Ok, let me add another long post to this conversation... hopefully you have enough patience!! This is probably known stuff for some of you, but I'm sure some others will learn something! I kindly ask you to try to go through all this post, I think it will be worthwile.
Short and not so important things first: why can't I get method suggested by Jason to get Python integers in SAGE work from the notebook? I mean: import quantities as pq res = 10r*pq.ohm works in sage (run from the command line), but not from the notebook! I get the same error, and I also get value = 10 type(value) <type 'sage.rings.integer.Integer'> value = 10r type(value) <type 'sage.rings.integer.Integer'> But from sage command line I correctly get type(10r) = python integer! Why is that? Let's go to the units package discussion. I had a look at this (not so new) discussion in the enthought mailing list: https://mail.enthought.com/pipermail/enthought-dev/2007-September/009125.html Let's consider the "units" package in enthought the equivalent of the "father" of "quantities", hoping that I understood everything correctly. Let me cite the author of "quantities": <Citation> I've been working on an ndarray subclass which could unify these two packages. Unit conversion is handled by UDUnits, which is compatible with the terms of the BSD. I've done some preliminary unittesting and things look good on both windows and linux. I'm waiting for numpy-1.2 to be released so I can use the incorporated nose-based unit-testing framework to continue writing unittests. The package is available at http://dale.chess.cornell.edu/chess-wiki/Quantities . The package only depends on numpy, and does not require Traits, so I was thinking it might be better to continue development as a scikit and decide later where and how to incorporate it into enhought, scipy, numpy, or none of the above. </Citation> In the enthought mailing list, they claim that: "The units package is very stable, but perhaps lacking in documentation.". Which is pretty good. Then, another person in that thread states: "Have you guys look at scientificPython's units ? I use them through ipython shorthands and they are pretty good. It won't run on your system because you don't have the required modules (well, I could make it run, but it's not worth it), and it needs to be ran through ipython, with the "physcis" profile". So I discovered this (reference: http://modular.math.washington.edu/home/jvoight/sage-2.10.2/local/share/doc/ipython-0.8.1/manual.pdf ): "The module PhysicalQInput allows a simplified form of input for physical quantities with units. This file is meant to be used in conjunction with the PhysicalQInteractive module (in the same directory) and Physics.PhysicalQuantities from Konrad Hinsen’s ScientificPython (http://dirac.cnrs-orleans.fr/ScientificPython/)." So, it seems that PhysicalQuantities (together with the "physics" profile of iPython, which could be maybe used in SAGE, if needed??), is pretty much a standard thing for Python (which seems VERY good!), so let me investigate why these enthought guys needed something different (reference: reply in the same previous mailing list): "enthought.units provides a similar mechanism, if thats the route you want to go. The reason we don't typically use the package that way is because unit conversions because if forces explicit unit conversion. Say we were to send a probe to mars, and somewhere in our code we used metric, and other places we used imperial, we would have to know at what points the two unit systems required conversion. Otherwise, the probe burns up in the atmosphere... Some of our apps have data in multiple unit systems, so having the automatic conversion is a big plus, but this may not be true for every app." I have to admit I totally agree with this guy, so I am basically going for enthought's approach! But, wait a minute, what if I install SciMath (the enthought package) I downloaded last night? Well, the result is not that good, because you basically need a lot of other enthought stuff to let enthought.units work: from enthought import units Traceback (click to the left for traceback) ... ImportError: No module named util.resource The problem is that you have to modify "units" from SciMath to let it work without the enthought util environment. I'm not that into doing this. To summarize stuff: 1) the Python standard seems to be iPython + "physics" profile + Scientific Python 2) the Enthought suite uses two different packages, but it "seems" that the most used is "units", and one big plus is the ability to mix together (as they say, I was not able to verify it) different units of the same physical quantity and let the "decorator" do the translation job to some preassigned standard for that quantity 3) the Quantities package has been developed as a refactoring and joining of the two Enthought package, although this units mixing (claimed as possible in Enthought) seems not natively supported (if I try to add 10 inches and 10 meters I get an error... I can't even add meters and centimeters!) which is not good. A good plus about "quantities" is that it seems actively developed, as I can see from their active mailing list: https://lists.launchpad.net/python-quantities-developers/threads.html I can see that in the middle of January they were thinking about their timeline, since they presented something to the SciPy community recently, and had some good feedback. They are currently discussing about being almost ready to present something to the numpy community, so they seems satisfied with what they have now: https://lists.launchpad.net/python-quantities-developers/msg00057.html Don't you think it would be REALLY useful for us to try to discuss with them (I'm sure some of you guys, can represent this SAGE community much better than I do), and to ask them if they are willing to work with us on making quantities compatible with one of our symbolic packages? They seem pretty experienced about this package, seem willing to improve their work, and this is (in my opinion) going to be a VERY BIG PLUS for SAGE!! I mean, I don't think anything out there is actually able to manage symbolics and units at the same time, do you? I'm very eager to see your comments, hoping that you get my passion and enthusiasm! Best regards Maurizio --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-devel@googlegroups.com To unsubscribe from this group, send email to sage-devel-unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
