Re: [Tutor] Newbie Anxiety
Ah, memory lane time again :-) A good natured word of explanation for Chris and others: 10 FORN=1TO10:?N:NEXTN: REM It is bad form not to name N after NEXT to label which FOR NEXT loop is being incremented. Oh, you had advanced BASIC - it allowed nested for loops! :-) My first BASIC only allowed for loops that could be written in a single line...Anything more complex you had to call a subroutine with GOSUB. and replacing big IBM systems with tiny multi-user systems, and we had only 48,000 bytes of RAM CORE, of which 20,500 bytes was used for the entire operating system, Yes, I remember those days, in fact 48K was quite generous! My original box only had 16K RAM and 16K ROM for the OS and interpreter. SPEED, which meant a lightning fast BASIC (which we hired Steve Jobs to Ah yes, now there's another difference. Our BASIC was SLOW! The machine was slow too, it had a 500KHz clock - yes, half a megahertz! accomplished in a single program, thus forcing a jump to a new program, all of which again cut down on speed of getting things done because we had to write our variables to disk before making the jump, You had Disks?!! We were using loops of punched tape... reloaded them in the chained program next to be executed making a big PAUSE in the process of processing. Yes, the forerunner of Overlay programming, I used to have such fun debugging Overlays! :-( line-number-orientated language, and GOTO naturally follows as the size of the program increases. And here we have another advanced feature. Our BASIC didn't renumber GOTO or GOSUB statements, you had to do that manually. Thats why we used a lot of GOSUB but very few GOTO. And SUBs were all given 1000 lines each to minimise risk of renumbering... point of view, that the real grade for excellence that counts, is the real world reward of what happens and continues to happen with your business's bank account. Depends on how you measure excellence. A lot of excellent software has been written by companies that went bust. The software was sufficiently excellent to survive and be bought out or just made publicly available as open source. So excellence can also be measured on how long lived the software is regardless of how long lived be the commercial body that created it. And while I am sure someone is thinking Spaghetti Code, our style was highly conventionalized, something that we enforced rather strictly. Yep you can write structured assembly and spaghetti Python. Its ultimately about behaviours not language. writing 99% of our code in Basic. (IT WAS A VERY VERY VERY FAST BASIC.) So, you see, Basic was my ONLY language. But I've fortunately never been limited to one language, even on my most primitive machines I've had recourse to assembler, and usually some kind of scripting environment. Only on very early PCs, where BASIC was the OS was I so restricted - and PEEK/POKE were my friends :-). only real concern has been in how the flow of python works for the WHOLE PROGRAM FLOW, and you all have help me a lot here...and I really One of the things that some folks find hard is divorcing themselves from that old line by line way of thinking. Modern languages can seem a little like black magic at times(*) - especially when you start programming with objects. The trick is to trust the language and just believe it will work! :-) (*)I'm having the same problem right now with the JSP Tomcat/Struts framework where all sorts of magical things just seem to happen. I keep fighting my desire to go trawl through the source code to see what's going on. Then I tell myself ' just trust in the force Luke...' Enjoy your voyage of discovery and question us freely here on tutor. Alan G Author of the learn to program web tutor http://www.freenetpages.co.uk/hp/alan.gauld ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Newbie Anxiety
On 11/11/05, Terry Kemmerer [EMAIL PROTECTED] wrote: I'm working on Ch. 5, Fruitful Functions, or How To Think Like A Computer Scientist and I still can't count. (Don't laugh! I can't play the violin either...) In Basic, I would have said: 10 x = x + 1 : print x : goto 10 run 1 2 3 etc How is this done in Python? (So I can stop holding my breath as I study this great languageand relax.) Hi Terry, There's a couple of options. First, we could do it with a while loop. This is not the best or the most idiomatic way, but it's probably most similar to what you've seen before. count forever i = 0 while True: print i i = i + 1 Of course, we generally don't want to keep counting forever. Maybe we'll count up to 9. count to 9 i = 0 while i 10:: print i i = i + 1 A while loop contains an implicit GOTO start at the end. At the start, it checks the condition, and breaks out of the loop if the condition is false. Like i said, though, this is not idiomatic Python. Python has for loops which are based around the idea of iterating over a sequence. So, we could count to 9 like this: count to 9 for i in [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]: print i The loop will go through the list, assigning each item to i in turn, until the list is exhausted. The range() function is useful for building lists like that, so we don't have to type it out manually. count to 9 for i in range(10): print i And, of course, once we've got range(), we can give it a variable limit (eg, n = 10; range(n)). Iteration is the key to doing all kinds of funky stuff in python (including new ideas like geneartor functions), so it's good to get the hang of :-) -- John. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Newbie Anxiety
Terry Kemmerer wrote: In Basic, I would have said: 10 x = x + 1 : print x : goto 10 run 1 2 3 etc How is this done in Python? (So I can stop holding my breath as I study this great languageand relax.) In Python there is no goto, as you have discovered. Loops are constructed using the 'for' and 'while' statements. A while loop will loop as long as its condition is true. If you give it a condition that is always true, it will create an infinite loop like yours above. So the equivalent Python code would be x=0 while True: x = x + 1 print x You can read a little more about while loops here and in the next chapter of your book: http://docs.python.org/tut/node5.html#SECTION00520 Now relax and forget all the bad habits from you BASIC days ;-) Kent -- http://www.kentsjohnson.com ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Newbie Anxiety
Terry Kemmerer wrote: I'm working on Ch. 5, Fruitful Functions, or How To Think Like A Computer Scientist and I still can't count. (Don't laugh! I can't play the violin either...) In Basic, I would have said: 10 x = x + 1 : print x : goto 10 run 1 2 3 etc How is this done in Python? (So I can stop holding my breath as I study this great languageand relax.) You need to choose the appropriate control structure. In this case you need an infinite loop, which in Python is written as: while True: # do stuff... Also, in Python you need to explicitly give x its initial value: x = 0 In Python 'x = x + 1' can be written shorter as 'x += 1' (though 'x = x + 1') works too. All together: x = 0 while True: x += 1 print x HTH -- If I have been able to see further, it was only because I stood on the shoulders of giants. -- Isaac Newton Roel Schroeven ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Newbie Anxiety
On Thu, 10 Nov 2005, Terry Kemmerer wrote: I'm working on Ch. 5, Fruitful Functions, or How To Think Like A Computer Scientist and I still can't count. (Don't laugh! I can't play the violin either...) In Basic, I would have said: 10 x = x + 1 : print x : goto 10 Good heavens! I never used GOTO, even on the C-64: 10 for n = 1 to 10 20 print n 25 rem n = 1 rem remove first rem for infinite loop 30 next run 1 2 3 etc I don't know why, but this great UNKNOWN bothers me a lot. Maybe it is because it was the first thing I learned in Basic, back 20 years ago when I was actually a programmer But I think it goes toward visualizing how things are going flow and be constructed without line numbers and the venerable GOTO statement. How is this done in Python? (So I can stop holding my breath as I study this great languageand relax.) n = 1 while n = 10: print n n = n + 1 Or: for n in [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ]: print n Or: for n in range(10): print n + 1 Etc.. -- Chris F.A. Johnson http://cfaj.freeshell.org == Shell Scripting Recipes: A Problem-Solution Approach, 2005, Apress http://www.torfree.net/~chris/books/cfaj/ssr.html ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Newbie Anxiety
In Basic, I would have said: 10 x = x + 1 : print x : goto 10 Tsk, tsk, even in BASIC that's considered bad form :-) 10 FOR X =1 to 10 20 PRINT X 30 NEXT Would be the better BASIC form. And as you've seen Python provides a close analog to that in its for loop. for X in [1,2,3,4,5,6,7,8,9,10]: print X OR for X in range(1,11): print X goes toward visualizing how things are going flow and be constructed without line numbers and the venerable GOTO statement. I discuss why this is a bad idea in the old version of my tutor, which compared Python to old style BASIC. You might find it helpful if you were weaned on BASIC. You can still find the old site here: http://www.freenetpages.co.uk/hp/alan.gauld/oldtutor/ Check out the Loops topic for the GOTO discussion. Alan G Author of the learn to program web tutor http://www.freenetpages.co.uk/hp/alan.gauld ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Newbie Anxiety
compared Python to old style BASIC. You might find it helpful if you were weaned on BASIC. You can still find the old site here: http://www.freenetpages.co.uk/hp/alan.gauld/oldtutor/ Check out the Loops topic for the GOTO discussion. Oops, so long since I looked at that version... Its actually the Branching topic that discusses GOTO. Alan G Author of the learn to program web tutor http://www.freenetpages.co.uk/hp/alan.gauld ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Newbie Anxiety
Title: Message Hi Terry, Python is great, very much so if the last you used was Basic. I highly recommend Alan Gauld's tutorial, but I look forward to your queries here. :-) Liam Clarke-Hutchinson -Original Message-From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Terry KemmererSent: Friday, 11 November 2005 12:25 p.m.To: Python_TUTORSubject: [Tutor] Newbie Anxiety (I accidentally sent this to the originator. Sorry.)Sweet! Almost everything is sooo familiar, yet, merged in many interesting ways. I never had a DO WHILE statement, but in many ways, your further examples are like a combination of my old FOR NEXT loop and IF logical evaluation statement put together for reading in/out lists. JUST TOO COOL! And it looks so CLEAN! --compared to my old BASIC of having to name the variable belonging to each NEXT incrementation executed while keeping the code nested properly relative to each FOR NEXT loop!!!Thanks! THIS LOOKS GREAT!TerryOn Fri, 2005-11-11 at 11:49 +1300, John Fouhy wrote: On 11/11/05, Terry Kemmerer [EMAIL PROTECTED] wrote: I'm working on Ch. 5, "Fruitful Functions", or "How To Think Like A Computer Scientist" and I still can't count. (Don't laugh! I can't play the violin either...) In Basic, I would have said: 10 x = x + 1 : print x : goto 10 run 1 2 3 etc How is this done in Python? (So I can stop holding my breath as I study this great languageand relax.) Hi Terry, There's a couple of options. First, we could do it with a while loop. This is not the best or the most idiomatic way, but it's probably most similar to what you've seen before. count forever i = 0 while True: print i i = i + 1 Of course, we generally don't want to keep counting forever. Maybe we'll count up to 9. count to 9 i = 0 while i 10:: print i i = i + 1 A while loop contains an implicit "GOTO start" at the end. At the start, it checks the condition, and breaks out of the loop if the condition is false. Like i said, though, this is not idiomatic Python. Python has for loops which are based around the idea of iterating over a sequence. So, we could count to 9 like this: count to 9 for i in [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]: print i The loop will go through the list, assigning each item to i in turn, until the list is exhausted. The range() function is useful for building lists like that, so we don't have to type it out manually. count to 9 for i in range(10): print i And, of course, once we've got range(), we can give it a variable limit (eg, n = 10; range(n)). Iteration is the key to doing all kinds of funky stuff in python (including new ideas like geneartor functions), so it's good to get the hang of :-) -- John. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor A new monthly electronic newsletter covering all aspects of MED's work is now available. Subscribers can choose to receive news from any or all of seven categories, free of charge: Growth and Innovation, Strategic Directions, Energy and Resources, Business News, ICT, Consumer Issues and Tourism. See http://news.business.govt.nz for more details. govt.nz- connecting you to New Zealand central local government services Any opinions expressed in this message are not necessarily those of the Ministry of Economic Development. This message and any files transmitted with it are confidential and solely for the use of the intended recipient. If you are not the intended recipient or the person responsible for delivery to the intended recipient, be advised that you have received this message in error and that any use is strictly prohibited. Please contact the sender and delete the message and any attachment from your computer. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
