I'm working on my first Python-based program. I would like it to be as maintenance free in the future as possible and I was wondering if this could be a problem as Python is updated. I'm using 2.7.2 currently, but when 3 becomes standard what could happen to my program? Will it likely stop working on a system installed with Python 3 and will it be impractical to have the user install an older version of Python? I assume 2.7.2 won't be maintained indefinitely, and I wouldn't think newer versions of Python would run my program successfully. Sorry if this seems like a newb question; I'm used to working with compiled languages.
Not to stray too far off topic, but would it be better to use Lua in this case?
Will it stop working - that depends on how the program is being run. If the system has both versions installed and you ask to run against Python 2, then it'll continue to work. If you don't explicitly ask to run against a certain version, and it's not there, then it'll probably fail.
Lua offers you no solutions here - if you rely on a system-installed Lua and that Lua becomes incompatible in the future, you're stuck. Think of your scripting language as a dynamic library - if the user has the right version, they're ok, and if not, they don't, just like with C/C++ apps.
If you're deploying to Unix-like platforms, I expect they will support Python 2 for at least another 5 years, maybe 10.
If you're deploying to a Windows platform, you usually package up the relevant version of Python as part of your app.
So the problem is unlikely to be as significant as you fear.
It will take a very, very long time until Python2 will die.
Python2 code will most likely require modifications to run with Python3 (there's the 2to3 tool to help with migrating though), but with all the libs out there which are for python2 it will take years until py2 dies - so you don't really have to care about it right now. Besides that, I believe as long as enough people are using Python2, a version will be kept up to date with fixes.
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I read somewhere you could run python without an OS. How would I do this? Would I need to compile it? Can I run it raw? And if I did need to compile it, what tool would I use and what format would I compile it to?
As far as I know there's not really any way to do this easily but I could be wrong. There are "portable" versions of python but these are operating system dependent. I think what you're referencing is some guys at PyCon managed to run python from the GRUB Bootloader. Your best bet would be installing some minimalist Linux distribution, with essentially only Python and some core packages required to run. The problem is that there's a lot of types of hardware out there, all with their own drivers and assembly language. Python can work as a low level language when you need it to but it seems like configuration would be a nightmare. I haven't looked into it super thoroughly but it seems difficult and impractical. Having an OS above python gives you access to the package managers IDEs and compilier options that make python worth using.
yea that's one of the options, pretty much all the "light" distros will be similar, if you want more to try out try here. Not sure why you're worried about speed though, if you're having speed issues it's far more likely to be the IDE you're using or your code bogging down the computer, not any sort of compiler issues.
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.
I have some rather large code I've written and tested to work with the 2.7.3 version of python available in my elementary OS 0.2 system (based on Ubuntu 12.04)
My code is hosted on Github and I'd like to know if it works on newer versions of python up to 3.x.
Is there some way to do this automatically or with as little hassle as possible?
It's unlikely that your code will work automatically unless it's some very simple script because many of the standard Python operators and methods changed. For example, the print statement becomes the print() method, and that will become a syntax error when you try to run the code.
If you're willing to take the time to set it up and install other version of python, you can use PyEnv to install multiple versions of Python to test your code with. It's very similar to Ruby's RVM if you've used that. While it's not an automated method of testing if your code will work, and it does require some setup, it is a way that you could test your code on multiple versions of Python. Once it is setup, you can continue to use it for your other Python projects as well.
In addition to PyEnv, you can take inspectorG4dget's advice from the comments and use Python's automated version 2 to version 3 code translation. Since it is unlikely that your code will work immediately in version 3 due to changing syntax of keywords and standard methods, you can use that tool to translate your code without too much effort.
Is it possible to deploy python applications such that you don't release the source code and you don't have to be sure the customer has python installed?
I'm thinking maybe there is some installation process that can run a python app from just the .pyc files and a shared library containing the interpreter or something like that?
Basically I'm keen to get the development benefits of a language like Python - high productivity etc. but can't quite see how you could deploy it professionally to a customer where you don't know how there machine is set up and you definitely can't deliver the source.
How do professional software houses developing in python do it (or maybe the answer is that they don't) ?
You protect your source code legally, not technologically. Distributing py files really isn't a big deal. The only technological solution here is not to ship your program (which is really becoming more popular these days, as software is provided over the internet rather than fully installed locally more often.)
If you don't want the user to have to have Python installed but want to run Python programs, you'll have to bundle Python. Your resistance to doing so seems quite odd to me. Java programs have to either bundle or anticipate the JVM's presence. C programs have to either bundle or anticipate libc's presence (usually the latter), etc. There's nothing hacky about using what you need.
Professional Python desktop software bundles Python, either through something like py2exe/cx_Freeze/some in-house thing that does the same thing or through embedding Python (in which case Python comes along as a library rather than an executable). The former approach is usually a lot more powerful and robust.
Yes, it is possible to make installation packages. Look for py2exe, cx_freeze and others.
No, it is not possible to keep the source code completely safe. There are always ways to decompile.
Original source code can trivially be obtained from .pyc files if someone wants to do it. Code obfuscation would make it more difficult to do something with the code.
I am surprised no one mentioned this before now, but Cython seems like a viable solution to this problem. It will take your Python code and transpile it into CPython compatible C code. You also get a small speed boost (~25% last I checked) since it will be compiled to native machine code instead of just Python byte code. You still need to be sure the user has Python installed (either by making it a pre-requisite pushed off onto the user to deal with, or bundling it as part of the installer process). Also, you do need to have at least one small part of your application in pure Python: the hook into the main function.
So you would need something basic like this:
import cython_compiled_module
if __name__ == '__main__':
cython_compiled_module.main()
But this effectively leaks no implementation details. I think using Cython should meet the criteria in the question, but it also introduces the added complexity of compiling in C, which loses some of Python's easy cross-platform nature. Whether that is worth it or not is up to you.
As others stated, even the resulting compiled C code could be decompiled with a little effort, but it is likely much more close to the type of obfuscation you were initially hoping for.
Well, it depends what you want to do. If by "not releasing the source code" you mean "the customer should not be able to access the source code in any way", well, you're fighting a losing battle. Even programs written in C can be reverse engineered, after all. If you're afraid someone will steal from you, make them sign a contract and sue them if there's trouble.
But if you mean "the customer should not care about python files, and not be able to casually access them", you can use a solution like cx_Freeze to turn your Python application into an executable.
Build a web application in python. Then the world can use it via a browser with zero install.
As a small-time Python package writer (cobs, simplerandom), I'm wondering what Python versions I should support.
I've heard anecdotally that Python 2.5 is still in use on enterprise type servers. So I thought 2.5 was the oldest that needed to be practically supported, here in 2011.
However, I saw this blog in which the author says he's still using 2.4. From memory, I saw an e-mail on the PyCrypto mailing list saying they aimed to keep support going back to 2.2 if possible.
Of course, then there's Python 3.x which is slowly gaining momentum. It would be good to know who is using that.
Then, there is also Jython and Ironpython, and I have very little idea about them.
Is there any concrete and up-to-date Python installation/usage data available to enlighten us? Is there any "best practices" or other advice for what versions/flavours of Python a package writer should aim to support?
I think that this is a problem that's simply inherent when developing any software. Anyone could be running any version and would need support for that version (I wonder how many people are still running Windoze ME out there? ;)). Personally, when developing libraries, I'll support only support the current version+. If for no other reason, because I'm only one person and I don't have a team.
Having said that, I'd stick my packages up on github and take patches from anyone who wants support for previous versions (and is willing to put in the work).
Edit:
I've found that a good rule in software development (especially packages) is develop only for what is needed, not what you think might be needed. In other words, get it working for whatever version of Python you're running (or is dearest to you) and then take support requests if you want to implement them yourself as people need them.
I have servers that run Python 2.3. :-)
But no, you don't need to support it. Most servers like that are just running, and do not get any new modules installed.
When creating a new module today, 2.6, 2.7, 3.1 and 3.2 is the versions to support. For existing modules you can ask your users. :-)
You should support the latest of the 2.x series (2.7 as of now) and 3.x (3.2 as of now). Unless you have a specific need for supporting older versions, I don't think you need to go there.
As for alternate implementations like IronPython and Jython, you should do that only if needed. It can be time consuming (although perhaps educational) to support you app for all these implementations.
As a side node, to test your app on multiple versions/implementations of Python, I recommend tox.