Re: [Tutor] Feedback on coding style
Hi, Re: coding style, I can *really* recommend the book 'Code Complete' (http://cc2e.com/). It doesn't focus on Python specifically, but it's a wonderful book. You can find a pdf checklist of the book if you Google a bit. Cheers!! Albert-Jan ~~ All right, but apart from the sanitation, the medicine, education, wine, public order, irrigation, roads, a fresh water system, and public health, what have the Romans ever done for us? ~~ From: Dave Angel da...@ieee.org To: howit...@archlinux.us Cc: tutor@python.org Sent: Wed, December 8, 2010 11:01:05 PM Subject: Re: [Tutor] Feedback on coding style On 01/-10/-28163 02:59 PM, howit...@archlinux.us wrote: Hi. For the past week, I've been following an online Python guide named: 'Learn Python the Hard Way'. I'm very happy with it as it gives a lot of freedom to explore. However, due to this I have no idea if I'm thinking the right way. That's why I've attached a script of mine I've been working on all day. It works a 100%, but I'm afraid I've made very bad choices concerning design and coding style. (If it could've been much simpler, if there are glaring mistakes, poor methods, ..) Could anyone be so friendly as to offer a bit of feedback, to a newbie? PS: The script very simple accepts 2 arguments from the commandline. First arg being the number to which should be counted, second arg being the interval. Thank you, Adrian I agree with Hugo, probably on all his points. But to help you fix it, I think I can help you a bit as well. First is I think you're misunderstanding the purpose of a function. A function should be a self-contained piece of code that gets called, and that returns when done. You're using them mostly as a way to implement what BASIC used to have as a GOTO. For example, when a loop is needed, you do it by calling another function which calls the first one. That is called recursion if it's done on purpose, and a bug if it happens by accident. Second is that you're misusing global variables. A function needs to be called with those values it needs to do its work, and it needs to return the results of that work. Very seldom should those things be globals. Start with the first function. You declare it with maxn and incr as parameters, and you call it correctly. But it also uses the globals, rather than using the ones passed in. Then the function ask_change(). You should be passing it the two arguments, and getting back modified arguments as return values. And the function shouldn't call the_loop() itself, it should just get the new values. jibjab_result() is trying to be a loop, by effectively calling itself, through choice_result(). If you need a loop, just write one. And that loop will probably be in ask_change(), without needing any other functions inside. It's good to decompose a problem into functions, but you're not using functions in the way they're designed. For small problems, this can work, but as the problems get more complex, you'll be forced to change your habits. DaveA ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Feedback on coding style
Albert-Jan Roskam fo...@yahoo.com wrote Re: coding style, I can *really* recommend the book 'Code Complete' (http://cc2e.com/). It doesn't focus on Python specifically, but it's a wonderful book. I'll second that. I haven't read the 2nd Ed but the first edition was one of the few (5 or 6?) books I've read about computing that actually changed the way I write code. It's not an absolute beginners book, you need a bit of experience in writing reasonable length programs - more than 100 lines say, to really appreciate why some things are recommended, but for the right audience it is, as Albert says, a wonderful book.. -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Feedback on coding style
Thanks a lot for the very friendly and constructive comments. I can't wait to start overhauling the script with the comments received here. If I could repay the friendliness to anyone, let me know. Adrian ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] Feedback on coding style
Hi. For the past week, I've been following an online Python guide named: 'Learn Python the Hard Way'. I'm very happy with it as it gives a lot of freedom to explore. However, due to this I have no idea if I'm thinking the right way. That's why I've attached a script of mine I've been working on all day. It works a 100%, but I'm afraid I've made very bad choices concerning design and coding style. (If it could've been much simpler, if there are glaring mistakes, poor methods, ..) Could anyone be so friendly as to offer a bit of feedback, to a newbie? PS: The script very simple accepts 2 arguments from the commandline. First arg being the number to which should be counted, second arg being the interval. Thank you, Adrian #!/usr/bin/env python # Made with python2.7 from sys import argv from sys import exit script, maxnumber, increment = argv maxnumber = int(maxnumber) increment = int(increment) jibjab = 0 numbers = [] askchange = 1 # The script goes as following: # When you start it and give two arguments, check_OP_size # checks wether you won't get too much output. # If you PASS the test, you're immediately sent to the main # function (the_loop, which is performing the actualy goal # of the script). If you FAIL you're sent to ask_change. # ask_change() notifies you that you're going to get # a lot of output and optionally lets you change your arguments. # You're then sent to choice_result which check if your response # is a valid response (e.g. Y/N). If it's not, you're sent to # jibjab_result that gives you 3 chances to type in Y/N. # If you fail typing Y/N three times, the app quits. # If you make it however, you're sent to: change_vars. # Of course, change_vars also immediately sends you to check_OP_size # to check for OP size. # ANY COMMENTS WELCOME AT howit...@archlinux.us def check_OP_size(maxn, incr): global choice, maxnumber, increment if maxn / incr 10: ask_change() if maxn / incr = 10: the_loop(maxnumber, increment) def ask_change(): global choice, maxnumber, increment print You will recieve a lot of output.\nDo you wish to change your data? choice = raw_input(Y/N: ) choice_result() def jibjab_result(): global choice, jibjab if jibjab 2: jibjab += 1 choice = raw_input(Y/N: ) choice_result() elif jibjab = 2: print Idiot. exit() def choice_result(): global choice, maxnumber, increment if choice == Y: change_vars() elif choice == N: the_loop(maxnumber, increment) else: jibjab_result() def change_vars(): global maxnumber, increment maxnumber = raw_input(Give a new max number: ) increment = raw_input(Give a new increment: ) maxnumber = int(maxnumber) increment = int(increment) check_OP_size(maxnumber, increment) #the_loop(maxnumber, increment) def the_loop(maxn, incr): Advances a number with the supplied increment untill it has reached the passed maximum number. maxn = int(maxn) incr = int(incr) i = 0 #for i in range( 0, maxn, incr): while i maxn: print At the top i is %d % i numbers.append(i) i = i + incr print Numbers now: , numbers print At the bottom i is %d % i check_OP_size(maxnumber, increment) print The numbers: for num in numbers: print num, ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Feedback on coding style
On Wed, Dec 8, 2010 at 8:11 PM, howit...@archlinux.us wrote: Hi. For the past week, I've been following an online Python guide named: 'Learn Python the Hard Way'. I'm very happy with it as it gives a lot of freedom to explore. However, due to this I have no idea if I'm thinking the right way. That's why I've attached a script of mine I've been working on all day. It works a 100%, but I'm afraid I've made very bad choices concerning design and coding style. (If it could've been much simpler, if there are glaring mistakes, poor methods, ..) Could anyone be so friendly as to offer a bit of feedback, to a newbie? I like that you've divided the program up into functions, this is A Good Thing(TM). It made it much easier for me to understand what is going on, so keep doing that. little nitpick (maybe not *so* little), your functions are mutually recursive. This is a difficult word that basically means that they are all calling each other in a cycle that is potentially endless. In this case, the cycle goes like this: check_OP_size - ask_change - choice_result - change_vars - check_OP_size. You see that if I keep inputting the right things, I can go through this cycle endlessly. In this case, it's not a big problem, because no one is likely to do that for long enough to cause problems, but if another part of your program is doing the inputting, it can go wrong quickly. Why? Because functions can't call each other indefinitely. Try running this example: def f(): f() f() This is a function that keeps calling itself, the simplest possible cycle. It gives you an error maximum recursion depth exceeded. There are reasons for this, and you should learn about recursion and the call stack at some point, but that is another long essay. For now it is enough to know that recursion is something to be careful with, as there is a limit to how many functions can call each other. Second, you're using globals too much. Functions should rely as much as possible on their arguments, and nothing else. I can count the number of times I needed the global statement on one hand, and I've programmed a lot of python. Globals make your program difficult to follow, because you can't clearly see where the data is coming from and going to. Rather than having your functions communicate through global variables, you should have them communicate through function arguments and return values. See if you can write a version without the global statements. There are a few other little things. The two if statements in check_OP_size can be rewritten into an if/else statement, since the two checks are complementary (one of them will always be true). The while loop in the_loop is a little overcomplicated (you had the right idea with the commented out range call). Lastly, the program could've been written a lot more succinctly, but this will come with time and practice. Writing code is hard, and getting a feel for how to divide up your functions and how to express yourself in python most naturally will take time and practice. I'd say you're on the right track, and if you get rid of all the globals you'll be well on your way to becoming an excelling python programmer. If you need any more help, let us know. Hugo ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Feedback on coding style
On 01/-10/-28163 02:59 PM, howit...@archlinux.us wrote: Hi. For the past week, I've been following an online Python guide named: 'Learn Python the Hard Way'. I'm very happy with it as it gives a lot of freedom to explore. However, due to this I have no idea if I'm thinking the right way. That's why I've attached a script of mine I've been working on all day. It works a 100%, but I'm afraid I've made very bad choices concerning design and coding style. (If it could've been much simpler, if there are glaring mistakes, poor methods, ..) Could anyone be so friendly as to offer a bit of feedback, to a newbie? PS: The script very simple accepts 2 arguments from the commandline. First arg being the number to which should be counted, second arg being the interval. Thank you, Adrian I agree with Hugo, probably on all his points. But to help you fix it, I think I can help you a bit as well. First is I think you're misunderstanding the purpose of a function. A function should be a self-contained piece of code that gets called, and that returns when done. You're using them mostly as a way to implement what BASIC used to have as a GOTO. For example, when a loop is needed, you do it by calling another function which calls the first one. That is called recursion if it's done on purpose, and a bug if it happens by accident. Second is that you're misusing global variables. A function needs to be called with those values it needs to do its work, and it needs to return the results of that work. Very seldom should those things be globals. Start with the first function. You declare it with maxn and incr as parameters, and you call it correctly. But it also uses the globals, rather than using the ones passed in. Then the function ask_change(). You should be passing it the two arguments, and getting back modified arguments as return values. And the function shouldn't call the_loop() itself, it should just get the new values. jibjab_result() is trying to be a loop, by effectively calling itself, through choice_result(). If you need a loop, just write one. And that loop will probably be in ask_change(), without needing any other functions inside. It's good to decompose a problem into functions, but you're not using functions in the way they're designed. For small problems, this can work, but as the problems get more complex, you'll be forced to change your habits. DaveA ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
