I have python 2.7 installed. I want to use python 2.4 to run python code. Is it possible?
Either directly use the Python 2.4 interpreter to run it, or modify the programs she-bang line to point to the interpreter you wish to use.
Note that there's many things in common use in recent python (any/all, the 1 if 2 else 3 syntax, as well as major stdlib and language changes) that may cause your program to experience difficulties.
It's also worth noting that a lot of the common 3rd party modules require at least 2.5 and some of those are even dropping that and only guaranteeing 2.6+ compatibility.
You can install Python 2.4 as well. Any of the minor versions, 2.4, 2.5, 2.6, etc. can live side by side.
Code you write for 2.4 will also run on Python 2.7, albeit that you may hit some deprecation warnings. If you are using the 2.7 interpreter to write 2.4 code, you'll need to be careful that you don't use syntax and modules that have been added in newer Python versions.
To see what has been added, look at the What's new documentation; there is a document for each minor version:
What's new in Python 2.5
What's new in Python 2.6
What's new in Python 2.7
You specifically want to look for syntax changes and for new modules to avoid.
There are a few things that can bite you. Some syntactic changes have happened since 2.4, so you may get syntax errors. The standard library is bigger in 2.7, so you may have some things missing. The docs generally lists the version of python when things were added, and can be great help in making sure things will run on different python versions. Generally, syntax and libraries are forward compatible, so if you have to support 2.4, I would write using 2.4 and things should work with 2.7. The same is not true in reverse.
Related
I'd like to upgrade to python 3.5, but I use legacy python 2.7 packages. Is it easy to run legacy packages in python 3.5? I have been under the impression that this isn't easy, but I did a few searches to see if I'm wrong and didn't come up with much.
I would expect there to be a multiprocessing package that allows standardized hand-offs between 3.5 code and 2.7 packages, allowing them to run independently under their own environments, but being somewhat seamless to the developer.
I'm not talking about converting my own code to 3.5, I'm talking about libraries that I use that won't be updated for or by me.
If you used the newer syntax supported by 2.7, e.g. around exceptions, and/or, better yet, worked with new features imported from __future__, you'll have much easier time converting your code to Python 3 (up to no changes at all). I'd suggest to follow this path first, for it can be trod gradually, without an abrupt jump to Python 3.
I suppose Python processes with different versions can interoperate, because object pickling format is compatible, and you can explicitly use a specific pickling protocol version on both sides to ensure that. I don't think multiprocessing packages on either side would be too useful, though. Consider using e.g. ZeroMQ as a more general solution.
Unfortunately there is no "nice" or automatic way of handling the processing of 2.7 code under 3.5 (that works perfectly).
You mentioned that you are concerned about libraries, not your own code - firstly, you'd hope that if they are under active development, they will be updated. If not, as you stated, then there is a possibility that they were written to be future proof. I've found some good ones are (e.g. google-api-python-client, e.g. https://github.com/google/google-api-python-client/blob/master/setup.py).
Failing that, the only way to upgrade is to fix all the syntax changes yourself. Most common ones I deal with are around 'print' and exception handling.
newb coder here
I have decided to dive headfirst into python and discovered there are different versions of python such as Python 3.2, 3.1 etc. Could someone please tell me if there is any difference? if I learn an older version would i have to re-learn a newer version or is it just an update to the libraries and stuff? Sorry if it seems trivial, I'm new to this
Check out the Python 3.2 release notes for specifics. You shouldn't notice any syntax differences or issues between 3.2 and 3.1, especially if you are just beginning. You shouldn't be worried about learning one then having to learn the other, they are basically the same.
Also, Python is very good about being backwards compatible, so almost everything you would do in 3.1 would work in 3.2
There are noticeable differences between Python 2.x and 3.x, where there are some changes in syntax and the way things work. Even then, if you "learned" Python 2.7, you'd be able to figure out 3.2 in a matter of minutes once you understand the differences.
I am just learning python on my ubuntu 8.04 machine which comes with
python 2.5 install. Is 2.5 too dated to continue learning? How much
of 2.5 version is still valid python code in the newer version?
Basically, python code, for the moment, will be divided into python 2.X code and python 3 code. Python 3 breaks many changes in the interest of cleaning up the language. The majority of code and libraries are written for 2.X in mind. It is probably best to learn one, and know what is different with the other. On an ubuntu machine, the python3 package will install Python 3, which can be run with the command python3, at least on my 8.10 install.
To answer your question, learning with 2.5 is fine, just keep in mind that 3 is a significant change, and learn the changes - ask yourself as you code, "how would this be different in 3, if at all?".
(As an aside, I do wish Ubuntu would upgrade to 2.6 though. It has a nice compatibility mode which tries and points out potential difficulties. But python is in such big use on a modern Linux distro, it can be a difficult change to make)
Here's an article describing 2.6 -> 3's changes
Python 2.5 will be fine for learning purposes. In the interest of learning you will probably want to look into the differences that python 3.0 has introduced, but I think most of the Python community is still using Python 2, as the majority of libraries haven't been ported over yet.
If your interested in 2.6 here is a blog post on compiling it on Hardy, there may even be a package for it somewhere out there on the internets.
Follow up, if there is a package I'm not finding it. Self compiling is pretty simple for most things, though I've never tried to compile Python.
I don't think it is 'too dated' to use, but there are some really nice features in python 2.6 that make it worth the update. This article will give you the details. As long as you have control of the machine, it is worth it.
I don't have any statistics but my impression is that Python 2.5 is the version most in use today. It is certainly not "dated" - I still use Python 2.5 and I expect that I will be using it for weeks or months yet to come.
If you have Python 2.6 available, though, I would suggest upgrading, as it's still fairly similar to Python 2.5 but will put you in better position for using Python 3.
Also, right now the 2.x branch is the most supported one, so I would also say that it's a good reason to start with that version.
And when the moment comes, you can always switch to Python 3.
Python 2.5 is fine. There are still plenty of people on Python 2.4 and 2.3.
One thing to keep in mind about python 2.6 is that some libraries may not work. Numpy comes to mind..
If I learn python 3.0 and code in it, will my code be still compatible with Python 2.6 (or 2.5 too!)?
Remarkably similar to:
If I'm Going to Learn Python, Should I Learn 2.x or Just Jump Into 3.0?
No, 3.x is largely incompatible with 2.x (that was actually a major motivation for doing it). In fact, you probably shouldn't be using 3.0 at all-- it's rather unusable at the moment, and is still mostly intended for library developers to port to it so that it can be usable.
Python 2.6 and Python 3.0 are very compatible with each other. There honestly aren't very many differences between the two. At this point, third-party library support is far better for the 2.x series (last I checked, a few libraries I use hadn't been updated from 2.5, but going from 2.5 to 2.6 is just a recompile, but 2.6 to 3.0 for C-level stuff is a real pain).
Just start learning 2.6. The infrastructure is there now, and there's plenty of help for when you finally want to move to 3.x. 2.x is not going away: there will be a 2.7 release at some point, so you're not going to be out of luck if you learn 2.6 now.
It would be easier to use 2.6 right now because most external libraries are not compatible with 3 yet.
NO. Python 3 code is backwards incompatible with 2.6. I recommend to begin with 2.6, because your code will be more useful.
In most cases it's not required anymore learn to Python 2 along with Python 3 for the following reasons.
Python 2.7 reached the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 is no longer maintained, and dedicating effort to learning it doesn't make sense anymore for most people. Also there may be problems installing some Python 2.7 packages that don't have any problems installing them in Python 3.
Python 3 is the best way to learn Python for the first time, because it's easier for beginners to understand than Python 2.
If I was going to start an open source project using Python what version should I use to ensure that the vast majority of users can use it on their system?
I'm the kind of person who quickly jumps to the next version (which I'll do when Python 3 comes out) but many people may be more conservative if their current version seems to be working fine. What version would hit the sweet spot but still allow me to enjoy the newest and coolest language enhancements?
As python is in kind of an transition phase towards python 3 with breaking backward compatibility I don't think it is a good idea to go python 3 only. Based on the time line there will be at least one or two following releases of the 2.x series after 2.6/3.0 in october.
Beside not having python 3 available on your target platforms, it will take some time until important external python libraries will be ported and usable on python 3.
So as Matthew suggests staying at 2.4/2.5 and keeping the transition plan to python 3 in mind is a solid choice.
I've not seen a system with less than 2.3 installed for some time. Mostly 2.4+ is installed by default for most OS I use now. 2.3 is just on an older Solaris machine. Linux distros tend to have 2.4+, as does OS X.
IIRC, 2.4 has a lot of the features 2.5 does, but usable only with
from __future__ import *
You can use different versions of python on each machine.
Coding something new, I would not use anything less than python2.5. You can do apt-get install python2.5 on stock debian stable.
For windows, don't really worry about it. It's very easy to install the python2.5 msi.
If the users can't be bothered to do that, you can deploy an executable with py2exe (so simple) and build an installer with inno setup (again simple) then it will behave like a standard windows application and will use its own python dlls, so no need to have python installed.
Like Peter said: keep in mind the transition to 3.0 but don't build on it yet.
Python 2.3, or 2.2 if you can live without the many modules that were added (e.g. datetime, csv, logging, optparse, zipimport), aren't using SSL, and are willing to add boilerplate for True/False.
2.4 added decorators. generator expressions, reversed(), sorted(), and the subprocess and decimal modules. Although these are all nice, it's easy to write Pythonic code without them (assuming that your project wouldn't make heavy use of them).
2.5 added with, relative imports, better 64 bit support, and quite a bit of speed. You could live without all of those easily enough.
2.6 isn't released (although it's very close), so while it might appeal to developers, it doesn't have the compatibility you're after.
Take a look at the release notes for 2.3, 2.4, 2.5, and the upcoming 2.6 (use http://www.python.org/download/releases/2.Y/highlights/ where 'Y' is the minor version).
FWIW, for SpamBayes we support 2.2 and above (2.2 requires installing the email package separately). This isn't overly taxing, but the 2.3 additions are useful enough and 2.3 old enough that we'll probably drop 2.2 before long.
If the project is going to be mainstream and will be run on Linux the only sensible choise is 2.4 - just because it is a pain to get anything else installed as default on Enterprise Linuxes.
In any case, any modern OS will/can have 2.4 or newer.
You should use Python 2.7, the final major version of Python 2.
Python 3.x currently has limited 3rd-party library support, and is often not installed by default. So you are looking at the 2.x series.
Python 2.7 is essentially fully backwards-compatible with earlier 2.xs. In addition, it can give deprecation warnings about things that won't work in Python 3. (Particularly, it will pay to maintain unit tests, and to be pedantic about Unicode- vs. byte-strings.) The warnings will force you to write good code that the automated 2to3 tool will be able to translate to Python 3.
Guido van Rossum officially recommends maintaining a single Python 2 code-base, and using 2to3 together with unit testing to produce compatible releases for Python 2 and 3. (Since PEP 3000 was written, Python 2.6 has been superseded by 2.7.)