removing u'' support (thai was added later), or all of the ludicrous breakage in the underlying APIs (like filesystem calls that made assumptions about character encoding that make no sense for the underlying Unix model and literally caused files to just disappear from iteration)... a lot of this stuff was fixed in later versions of Python 3, but that was years later, making it nearly impossible to deal with the existing land mines of people who had installed Python 3.0-3 (or even 3.4).

But what makes me shocked that you think that that is the case is basic basic stuff... I mean, as one obvious example, they changed the exception syntax. So, "uhhhh.... sure?" it was possible to make a program that ran on both 2 and 3, but it required using "try" with no variable assignment and then digging into Python's exception reflection support to recover the variable. And you had to do this every single time. (And of course a lot of the time the underlying core library would now throw different exceptions, making the situation all the more ludicrous.)

I had code that straddles the 1.8/1.9 boundary of Ruby, and even though I wasn't an expert at Ruby it was trivial to have code that worked for both (and I mean 100% correct: Unicode and everything; remember that neither Ruby 1.9 nor Python 3 added Unicode support, they only made Unicode support easier to obtain. for Python 2 there was already comprehensive, if non-default, support, and for Ruby 1.8 you just needed to be careful about where you did conversions).


Half of the problem you mention are either:

- if you tried to support Python < 2.7.

- if you tried to support Python < 3.3

But nobody used 3.0, 1 or 2. And supporting 2.6 is like supporting ruby 1.7 and 1.8 and 1.9. Which nobody did.

And it's easy to rewrite libs when really the language started to be used in 2004.

Or maybe not, given that "gem install" still regularly crashes on anything other than the top 20 packages, so it's still not a solved issue.


Python 3.0 came out in 2008 and 3.3 came out in 2012. Are you really saying that nobody used Python3 for the first 4 years of its existence? I was certainly using 3.1 and 3.2 back then.


Pretty much yes. Some Linux distrib where still using 2.6, and not a lot of them had even 3.2 in their packages.

Only a few like you and me tried it.

I can't recall of any big project or lib ever supporting < 3.3.


Blender was using py3k for quite a while before 3.3. I was doing blender dev work back then and can recall the almost immediate upgrades as soon as the newest python release came out -- kind of painful really since I prefered to use the fedora installed version instead of building from scratch so would often stall my dev work until fedora caught up to blender.

They jumped on so early the python devs were saying "WTF are you people thinking?!?"


Given blender is mostly c bindings and a huge code base, it's kinda impressive, and a good example that it's not an impossible task to migrate even a very hard project, let alone the most common ones.


It wasn't a migration as much as a bottom-up rewrite of the entire bpy and big chunks of blender itself. Most of the bindings are generated by makesrna at compile (compile compile?) time which is fairly simple once you go deep diving into the sources.

It actually takes a fair bit of shenanigans to get hand-coded bindings into blender, my last(?) patch was bindings for the kdtree and I had to do some convincing to get that accepted. I'd guess that 99% of bpy is generated bindings.

If they stuck with python 2 when they started the initial overhaul they'd probably still be using it since artists are very vocal when their scripts break.


Django never had support for python < 3.3 and numpy and scipy only supported python 3.2 and up. The story is similar for most other packages. So if you where using python with any of its major libraries then python 3 was pretty much useless for you the first 3-4 years.


Django had support for 3.2 and 3.3, but not 3.0 and 3.1. Django didn't add support for 3.x until it was able to drop 2.5 (Feb 2013).

https://docs.djangoproject.com/en/2.0/faq/install/#what-pyth...


it was possible to make a program that ran on both 2 and 3, but it required using "try" with no variable assignment and then digging into Python's exception reflection support to recover the variable.

What? The PEP that added the new syntax also added it to Python 2.6: https://www.python.org/dev/peps/pep-3110/#compatibility


> When other languages make incompatible changes, they have serious problems (e.g perl6).

Counter-example: The ruby 1.8 -> 1.9 -> 2.0 upgrade path. 1.9 introduced the whole encoding system, which was a major update at the time. It did break a lot of libraries that handled strings. Still, the change went over fairly quickly, partly because major players in the ruby world (rails) adopted the change. The update also brought clear benefits and it was clearly marked that 1.8 was going to go out of support. There are still some stragglers (centos 6, I'm looking in your direction), but it's clearly accepted that ruby 2.x is the standard that you should be writing code for.


> I don't know if HN can find any counter-examples, of a language that thrived through an incompatible, code-breaking upgrade.

Swift breaks every major version at least but not as often and on a large scale anymore with point releases as with 1.x and 2.x. Has been like that from the beginning and everybody that writes it accepted it.


> Java versions stress back-compatibility.

You reminded me of the java version incompatibility nightmares that once littered the enterprise landscape. If they do that now, it's because their history includes perhaps the worst set of incompatibility jumps of any popular language.




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