Mailman 3 July 2001 - Edu-sig

More spillover re the division PEP
by Kirby Urner July 26, 2001

July 26, 2001

From: Kirby Urner <urner(a)alumni.princeton.edu> Newsgroups: comp.lang.python Subject: Nostalgia for the present (re the infamous PEP) Date: Wed, 25 Jul 2001 10:10:27 -0700 I tell ya, given all the uproar over // vs /, I'm already nostalgic for the good ol' days (these are them), when / left it up to its arguments to determine the type of the result. In so doing, it followed the same type conventions as the other arithmetic operators: Python 2.1.1 (#20, Jul 20 2001, 01:19:29) [MSC 32 bit (Intel)] on win32 Type "copyright", "credits" or "license" for more information. IDLE 0.8 -- press F1 for help >>> type(1+1) <type 'int'> >>> type(1+2.) <type 'float'> >>> type(1*2) <type 'int'> >>> type(1*2.) <type 'float'> >>> type(1/2) <type 'int'> >>> type(1/2.) <type 'float'> But now we're gonna have: >>> type(1/2) <type 'float'> The programmer doesn't have to do any casting, as type conversion when returning a result is automatic. def velocity(miles,hour): return float(miles)/hour In the new regime, / is guarenteed to return a float, and // is guarenteed to return and int, no matter what the numeric args. This puts / in a new category among the arithmetic operators: the operator itself ensures type of result, not the args. But that's because / *is* special in some ways: + - and * are all closed in Z (integers), but the integers form a ring, not a group, with respect to + and *, such that the multiplicative inverse of j -- i.e. 1/j or j**(-1) -- is not in Z unless j=1. This is what's driving / to be coercive, and to differentiate from //. My own view is there's a lot of rationale for either way of doing it, with the fact of the initial design choice weighing heavily on the side of keeping it the way it is. I prefer that newbies learn that type(int/int)==int and that pro programmers sometimes "get burned", and that Guido not be apologetic or remorseful for this initial design choice -- nor for making Python case-sensitive (a perfectly reasonable decision as well -- it's gotta be one way or the other, and there's plenty to say in favor of either). To take a page from our favorite giant: It's not a wart (bug), it's a feature. Kirby

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Seeking Technical reviewers for Python
by Kristen_Blanco＠prenhall.com July 24, 2001

July 24, 2001

am writing from Prentice Hall publishing and I am seeking reviewers for an upcoming publication. We are one of the largest college textbook publishers in the US. We are publishing a book entitled "Python How to Program" by Harvey and Paul Deitel. They are premier programming language authors, with the best-selling C++ and Java books in the college market place. More information on their suite of publications can be found here: http://www.prenhall.com/deitel We are presently seeking qualified technical reviewers to verify that the Deitels' coverage of Python in their forthcoming book is accurate. In return, we are offering a token honorarium. Might you be willing to participate? If not, could you perhaps suggest a colleague? If you are interested, or have any questions, please contact my colleague, Crissy Statuto, at Crissy_Statuto(a)prenhall.com Thank you in advance for your assistance and consideration. Sincerely, Crissy Statuto Crissy Statuto Project Manager, Computer Science Prentice Hall One Lake Street- #3F54 Upper Saddle River, NJ 07458 Tel: 201-236-6695 Fax: 201-236-7170 Email: crissy_statuto(a)prenhall.com

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Re: PEP0238 lament
by Arthur Siegel July 24, 2001

July 24, 2001

Kirby writes - >In the meantime, I think I should exert greater effort >to learn both Scheme and Eiffel. I'd also like to learn >OCaml while I'm at it. Travel broadens, no doubt. ART

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Re: PEP0238 lament
by Arthur Siegel July 24, 2001

July 24, 2001

>Well, I'll see what I can do. In the language there are (at least) >two distinct things we might want to do when "dividing" A and B: > (1) split A up into B parts > (2) find how many B's fit in an A etc... The well intentioned response I think only points out the problem more. You don't seem to understand that my point is that, within reason, I do in fact understand all this fairly well. Anyone else of normal intelligence should be able to also. My further point is that there is a lot about programming that I do find difficult. The difficult parts. Which is why I keep feeling the techies among you have lost touch with common sense. Almost comically. The easy stuff is easy, the hard stuff is hard. It's not that difficult to separate which is which. Which is why I am always amazed at what gets reported - and taken seriously - as significant. Will I have any problem with // and / - using them appropriately Doubt it. Can I handle case sensitivity any way you give it to me. Cake. Why is two years of discussion going on as if someone like myself is not fully representative. I simply have no reason to believe I am not. And will scrutinize carefully any evidence which contends otherwise. Should major design decisions for a professional language be made on anecdotal reports from ???????? sources without a hard look at their context and meaning. Not in my opinion. Do I believe the change is a significant enhancement on behalf of the newbie. Not in the least. Will Python be a better language after it is done. I don't have a good basis to disagree with that assertion. And none of these statements seem a bit contradictory to me. >A good example of (1) is float division, and the cannonical example >of (2) is "int division", aka "div". These are DIFFERENT THINGS. >For instance, if you are implementing a sort algorithm, you may >well want (2) in a place where (1) will never do! On the other >hand, if your program is performing CAD drawings, then (1) is >probably the meaning you need. Note that (2) often makes most sense >with integers (especially since it always gives out an integer), >while (1) may make sense with floats, rationals, fixed-position >decimals, as well as various other numerical types.

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Computer science without all that "heavy math" stuff...?
by Danny Yoo July 24, 2001

July 24, 2001

[First, I have to apologize in advance; I think this post a rant. Now that I've written it, it really doesn't touch on Python, although it hints at the role of CP4E.] Recently, the Potomac Tech Journal published an article: "Universities aren't serving the IT workforce" http://www.potomactechjournal.com/displayarticledetail.asp?art_id=48819&sec… which I found offensive in the article's attitude toward computer science education. The article seems to argue that CS education should cater more towards the IT workplace, removing prerequesites that are not "needed by business". He uses his son as an example of how CS education has failed him. """My son now attends Boston College, majoring in business and computer science. After one semester of computer science, he decided he didn't care for the heavy math concentration, in spite of the fact that he loves to write code and has done so for several years. Another IT worker lost.""" My argument with the article is that it assumes that the charter of a computer science education is to make good little IT tech workers. It seems to ask "What good is education?" Didn't Pythagoras or Euclid have to deal with this attitude once? If CP4E ever becomes widely implemented, will educators also have to defend what they teach on the basis of direct application? I don't think application training is what computer science should primarily be about. If one wants to find a place to get IT training, the trade schools are simply a more appropriate place. On the other hand, computer science should expose students to ideas as well as techniques. In short: it should be dense but filling. Furthermore, the article's view of computer science completely ignores the role that mathematics plays in CS. For example, computer graphics uses linear algebra and artificial intelligence uses logic --- both would be empty calories without the technical content. These two fields are significant, even in a business setting, and it seems a very shallow view to restrict an CS education to "IT". The author concludes with: """Our colleges and universities are supposed to be training the workers of the future. Despite the current soft economy, well-educated technology workers will be in demand for many years to come, so institutions of higher education would be wise to make curriculum adjustments now in order to meet this long-term demand.""" If direct applicability is the article's argument, then even the author must admit that some "theory" is necessary to create a well-educated and effective workforce. Still, even with the shallowness of the argument, the article still touches on an attitude that seems common: what good is education if it cannot be applied?

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PEP0238 lament
by Arthur_Siegel＠rsmi.com July 23, 2001

July 23, 2001

Before going further in attempting to contribute to the discussions of Pep238 (or case sensitivty) allow be to present my credentials. None, to speak of. Except that I've been through the program. Guido's program. His language. His environment. His tutorials. I think with some success. Participate little on python-list, because much of what goes on is over my head. But on the question of learning programming with Python - as I mention, been through the program. Here the issues are under my nose, not over my head. I particpate actively on the edu-sig list, because I understand my success could be other's success. Am a big supporter of Guido's CP4E ideals. Yet despite the gratitude I try to keep in mind, I clash consistently with Guido on CP4E - sometimes in unpleasant ways. Can only hope he appreciates at some level that I bring some passion to the table on some common goals. Because that clash now spills over to the Python list. Since I have convinced myself that not only do I object to the rationale and evidence gathering behind the integer division change - I am going to step up and be arrogant enough to say that I am against it as a design feature, in light of the only aspect of Python design about which I would dare to speak - CP4E goals. 3 / 4 = 0 3.0 / 4 = .75 Something important is going on here. I have a decent understanding of what that is. Enough to get me by in the real world. I came to It - having already understood that I would only get so far if I expected it all to come to me. That reckoning has been put off an hour ot two for the Python 2.2 learner, with a measurable cost. Pity for the Python2.2 learner. Quite well realize that I am not saying anything that hasn't been said before on the issue. But disappointed to never have heard the counter argument from Guido - what put the issue over the top for him? If I was told that experinced programmers might appreciate this change for any possible reason - I'd be quiet as a mouse. Since I remain convinced that the single most important factor for Python's acceptance as an educational language is the growth of its acceptance as a professional language. It will be interesting to see where Guido chooses to draw the line on the thought process that lead him to his integer division conclusion. Which is the real issue - the integer division thing, stand-alone, not likely to be a deal breaker for anyone. Like to believe that there is more real world thinking than Guido chooses to share publicly. Alternatively, I'm baffled as hell. ART

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RE: PEP0238 lament
by Bjorn Pettersen July 23, 2001

July 23, 2001

> From: Paul Prescod [mailto:paulp@ActiveState.com] > > This issue is constantly presented as some sort of dichotomy between > "regular" programmers" and newbies. But really it is more of a > dichotomy between those originally trained on typed languages and > those on dynamically typed languages. > > The other languages in the Python category (Perl, Ruby, > JavaScript, ...) > all make a different choice for division and the choice is > uncontroversial. Python is the only one of the languages that has a > constant battle on the issue. Ruby seems to be quite in line with (current) Python: irb(main):001:0> puts 1/2 0 nil irb(main):002:0> puts 1.0/2 0.5 nil irb(main):003:0> -- bjorn

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Re: PEP0238 lament
by Gareth McCaughan July 23, 2001

July 23, 2001

> Here is one that is easier to teach, if you just reverse the order > of teaching calculus and first-order logic and basic set theory. > > A function is continuous at c if, when embedding the world of Reals > into a saturated model (or, say, 2^{Beth_omega} saturated, if you > don't want to get into subtle assumptions), for every infinitesimal x, > f(c+x)-f(c) is an infintesimal. Ahhhh, it's good to see another right-thinking person on c.l.py ... Perhaps if Christian Tismer finds that Stackless is too easy he might be persuaded to maintain Nonstandard Python. :-) -- Gareth McCaughan Gareth.McCaughan(a)pobox.com .sig under construc

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Re: PEP0238 lament
by Guido van Rossum July 22, 2001

July 22, 2001

Arthur Siegel and I seem to be pushing each other's buttons constantly. I don't know why it is, but ever post of his feels like a flame or flamebait to me. I always feel that he attacks me as a person rather than attacking my arguments (usually because he claims that I haven't given any arguments). Try as I may, this makes it very hard, almost impossible for me to respond in a meaningful manner to Arthur's posts. I wonder what I've done to tick him off. I also wonder how come he is so good at ticking me off. The reason for wanting / to return a float (or at least a type that can represent close approximations of numbers like 0.75) has been discussed many times before. The summary of the argument in the PEP may not be complete, but I disagree with Arthur's assessment that integer division is not a problem -- the VPython folks have ample experience that it is. Because all Arthur does is tick me off, I'll leave it at this -- maybe someone else can explain it all to him. --Guido van Rossum (home page: http://www.python.org/~guido/)

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Re: [Edu-sig] fun w/ word list
by Chris Meyers July 22, 2001

July 22, 2001

Hi Brent, Yes, these are fun. In Python for fun, the user input module has some stuff like this. Mainly spell check in Python. If anyone needs a word list file you can download http://www.ibiblio.org/obp/py4fun/spell.tar.gz It's all of about 180Kb compressed. Here's a little challenge for anyone. Do you know the "Jumble" in some newspapers where you have figure out that "ygenxo" is the word "oxygen"? Actually many people miss that one. Write a bit of Python that solves these like single lookup instantaneously! Chris 07/21/2001 2:12:18 PM, "Brent Burley and Pat Erb" <erburley(a)ix.netcom.com> wrote: >One of the things I enjoyed while learning to program was playing with a >spell check library (anyone remember Borland's Turbo Lightning?) and >writing various word filters. This is now trivial in python: > >>>> words = open('/usr/share/dict/words').readlines() >>>> words = [w[:-1] for w in words] # strip newline chars >>>> def aeiou(w): # return true if word uses every vowel >... f = string.find >... for c in 'aeiou': >... if f(w, c) == -1: return 0 >... return 1 >>>> filter(aeiou, words) >['adventitious', 'aeronautic', 'ambidextrous', 'argillaceous', >'argumentation', 'auctioneer', 'audiotape', 'augmentation', >'aureomycin', ...] > >Other ideas: >- find palindromes >- find the words with the most number of each letter >- find words with no vowels >- find the word with the most vowels/consonants in a row >- make a histogram of letters used >- find words whose reverse is a word >- build a crossword puzzle solver > >Most systems have a word list, but perhaps not in the location >shown above. Try 'man spell' and look in the FILES section. > > Brent Burley > > >_______________________________________________ >Edu-sig mailing list >Edu-sig(a)python.org >http://mail.python.org/mailman/listinfo/edu-sig >

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