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Beginner Learning Python: 2.7 or 3?
56 points by jhacks on Jan 1, 2012 | hide | past | favorite | 24 comments
I have taken the dive to learn Python (currently only experience I have is HTML, CSS, JavaScript, jQuery) and I'm using Learn Python The Hard Way.

However, this has me using Python 2.7 and I know that this is the last of Python 2.x and Python is what I might need to know going forward.

Should I look somewhere else to learn (I've gotten just about halfway through LPTHW) or stick through this? I guess it depends how different they are and if it's worth learning Python 2.7 if I'll just be unlearning and relearning certain aspects.

What should I do?



There's very little to unlearn; go with 2.7 and move over to 3.x with the rest of us when we all get around to it, if we ever do ;)


> if we ever do

No kidding... Here we are, how many years after the release of Python 3? And still, there are many libraries that have yet to be ported to Python 3. These deficiencies make Python 3 an impossible choice for some tasks. The slow adoption of Python 3 is not without reason as many have pointed out, although Armin Ronacher's recent blog post[1] stands out as one of the better illustrations of the frustrations with Python 3. I have to say, as a Pythonista, I am worried about Python. I wonder if things will become increasingly fragmented...

[1] http://lucumr.pocoo.org/2011/12/7/thoughts-on-python3/


The adoption rate is expected, people should stop complain about the python3 situation when it's not that bad.

http://sayspy.blogspot.com/2011/01/my-semi-regular-reminder-...


It looks like a patch for Django was just finished relatively recently.

For what it's worth, based on my experience with Ruby 1.8/1.9 in Rails, which is a smaller language change that Py2=>Py3, it will take years and a lot of community work before Django on Python 3 is a plausible solution.

Rails officially supported Ruby 1.9 as early as Rails 2.3 (which was released in February 2009), but a large number of commonly used packages weren't really working for some time after that. Additionally, we made a number of mistakes our initial Ruby 1.9 support (in Rails 2.3), which we corrected in Rails 3.0.

My guess (again, based on my experience with false starts in Rails) is that merging the patch in question will take a while, and that it will require some time after the patch is initially merged before people consider Py3 a valid target for Django apps.


I don't know Ruby, but was the difference between Ruby 1.8 and 1.9 as drastic as the change between Python 2.7 and 3.0? Programs written in Python 3.0 are not backwards compatible. Is it the same with programs written in Ruby 1.9? I'm really asking -- I don't know the answer.


Ruby did us a big favor and made it possible to implement something like Rails in a way that switched between Ruby 1.8 and 1.9 at runtime. There are no changes to the 1.9 parser that cause it to puke on 1.8 syntax.

My understanding is that in Python, you need to use the 2to3 tool for a program of any non-trivial size to have a single codebase that targets both. Please correct me if I'm wrong, as I'm only picking this up by osmosis with the Python community.

Ruby 1.9 is also significantly more runtime compatible with Ruby 1.8 than Python 3 is with Python 2. For example, the object model and semantics for creating classes and object is entirely unchanged between Ruby 1.8 and Ruby 1.9. The Unicode change took great pains to remain compatible with programs using BINARY data for ASCII-only characters, for instance (I personally believe that this was a mistake going forward, but it results in better-than-expected backwards compatibility with Ruby 1.8 programs mixing source code and external ASCII-only data).

As a result, even though Python 3 was released around the same time as Ruby 1.9.1 (the first stable Ruby 1.9 release), the Ruby community is much further along the adoption curve than Python is.


Sorry for the delayed response -- I do want to respond to several points. First, you're sort of correct that you need the 2to3 tool for a program to target Python 2 and Python 3. There are certain programming techniques (such as "from __future__ import *) that will allow you to write you code in such a way that it will run on both Python 2 and 3, although I've not used these on any project of size. But if you wrote your code using plain vanilla 2.x, then you'd need to use the 2to3 tool, although again I've not used it myself and have heard mixed reviews. Unicode is probably the biggest change from Python 2 to 3 that introduces incompatibilities, although I think there are tricks for dealing with that as well. I like Ruby's approach to Unicode based on what you described. Why do you think this is a mistake? I expect you are correct that Ruby is much further along in moving from 1.8 to 1.9, because it sounds like Ruby has handled the upgrade path well (to be honest, I'm not sure Python has).


If you used the ruby 1.9 syntax then it wouldn't be. However, ruby 1.9 still supported the old syntax, so libraries in 1.9 could still be used with 1.8. There wasn't "one right way" to do things in ruby.


I thought I was on Stack Overflow for a moment, because this question always seems to come up.

http://stackoverflow.com/questions/5478518/python-2-or-pytho... http://stackoverflow.com/questions/170921/to-learn-python-2-... http://stackoverflow.com/questions/1222782/should-i-start-wi... http://stackoverflow.com/questions/2090820/what-version-of-p...


Stick with Python 2.7 at the moment; there are many reasons for this which I will not go into. But, later on if the community/if you decide to switch more towards Python 3, then you will not be 'unlearning' much.

I recommend LPtHW and then Dive into Python. After going through those two books you will have a really goo grasp on the Python Programming Language. After which start coding and (possibly) get involved in some Python-based open source project (or at least study the code a bit).


May I also recommend How to Think Like a Computer Scientist, Python version, 2nd edition? This edition uses Python 2..

I agree with everyone recommending Python 2.7, but do be sure you use the latest iteration of the Python 2. series. Python 2.4 and even 2.5 are missing some great new features, many of which show up in Python 3.0. To me, Python 2.7 is the best of both worlds -- all of Python 2.x's great features and familiarity, combined with most of the real needed changes in Python 3.0.

I totally agree with Armin when he writes that there should be a Python 2.8 and 2.9. A better upgrade path is needed.


Thanks for all the replies everyone! It definitely seems like it'd be worthwhile just going through and learning 2.7 then and using related libraries to create what I want (once I've learned and am able to do so).

However, this has me thinking. It seems like Ruby (and related frameworks, like Rails) don't have the backwards-compatibility issue that is seemingly plaguing Python?

The newest version of Ruby was easily adopted (compared to Python 3) as it remained backwards-compatible. Even upon researching the next evolution of Ruby (2), it seems that it won't be huge leap and, again, will remain backwards-compatible.

My question is... if I'm looking to start building a website now and use Python 2.7 (and likely Django), what would I do when the time comes and Python 3 is really the go-to version?

Would I need to rewrite the code entirely? Will the older code ever become compatible or easily transitioned?

It seems like Ruby would be the better choice to avoid possible fragmentation issues?

I could be entirely wrong here though. So, please, if someone could help me with this, that would be great. I went through some of Learn Ruby the Hard Way. And I'm willing to switch over to Ruby.

I like them both in different ways in terms of syntax/readability. But I don't know enough to really make a decision beyond that.

But this Python fragmentation between 2 and 3 makes me worried. I'd feel safer choosing to learn Ruby. I don't know though.


Once you learn Python version:X, you won't care about what version you're using.

Forget about the version crap and focus on learning.


Keep going. Until the important libraries catch up, you should be using 2.7 for doing most projects at the moment. You won't have wasted much learning in the mean time.

Happy New Year.


Keep going. Until the important libraries catch up, you should be using 2.7...

It's true some important Python libraries still only work on 2.X. And, as someone who's been writing the majority of my real-world production code in Python 3 for over nine months now, I've found it's not necessarily a barrier.

So, for those of you not coding in 3 but would like to, what are these missing "important libraries"? What Python libraries do you need, that do not have quality ports to Py3K yet?


As cschmidt pointed out, Django is the big one, but here is a list of the popular apps/libraries and whether or not they are 3.0 compliant.

http://python3wos.appspot.com/


For me, Django.


From Learn Python The Hard Way: http://learnpythonthehardway.org/book/ex0.html

A programmer may try to get you to install Python 3 and learn that. You should tell them, "When all of the python code on your computer is Python 3, then I'll try to learn it." That should keep them busy for about 10 years.


Is the goal here to learn how to write code in Python or to learn the specifics of each version of the language? If the goal is to just learn Python, I don't think it really matters which version you learn since the general basics of the language are pretty much the same between versions. In other words, a for loop is still a for loop.

Asking Google came up with this link: http://wiki.python.org/moin/Python2orPython3

I'd personally start with 2.x so that you can understand the history of Python and then make sure to have an understanding of what is changing in 3 via links like this: http://docs.python.org/py3k/whatsnew/3.0.html

Finally, if this is for a job, I guess one thing would be to see what the requirements of the job are. If you need to use Python 3 for your job, your best bet is probably to learn Python 3. =)


The difference between 2.7 and 3 is, to be honest, nothing big in terms of programming. I use both mostly without noticing the difference, because some libraries are still on old versions. For now, use import __future__ to help ease the transition and don't stress.


If your code heavily uses unicode texts, it will be easier to start with python 3, because all the iterators word on wide-chars instead of byte ones, and you don't have do some magic to handle them properly.


2.7 if you want to release anything AND consume other libraries. 3 if you never intend on using other than a learning exercise or will write everything from scratch.


What versions of python are on your machine?

My MBP (leopard -> snow leopard -> lion) has python versions 2.5, 2.6, and 2.7 (and there's a nice way to change the default python version). I fully suspect python3 is not there by default.


New projects should go with Python 3, if possible. But really, the two languages are not very far apart. Do whichever if you are just learning and want to make small temporary things.




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