Python 2.6 to Smooth the Way for 3.0, Coming Next Month

darthcamaro writes "Some programming languages just move on to major version numbers, leaving older legacy versions (and users) behind, but that's not the plan for Python. Python 2.6 has the key goal of trying to ensure compatibility between Python 2.x and Python 3.0, which is due out in a month's time. From the article: 'Once you have your code running on 2.6, you can start getting ready for 3.0 in a number of ways,' Guido Van Rossum said. 'In particular, you can turn on "Py3k warnings," which will warn you about obsolete usage patterns for which alternatives already exist in 2.6. You can then change your code to use the modern alternative, and this will make you more ready for 3.0.'"

Comments

Not sure about this one

[the eric conspiracy]

Why not just wait for 3.0 to make the changes? That way you'll only have to test everything once.

And if it's like some other languages you might have a long time to wait before 3.0.

Re:Not sure about this one

[jeremiahstanley]

Because the development cycle is longer than that for derivative projects. Imagine if you could have a cycled and tested app that was ready from day 0...

Re:Not sure about this one

[arevos]

And if it's like some other languages you might have a long time to wait before 3.0.

Given that the first release candidate of Python 3.0 is already out, I doubt we'll be in for a very long wait.

Re:Not sure about this one

[AM088]

I think the point is that with 2.6, your old code will work but will tell you what to change. If you move to 3.0, unless you have those changes already, it just won't work.

Re:Not sure about this one

[fyngyrz]

If you move to 3.0, unless you have those changes already, it just won't work.

...which is why some heavy python users, myself included, aren't going to use 2.6 or 3.0. I have huge amounts of python in operation, and the very last thing I'm going to do is break any of it with an incompatible language that happens to slightly resemble python (no matter who wrote it, and no matter what they call it, it isn't python if it can't run mundane python code.)

Every once in a while we see one of these "brainstorms"; for example, Microsoft pulled VB from the office suite... only to put it back. Because the idea was stupid; there was a ton of production code / applications they flat out broke. Python's doing exactly the same thing, and it's not going to work out for the same reason(s.)

If you're going to modify a language, you *must* do it in a compatible manner, otherwise what you're doing is making a new language that will require an entirely new community. Names notwithstanding, and resemblance beyond incompatibilities notwithstanding.

Re:Not sure about this one

[tazzzzz]

...which is why some heavy python users, myself included, aren't going to use 2.6 or 3.0. I have huge amounts of python in operation, and the very last thing I'm going to do is break any of it with an incompatible language that happens to slightly resemble python (no matter who wrote it, and no matter what they call it, it isn't python if it can't run mundane python code.)

"slightly resemble python"? Python 3.0 code looks just like the Python that's been around for years. Maybe there's some handy new syntax (with), but it's still Python.

This is not about fundamentally changing Python. This is about cleaning up warts, some of which have been around since Python 1.x.

If you're going to modify a language, you *must* do it in a compatible manner, otherwise what you're doing is making a new language that will require an entirely new community. Names notwithstanding, and resemblance beyond incompatibilities notwithstanding.

From what I've seen, the Python devs have put together about the best possible migration path while still actually making the changes that need to be made.

Here's the picture, in case it's not clear: Python 2.6 is just as backwards compatible as the other 2.x releases. Which is to say that porting from 2.5 to 2.6 is pretty trivial. I'd expect any actively used and maintained library to be 2.6 compatible within weeks (and a great many probably didn't break at all).

2.6 lets you use many of 3.0's features that don't break compatibility (and there are many). It also has a warnings mode to help you spot 3.0 incompatible code. And it lets you selectively turn on 3.0 features within a module.

Want to start using the new print function?

from __future__ import print_fiunction

Voila! The print keyword goes away and you have the new print function. Certainly bits of new Python 3.0 syntax work now as well:

try:
        1/0
except ZeroDivisionError as e:
        pass

The "as e" bit is new.

Finally, there's actually a "2to3" tool that makes many of the changes in an automated fashion.

The single biggest change from a compatibility standpoint is that "foo" is a unicode object in 3.0 and a string (set of bytes) in 2.x. You can even prepare for that switch:

from __future__ import unicode_literals

foo = "foo" # this will be unicode
bar = b"bar" # this is a set of bytes
unibar = bar.decode("utf-8") # get a unicode from the bytes

They have put *a lot* of thought into how to make this transition. People will gradually shift to 2.6, just as they did with 2.5. And, over time, they will change to using the new features. They'll probably upgrade to 2.7 (yes, there will be one), and use the new features even more. And eventually their code will just be 3.0 code and the switch will be a no brainer.

Re:Not sure about this one

[MightyYar]

If not, why wouldn't I just wait for 3.0 and then just fix everything ONCE?

Well, first of all, 2.6 and 3.0 come out at the same time and share many of the same new features... so there's no "just wait for 3.0" possible, it's either/or right now.

The advantage is that if you have a big pile of 2.5 code right now, you can slowly turn on the "use 3.0 style" switches in 2.6 and migrate your code one little switch at a time over a long period of time.

That way, a few years from now when they decide to stop supporting new features in the 2.x path and you really "must have" some new feature in the 3.x path, it will be significantly easier for you to switch if you've turned on the "use 3.0" switches previously.

Re:More ready?

[Onaga]

But which one is correcter?

tough transitions

[AceJohnny]

These kind of compatibility switches are make-or-break. I'm glad there's Python 2.6 to try to ease the problem, but Py3k means that everybody who publishes python software will all of a sudden have to maintain 2 branches, for Python 2.X line and Python 3.X line.

This isn't the same as one software package having "legacy" and "bleeding edge" branches, because that's their own choice. In this case the underlying language is forcing them to choose.

Honestly, I'm not confident in the economics of such transitions, and believe Py3k will die out.

Re:tough transitions

[imbaczek]

it'll take several years, but a critical mass will switch eventually IMHO.

Re:tough transitions

[Anonymous Coward]

Honestly, I'm not confident in the economics of such transitions, and believe Py3k will die out.

Why would Python 3.0 'die out'? Even if you don't believe existing projects will make the switch there's no reason why new projects won't want to have the considerable benefits of using Python 3.0.

Re:tough transitions

[DragonWriter]

These kind of compatibility switches are make-or-break. I'm glad there's Python 2.6 to try to ease the problem, but Py3k means that everybody who publishes python software will all of a sudden have to maintain 2 branches, for Python 2.X line and Python 3.X line.

No, they don't "have to" maintain two branches. They can choose to, or they can maintain one (which depends on their particular circumstance); if necessary (if it is an app and not a library) they can just distribute the right interpreter with the app.

This isn't the same as one software package having "legacy" and "bleeding edge" branches, because that's their own choice.

Yeah, actually, it is exactly the same as that, at least as long as bug-fixes and maintenance continues on Python 2.x: the "one software package" being the Python interpreter.

And, yeah, if those maintaining python-based projects choose to maintain Python-2.x and Python-3.x based versions, that will also be an instance of exactly what you say it wouldn't be, as it will still be their own choice.

Re:tough transitions

[GooberToo]

Why would Python 3.0 'die out'?

Its widely believed a large asteroid fell from the sky and wiped the mighty python 3.0 out. ;)
 

Re:tough transitions

[GooberToo]

For whatever reason, people fail to understand python natively supports parallel installs. Furthermore, since python's preferred script magic is "#!/bin/env python", rather than, "#!/bin/python", the executing script will use the python that it finds in your path. Additionally, you can also tie python to a specific version as "python2.5". Want a different python? Change your path. A script requires a specific version of python? Change the script to require it. It's one line and trivial. It's at the top of the file, so there's no hunting even.

New python releases only pose problems for the uninitiated, the ignorant, or the dumb.

Re:tough transitions

[Anonymous Coward]

Honestly, I'm not confident in the economics of such transitions, and believe Py3k will die out.

No wireless. Less space than a nomad. Lame.

Re:tough transitions

[xant]

Uh, it's almost exactly the opposite of what you're saying. You don't have to have a Python 3.x line; you can just deploy your code on Python 2.6, keep your working application working, and do all your new development and testing with Python 3.x warnings turned on. Then your next release is Python 3.0 compatible; or if you somehow fail to do finish the Python 3.x upgrades in time for your next release, you don't have to release on Python 3.x, you can just keep using Python 2.6 even though your code is partially upgraded.

Partially upgraded codelines are always the problem with major version upgrades, and the Python 2.6/3.0 future compatibility is designed precisely so that this problem is not a problem.

Python has bent over backwards to make the upgrade as easy as possible for people with serious Python applications in production.

Re:tough transitions

[jgrahn]

For whatever reason, people fail to understand python natively supports parallel installs. Furthermore, since python's preferred script magic is "#!/bin/env python", rather than, "#!/bin/python", the executing script will use the python that it finds in your path. Additionally, you can also tie python to a specific version as "python2.5". Want a different python? Change your path. A script requires a specific version of python? Change the script to require it. It's one line and trivial. It's at the top of the file, so there's no hunting even.

Changing my path is not practical. It's too broad. I'd have to write a shell script wrapper for the application which did 'env PATH=new_python:$PATH the_real_application "$*"' or something. And it's not just me; I'd have to communicate this to all other users of the system somehow. And changing one line of a script is not trivial, if I'm not root.

All this may seem like minor things, but it adds up. And no other good language puts me in situations like that.

New python releases only pose problems for the uninitiated, the ignorant, or the dumb.

Or those of us who have been around for a while, and seen innocent backwards-incompatible changes become maintenance nightmares ... Ok, maybe not a nightmare in this case, but an inconvenience and annoyance which will keep being inconvenient and annoying for years, until the last Python 2.x dependency goes away.

The best way to judge this would probably be to look at what Linux distributions like Debian want to do about Python 3.0. They ship one Python as the default (2.4 currently, for Debian) but provide others too. I bet even a change from 2.4 to 2.5 is a major migration for them.

What's new

[ChienAndalu]

Here are the changes.
I really have to check out the multiprocessing package. Too bad that I have to wait for the print function and the new division handling.

Re:What's new

[yuriyg]

Too bad that I have to wait for the print function and the new division handling.

Huh?
from __future__ import print_function
from __future__ import division

Re:More ready?

[Anonymous Coward]

Technically the correct term would be readier, but that sounds a little awkward to some people. Generally the rule is: One Syllable=[adjective]er More than one Syllable=more [adjective] Unfortunately very few people tend to adhere to this. They usually randomly pick one method or the other, or worse, they use both. (more readier).

Ready has two syllables.

Cut the crap.

[Anonymous Coward]

These changes are NOT earth-shattering. 2.6 is mostly just going to add a few new features, most important being the with statement. Most code written using Python idioms will be fine under 2.6 and 3.0. Now, if you tried to write Java-esque or C-esque code under Python, you might run into issues. Even then, I doubt it. They've been deprecating features for awhile, and 3.0 is probably the point at which they'll be yanked...you've only had a year or two of DeprecationWarnings.

I'm not sure why people whine about a language evolving. Retain backwards compatibility to a fault and you end up with C++, which is crippled by C-isms. You either know your code well enough that you could make the small incremental changes along the way, or you simply don't upgrade.

Python most needs sane standard libraries. It is far too much of a "let's throw this in there" with three different naming conventions and no package organization. It is a shame, because the language itself is pretty powerful in the right hands.

Re:Cut the crap.

[jimdread]

I'm not sure why people whine about a language evolving.

It's because all their old code breaks. And that hurts.

Re:Cut the crap.

[slimjim8094]

So don't use Python 3.0. If it's critical, you're not upgrading from a known working base anyways, right? And if it's not, this will hold your hand.

Really?

[Peaker]

What Python features broke for you between minor releases?

I find it pretty hard to believe any Python user would actually switch to Perl, and stick to it.

You sir, are probably making this story up :-)

String f**k up

[spitzak]

Reading the release, they have decided to really push 16-bit strings (they call this "Unicode" but it really is what is called UTF-16). I think this is a serious mistake.

The proper solution is to use 8-bit strings, but any functions that care (such as I/O) should treat them as being UTF-8. Most functions do not care and thus the treatment of "Unicode" and "bytes" are the same.

The problem with UTF-16 is you cannot losslessly convert a string that *might* be UTF-8 to UTF-16 and then back again. This is because any illegal UTF-8 byte sequences will be lost or altered. This is a MAJOR problem for code that wants to process data that is likely to be text but must not be altered under any circumstances, in effect such programs are forced to be ASCII-only, even though UTF-8 is purposly designed so that such programs could display all the Unicode characters. Note that bad UTF-16 (ie with mismatched surrogate pairs) can be losslessly converted to UTF-8 and back.

This has been a real pain so far in our use of Python, and I am quite alarmed to see that they are changing the meaning of plain quotes in 3.0 to "Unicode". This is really a serious step backwards, as we will be forced to tell anybody using our system to put 'b' before all their string constants and I suspect there will be a lot less automatic conversion of these strings to unicode when we want to display them. Note that Qt is also causing a lot of trouble here too.

Re:String f**k up

[Animats]

The problem is that there are three kinds of string-like objects in Python: UTF-16 strings, ASCII strings, and uninterpreted arrays of 8-bit bytes. Python 2.5 sort of supports all 3, with "array of bytes" the least well supported. Since this is a language without declarations, the semantics of this gets messy.

The most common problem was that functions like ".read()" yielded strings, not arrays of bytes. This follows C standard library semantics, but is a bad fit to Python. In 3.0, ".read()" yields an array of bytes, not a string. If the data read is to be converted to a string, "decode" is required. That's the right answer.

This is consistent with modern thinking about data representation. Consider SQL, which makes a similar distinction between "TEXT" and "BLOB".

Re:String f**k up

[John Millikin]

Spoken like somebody that's never had to deal with encoding issues. Using UTF-8 internally is fine, but exposing it to the programmer is insane and error-prone. And if the programmer then proceeds to manipulate that raw byte buffer as a string, he's an idiot.

The proper solution is to use 8-bit strings, but any functions that care (such as I/O) should treat them as being UTF-8. Most functions do not care and thus the treatment of "Unicode" and "bytes" are the same.

You might not be aware of this, but computers are used for more than just transmitting text. I don't want my binary streams being rewritten to gibberish because some I/O routine was written to be too clever. Furthermore, not every system uses UTF-8. Some may even need to send data over a *gasp* network! Good luck getting every other computer in the world to start using UTF-8 immediately.

The problem with UTF-16 is you cannot losslessly convert a string that *might* be UTF-8 to UTF-16 and then back again. This is because any illegal UTF-8 byte sequences will be lost or altered.

If you try to convert bytes that aren't in UTF-8 using a UTF-8 codec, an error will be raised. This behavior is proper -- if you don't know what format your input is in, there's no way to perform text-based operations on it.

This has been a real pain so far in our use of Python, and I am quite alarmed to see that they are changing the meaning of plain quotes in 3.0 to "Unicode".

Every developer I know uses Unicode strings already. The new behavior is just one less character to type in front of literals.

This is really a serious step backwards, as we will be forced to tell anybody using our system to put 'b' before all their string constants

Otherwise said as: "We're too stupid to fix the glaring encoding errors in our product, so we'll just use bytes everywhere and pretend it's all working". Also, Unicode strings in Python are implemented with either UTF-16 or UCS-4 depending on platform.

Re:String f**k up

[belmolis]

Python does not use UTF-16 strings; it uses UCS-2 strings. The difference is that in UCS-2, every character is represented by exactly two bytes, while in UTF-16, some characters, those outside Plane 0, are represented by two "surrogate" pairs, totaling four bytes. UCS-2 does not provide any representation for characters outside the BMP. In other words, UCS-2 is a straightforward fixed length encoding, while UTF-16 is a more complex variable-length encoding.

Python can in fact use either of two internal representations for text: UCS-2 or UTF-32 = UCS-4. If you give the option --enable-unicode=ucs4 to configure when building Python, you will get a Python that supports all of Unicode rather than just the BMP.

Re:String f**k up

[spitzak]

No, think a little harder.

Imagine a file system that names the files with strings of bytes.

It is absolutely vital that if I ask for a list of files and then try to open them, that this all work, no matter what byte sequence has managed to get in there as a filename.

It is also *nice* but nowhere near as vital that I be able to show these names to users and they read them as Unicode strings.

Re:String f**k up

[spitzak]

You might not be aware of this, but computers are used for more than just transmitting text. I don't want my binary streams being rewritten to gibberish because some I/O routine was written to be too clever

Thank you for explaining exactly why I want UTF-8 to be used, while thinking you were arguing against it.

Data is NOT just text. Therefore we should not be mangling it because we think it is text. We have enough trouble with MSDOS inserting \r characters. This crap is a million times worse.

Re:String f**k up

[spitzak]

People expect a string to be a sequence of characters. Please notice the first word in that sentence.

"People" are not computers. "people" LOOK at the display. People are not trying to copy the data literally from one place to another or do comparisons of strings or read files that might (horrors) not contain correct UTF-8 data. There is no reason to mangle the data until the very last moment before it is put on the display.

I can quite confirm that if you have more than one way to represent the same sequence (such as different ways of producing the same UTF-8 error) you will produce a MAJOR screw up, quite likely an exploitable security hole. It also is not nice if "copy" mangles data just because it had a sequence that could not be coinverted correctly to glyphs.

Re:String f**k up

[spitzak]

Spoken like somebody that's never had to deal with encoding issues. Using UTF-8 internally is fine, but exposing it to the programmer is insane and error-prone. And if the programmer then proceeds to manipulate that raw byte buffer as a string, he's an idiot.

The compiler will turn "unicode" into the utf-8 encoding. The programmer does not see \xnn sequences of the utf-8 bytes. Try some modern compilers with utf-8 support some day before you say anything stupid again.

Any programmer that modifies UTF-16 as a raw array of words is an idiot. Besides surrogate pairs, there are combining characters and bidirectional indicators and lots of other trouble. In fact I prefer UTF-8 exactly because it discourages such misuse of strings, which are really made of words, sentences, etc.

If you try to convert bytes that aren't in UTF-8 using a UTF-8 codec, an error will be raised. This behavior is proper -- if you don't know what format your input is in, there's no way to perform text-based operations on it.

You have just introduced a massive DOS hole into your programs. Or do you really think you should run a "is this correct UTF-8" call before any attempt to convert? Sorry, it is not going to raise an error, it will instead convert to error UTF-16 characters.

Every developer I know uses Unicode strings already. The new behavior is just one less character to type in front of literals.

You know that Python will convert your bytes from UTF-8 to "Unicode" automatically when needed? No you didn't? Might want to study up on that...

Otherwise said as: "We're too stupid to fix the glaring encoding errors in our product

The encoding errors are not in our product. They are in the files we are attempting to read (metadata attached to images, mostly). Dumbass

Re:String f**k up

[spitzak]

I think the lesson is that there is ONLY byte sequences.

The fact that some code can interpret that byte sequence and draw something on the screen that the user thinks of as "text" is completely irrelevant and should not be a fundemental datatype of a programming language. This should be part of the code that draws the text. Imagine if every other type of data, such as image pixels, or sound samples, had a different IO routine and you could never read a file with the wrong routine because the conversion was lossy.

The real problem is that everybody's mind has been polluted by decades of ASCII where there was no difference between characters and bytes. All I can suggest is to try to think of text as words or sentences. Nobody would suggest that it would be good to make all words use the same amount of storage, or that it is important that you be unable to split a string except at word boundaries. But there has been so much use of ASCII that people think this is important for "characters".

I also believe there is a serious politically-correctness problem. Otherwise logical programmers are consumed with guilt because Americans get the "better" short encodings, and therefore feel they have to punish themselves by making the conversion to i18n as painful as possible so that Americans have just as much trouble as anybody else. The fact that they have actually made I18N far harder for everybody and thus actually discouraged it is the ironic result of this guilt.

Re:String f**k up

[Animats]

From What's new in Python 3.0: The str and bytes types cannot be mixed; you must always explicitly convert between them, using the str.encode() (str -> bytes) or bytes.decode() (bytes -> str) methods.

That's the right way to do it, but I agree that as a retrofit to existing code, it's a headache.

Worse, it's a problem that's detected at run time, not compile time, at least with the CPython implementation.

Re:String f**k up

[belmolis]

In fact I am better informed than you are. When not compiled to use UCS-4, Python uses what is properly called UCS-2, with half-baked extensions for treating it as UTF-16. Certain functions know about surrogate pairs, such as those that convert between UTF-8 and the internal representation. However, such basic functions as len do not know about surrogate pairs. Try giving a character outside the BMP as the argument to len. It will return 2, not 1.

Re:String f**k up

[tazzzzz]

Reading the release, they have decided to really push 16-bit strings (they call this "Unicode" but it really is what is called UTF-16). I think this is a serious mistake.

The proper solution is to use 8-bit strings, but any functions that care (such as I/O) should treat them as being UTF-8. Most functions do not care and thus the treatment of "Unicode" and "bytes" are the same.

I'm going to try once more, slightly differently. Two other people apparently have tried and failed.

Python 3.0's handling of strings is basically the same as Java's, because it has proven to work quite well there.

For webapps, and the rules may be a little different on the desktop, "best practices" in Python for some time have been that you use unicode objects everywhere internally when you are representing text. When you hit a boundary (a file on disk, the net), you encode that unicode string into whatever encoding makes sense (often UTF-8). So far, so good, I hope?

Python's internal representation of unicode objects is only relevant in that you need it to support whatever code points you care about. I don't think there are any code points that you can represent in UTF-8 that Python will screw up after decoding/encoding. I'm sure there are many people who would be interested to see such a test case.

If you have a bunch of bytes that *might* be UTF-8, you're screwed. "process data that is likely to be text but must not be altered"? What do you mean by text? 7-bit ASCII? UTF-8? And where is the text coming from? Unless you tell Python the encoding of the file, you're going to get bytes out, not unicode objects.

The whole point is that Python unicode objects know how to represent code points. If you have get a set of bytes from somewhere you *have* to know what encoding it is in order to be able to treat it as a bunch of text characters. Python unicode objects will not be "bad UTF-16". How they're stored is not generally important. What's important is that Python internally keeps track of the code points and will either successfully convert to whatever encoded sequence of bytes you want or it will raise an exception because the encoding you've chosen doesn't have one of the characters in your string.

Python 3.0 makes this all clearer. When you talk about a "string", you're talking about a bunch of unicode characters. Anything else is a collection of bytes.

By the way, you can specify what encoding a Python source file is in so that your string literals are all properly decoded.

For further reading...
http://www.joelonsoftware.com/articles/Unicode.html

Re:String f**k up

[tazzzzz]

Actually, this has been explicit in Python for some time. In Python 2.x, "string" objects are byte sequences and "unicode" objects are character sequences.

What changes in Python 3.0 is that "unicode" objects have been renamed "string" and "string" objects have been renamed "bytes". So, not only is it explicit, but the naming makes more sense.

The other related change is that string literals in your code are interpreted as Python 3.0 "string" objects ("unicode" in Python 2.x terminology), whereas previously you had to stick a 'u' in front of the string to get that behavior. And you can indeed specify the encoding of your source files, which is nothing new.

All of this to say, you're right on the money and Python is already in the spot you describe as "better off".

Re:String f**k up

[earthbound kid]

The proper solution is to do what they did: hide from the programmer what internal format is used for strings. The only time programmers should know about the encoding is when they themselves explicitly select an encoding so that they can turn a bunch of bytes into a string or when they're sending the string out into the world as a bunch of bytes. Encode and decode explicitly at the edges. Internally, hide the implementation details. It's just basic OO.

Not really

[widman]

You can keep your code compatible with both at the same time. Deprecated features are trivial to rewrite in most cases. There are even tools for this.

Doesn't matter

[morgan_greywolf]

Most distros already include the current and previous versions of Python. So Ubuntu, for instance, will include 2.6 and 3.0, and possibly 2.5 as well.

Furthermore, you can check to see what version of Python you're running under and make your code so that it accomodates both. This is all accessible via sys.version or sys.version_info

>>> sys.version
'2.5.1 (r251:54863, Jul 31 2008, 22:53:39) \n[GCC 4.1.2 (Ubuntu 4.1.2-0ubuntu4)]
>>> sys.version_info
(2, 5, 1, 'final', 0)

With that knowledge, you just put all your version specific stuff in modules.

So you can do a:

import sys
major,minor,micro,release,release_num = sys.version
if (major > 3):
        import module_for_python_3.0
else:
        import module_for_python_2.x

Module support for 3.0 is a long way off

[Animats]

Many essential third party libraries need to be converted for Python 3.0. I need M2Crypto (SSL support) and MySQLdb (MySQL support), neither of which is ready for Python 3.0, and neither of which has been updated in the last year or so.

My guess is that it will be three years before stock mainstream Linux distros come with Python 3.0 and a set of libraries that work with it.

Re:Module support for 3.0 is a long way off

[Ixokai]

This is quite true: but sort of irrelevant. Even the core developers on Python-dev have been seen to state on more then one occasion that they don't expect Python 3.0 to be the "standard" for a period of time that will stretch to years: one? three? The specifics don't exactly matter.

That's why they've done the releasing of Python 2.6 and Python 3.0 in parallel (although 3.0 was recently delayed a little, the development of each have been hand in hand); they fully expect to maintain the 2.x line for awhile, and are already talking of 2.7.

Each new iteration of 2.x will bring it closer to 3.0, and the third party modules will steadily become more and more available. Right now the IMHO biggest hurdle in the development of the modules for 3.0 is a lack of a serious conversion document from the point of view of the C internals. But they're even working on that.

3.0 seems to be, more then anything else, a work yet in progress. Even when it's released, its not fully expected to everyone will be converting their code over to be 3.0. They don't expect people to *really* start using it in a standard way until 3.1, 3.2 or so -- and whatever version of 2.x that will accompany it that people willll be converting from at that time, complete with additional features to help ease the transition.

Personally, I find the strategy for migrating Python to 3.0 ... comforting. I don't necessarily agree with *all* of the changes done to 3.0, but most I quite like. Since I have a massive codebase at work that's currently running on 2.x, a major/incompatible change to "fix" the language is something that alarmed me early on.

However, now I know that 2.x will be supported for quite awhile, and new releases will be made upon it to ease the way, I have a roadmap to follow that makes the burden significantly easier. Once we update our codebase to 2.6., I'll probably start slowly modifying things to activate more optional 3.x-isms, and by that time the myriad third party libraries will probably be supported.

2.6 brings a number of interesting features to us; and allows us to start working slowly towards migrating to the 3.0 world. This is a -very- well thought out migration plan, IMHO.

Anthony Baxter on Python 2.6 and 3.0

[xixax]

Anthony Baxter gave a pretty good talk on the implications at LCA 2008 earlier this year.

http://video.google.com/videoplay?docid=4264641260805367198&hl=en

Old news...

[pdxp]

3.0rc1 (beta) is already available and has been for some time now. The advantage of 2.6 is not as much its backward-compatibility but its ability to tell you exactly what needs to change (via runtime warnings) for 3.0 without actually breaking your code. I've been using both for months now, so this article isn't exactly hot news.

Re:i like python

[AlXtreme]

(Mind you, there online documentation could be better - PHP's site for example, is so much friendlier).

They're actually hard at work on that problem too. In addition to Python 2.6 being released, the Python documentation is now generated using Sphinx. See for example the new tutorial output. Big WTF the first time I saw it, but it's a decent improvement with more in the pipeline.