[Tutor] unicode: % & __str__ & str()
[back to the list after a rather long break] Hello, I stepped on a unicode issue ;-) (one more) Below an illustration: === class U(unicode): def __str__(self): return self # if you can't properly see the string below, # 128 ¶ÿµ ¶ÿµ ¶ÿµ ¶ÿµ ¶ÿµ *** ¶ÿµ *** *** The last line shows that a regular unicode cannot be passed to str() (more or less ok) nor __str__() (not ok at all). Maybe I overlook some obvious point (again). If not, then this means 2 issues in fact: -1- The old ambiguity of str() meaning both "create an instance of type str from the given data" and "build a textual representation of the given object, through __str__", which has always been a semantic flaw for me, becomes concretely problematic when we have text that is not str. Well, i'm very surprised of this. Actually, how comes this point doesn't seem to be very well known; how is it simply possible to use unicode without stepping on this problem? I guess this breaks years or even decades of habits for coders used to write str() when they mean __str__(). -2- How is it possible that __str__ does not work on a unicode object? It seems that the method is simply not implemented on unicode, the type, and __repr__ neither. So that it falls back to str(). Strangely enough, % interpolation works, which means that for both types of text a short circuit is used, namely return the text itself as is. I would have bet my last cents that % would simply delegate to __str__, or maybe that they were the same func in fact, synonyms, but obviously I was wrong! Looking for workarounds, I first tried to overload (or rather create) __str__ like in the U type above. But this solution is far to be ideal cause we still cannot use str() (I mean my digits can write it while my head is who-knows-where). Also, it is really unusable in fact for the following reason: === print c1.__class__ print c1[1].__class__ c3 = c1 ; print (c1+c3).__class__ ==> Any operation will return back a unicode instead of the original type. So that the said type would have to overload all possible operations on text, which is much, indeed, to convert back the results. I don't even speak of performance issues. So, the only solution seems to me to use % everywhere, hunt all str and __str__ and __repr__ and such in all code. I hope I'm wrong on this. Please, give me a better solution ;-) -- la vita e estrany ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] How to manipulate a variable whose value depends on next values of list using LC or reduce()
Shashwat Anand wrote: Shashwat Anand to Bangalore show details 5:31 AM (2 minutes ago) I wrote an LCM function of mine as follows: import fractions def lcm(mylist): # lcm by defination is Lowest Common Multiple # lcm (a*b) = a*b / gcd(a*b) # lcm (a, b, c) = lcm(lcm(a, b), c) # the function lcm() returns lcm of numbers in a list # for the special case of two numbers, pass the argument as lcm([a, b]) sol = 1 for i in mylist: sol = sol * i / fractions.gcd(sol, i) return sol print lcm(range(1, 11)) #gives lcm of numbers (1, 2, 3,9 ,10) print lcm([2, 3]) #gives lcm of two numbers, a special case print lcm([2, 5, 6, 10]) #gives lcm of a random list However I also did a dirty hack as an alternate approach : import fractions l = [1] print max( ( l[i-2], l.append(l[-1] * i / fractions.gcd(l[-1], i ) ) ) for i in range(2, 12) )[0] # prints the LCM of list (1, 10) However to shorten the code i made it totally unpythonic. Can reduce( ) or any other function be of help ? Let me take a test-case as an example: I want to multiple all the content of a given list, now say my list is lst = [2, 3, 9] I can do: sol = 1 for i in lst: sol *= i print sol However this can also be done as: reduce( operator.mul, lst) Can it be done via List Comprehension or we have to do dirty hacks as mentioned above :( Can the LCM function be reduced ? *The point is if we insert a variable( sol here in both test case and LCM case), which changes its values dynamically depending upon the next values of the list, how can I calculate so without going through the long way of using for-construct*, which makes me feel as though i'm coding in C. reduce( ) or even sum( ) does helps in some cases but it constrains me as per my requirement. Any pointers ? Starting where Alan left off, def lcm(mylist): def lcm2(a, b): return a*b / fractions.gcd(a, b) return reduce(lcm2, mylist) or, if you feel the need to get rid of the extra name, def lcm(mylist): return reduce(lambda a,b : a*b/fractions.gcd(a,b), mylist) DaveA ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] How to manipulate a variable whose value depends on next values of list using LC or reduce()
Got it !! @Alan, @DaveA: Hontoni Arigato :) On Fri, Oct 30, 2009 at 9:55 PM, Dave Angel wrote: > Shashwat Anand wrote: > >> Shashwat Anand to Bangalore >> show details 5:31 AM (2 minutes ago) >> >> >> >> I wrote an LCM function of mine as follows: >> >> import fractions >> def lcm(mylist): >># lcm by defination is Lowest Common Multiple >># lcm (a*b) = a*b / gcd(a*b) >># lcm (a, b, c) = lcm(lcm(a, b), c) >># the function lcm() returns lcm of numbers in a list >># for the special case of two numbers, pass the argument as lcm([a, b]) >>sol = 1 >>for i in mylist: >>sol = sol * i / fractions.gcd(sol, i) >>return sol >> >> print lcm(range(1, 11)) #gives lcm of numbers (1, 2, 3,9 ,10) >> print lcm([2, 3]) #gives lcm of two numbers, a special case >> print lcm([2, 5, 6, 10]) #gives lcm of a random list >> >> >> However I also did a dirty hack as an alternate approach : >> >> import fractions >> l = [1] >> print max( ( l[i-2], l.append(l[-1] * i / fractions.gcd(l[-1], i ) ) ) for >> i >> in range(2, 12) )[0] >> # prints the LCM of list (1, 10) >> >> However to shorten the code i made it totally unpythonic. >> Can reduce( ) or any other function be of help ? >> >> Let me take a test-case as an example: >> I want to multiple all the content of a given list, >> now say my list is lst = [2, 3, 9] >> I can do: >> >> sol = 1 >> for i in lst: >>sol *= i >> print sol >> >> However this can also be done as: >> >> >> >>> reduce( operator.mul, lst) > > >> Can it be done via List Comprehension or we have to do dirty hacks as >> mentioned above :( >> Can the LCM function be reduced ? >> >> *The point is if we insert a variable( sol here in both test case and LCM >> case), which changes its values dynamically depending upon the next values >> of the list, how can I calculate so without going through the long way of >> using for-construct*, which makes me feel as though i'm coding in C. >> reduce( >> ) or even sum( ) does helps in some cases but it constrains me as per my >> requirement. Any pointers ? >> >> >> > Starting where Alan left off, > > def lcm(mylist): > def lcm2(a, b): > return a*b / fractions.gcd(a, b) > return reduce(lcm2, mylist) > > or, if you feel the need to get rid of the extra name, > > def lcm(mylist): > return reduce(lambda a,b : a*b/fractions.gcd(a,b), mylist) > > DaveA > ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Sorting points on a 2D plane
The problem belongs to 'Convex Hull' superset. look into : http://en.wikipedia.org/wiki/Convex_hull_algorithms On Thu, Oct 29, 2009 at 6:05 PM, Robert Berman wrote: > > Kent and Alan, > > Thank you both for providing me with tools I can use to develop the sort > portion of my algorithm. They are invaluable. I really appreciate Luke's > willingness to examine and advise on the full algorithm and once it is > written (only the function that determines distance between two points > is written and working) I will definitely add it to pastebin and ask for > your suggestions as well as the suggestions and comments from the group. > > Again, thank you for your help. > > Robert > > ___ > 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] Sorting points on a 2D plane
Hello Shashwat, I have saved the web page for a much more detailed review after I work through the suggestions given by Alan et all. It is obvious that a casual read is not going to be enough. Thank you for the information. Robert On Fri, 2009-10-30 at 23:49 +0530, Shashwat Anand wrote: > The problem belongs to 'Convex Hull' superset. > look into : http://en.wikipedia.org/wiki/Convex_hull_algorithms > > > > On Thu, Oct 29, 2009 at 6:05 PM, Robert Berman > wrote: > > > Kent and Alan, > > Thank you both for providing me with tools I can use to > develop the sort > portion of my algorithm. They are invaluable. I really > appreciate Luke's > willingness to examine and advise on the full algorithm and > once it is > written (only the function that determines distance between > two points > is written and working) I will definitely add it to pastebin > and ask for > your suggestions as well as the suggestions and comments from > the group. > > Again, thank you for your help. > > Robert > > > > ___ > 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] Sorting points on a 2D plane
@Robert: You can look for a similar problem here : https://www.spoj.pl/problems/BSHEEP/ For algorithm I suggest you to go for Graham's scan or Quick hull. On Sat, Oct 31, 2009 at 1:39 AM, Robert Berman wrote: > Hello Shashwat, > > I have saved the web page for a much more detailed review after I work > through the suggestions given by Alan et all. It is obvious that a casual > read is not going to be enough. > > Thank you for the information. > > Robert > > > > On Fri, 2009-10-30 at 23:49 +0530, Shashwat Anand wrote: > > The problem belongs to 'Convex Hull' superset. > look into : http://en.wikipedia.org/wiki/Convex_hull_algorithms > > > On Thu, Oct 29, 2009 at 6:05 PM, Robert Berman > wrote: > > > Kent and Alan, > > Thank you both for providing me with tools I can use to develop the sort > portion of my algorithm. They are invaluable. I really appreciate Luke's > willingness to examine and advise on the full algorithm and once it is > written (only the function that determines distance between two points > is written and working) I will definitely add it to pastebin and ask for > your suggestions as well as the suggestions and comments from the group. > > Again, thank you for your help. > > Robert > > > > ___ > 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
[Tutor] Accessing variables in main from functions in a module
I want to move some functions from my "main" program file to a module file because the main file is getting too big for convenience. The functions access arrays (lists of lists) that are defined and initialised in the main file. How do I reference the main file arrays from statements within the module file? The overall program solves a game by a recursive method. The arrays are the game data. Functions in the main file and also functions in the module need to read and write them. The program works when all the functions are in the main file but now I want to develop it further and the presence of a bunch of unchanging housekeeping functions in the main file makes it cumbersome to read and edit. With everything in the main file a function like the following works as expected: def functionA (row, col, x): grid[row][col] = where grid[] is initialised outside of any functions (i.e. in the main). So how do I write that function when I move it to a module file? I thought I read somewhere that the main routine has the name "__main__" so I tried: __main__.grid[row][col] = <...> but that gives "NameError: name '__main__' is not defined". I understand that it is best to minimize cross-file references but I feel it is warranted in this case. Even if you think it isn't good practice I would like to understand how to do it (or else why it can't be done). Is there some other way to keep files from getting too big? -- Robert Lummis ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Accessing variables in main from functions in a module
"Robert Lummis" wrote I want to move some functions from my "main" program file to a module file because the main file is getting too big for convenience. Good idea! functions access arrays (lists of lists) that are defined and initialised in the main file. How do I reference the main file arrays from statements within the module file? In general you don't. You pass the data into the function. Thats the only (sane) way to make the functions reusable, by passing in all the data they need to do their job. Its also the only sane way to avoid the debugging nightmare of global variables changing under your feet due to hidden function side effects. So when you move the functions, rewrite them from def f(...) # stuff to def f(...grid) #stuff return grid And when you call them do grid = mymod.f(...,grid) That keeps the functions independant and avoids any mysteries about where your main function variables are getting changed. The overall program solves a game by a recursive method. In that case even more reason to pass the data in. Recursive functions opertating on global variables are one of the hardest things to debug in the programming universe, only beaten by multiple threads modifying unsynchronised global variables! and the presence of a bunch of unchanging housekeeping functions in the main file makes it cumbersome to read and edit. Yes thats one reason to move functions out. But an even better reason is to logically partition the code into whats reusable and what is specific to the problem. So consider whether its really the housekeeping that wants moving or the core algorithms... def functionA (row, col, x): grid[row][col] = where grid[] is initialised outside of any functions (i.e. in the main). So how do I write that function when I move it to a module file? I As above def functionA (row, col, x, grid): grid[row][col] = return grid and call it with grid = module.function(row,col,x, grid) thought I read somewhere that the main routine has the name "__main__" A module that is being run directly has the name __main__ not a function. I understand that it is best to minimize cross-file references but I feel it is warranted in this case. I doubt it. Even if you think it isn't good practice I would like to understand how to do it (or else why it can't be done). You can probably do it by inspecting the call stack using the traceback module or somesuch, but there'sd really no need. Is there some other way to keep files from getting too big? You can use classes. You could have a Grid class with all the functions that modify the grid as methods. Then you can create grid objects and operate on them and each will have its own internal grid. You can then easily move the class into a separate module as required. HTH, -- 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] Accessing variables in main from functions in a module
On Fri, Oct 30, 2009 at 6:39 PM, Robert Lummis wrote: > I want to move some functions from my "main" program file to a module > file because the main file is getting too big for convenience. The > functions access arrays (lists of lists) that are defined and > initialised in the main file. How do I reference the main file arrays > from statements within the module file? A couple of solutions: - Put the arrays into some kind of structure that you can pass as an argument. The structure could be a list, dict or custom class. - Create a class (or possibly more than one class) to hold both the data and the functions that operate on it. > With everything in the main file a function like the following works > as expected: > > def functionA (row, col, x): > grid[row][col] = > > where grid[] is initialised outside of any functions (i.e. in the main). > > So how do I write that function when I move it to a module file? I That might make a good method of a grid class. Then it would become something like def functionA(self, row, col, x): self.grid[row][col] = ... > So how do I write that function when I move it to a module file? I > thought I read somewhere that the main routine has the name "__main__" > so I tried: > > __main__.grid[row][col] = <...> > > but that gives "NameError: name '__main__' is not defined". You can import __main__ and the above will work but that is *not* the best solution. > I understand that it is best to minimize cross-file references but I > feel it is warranted in this case. Cross-file references are not bad by themselves but circular references (module A uses module B and B uses A) are a bad idea. > Even if you think it isn't good > practice I would like to understand how to do it (or else why it can't > be done). Is there some other way to keep files from getting too big? Yes. Object-oriented design is the most common way of dealing with this. Think about decomposing your code into cooperating objects. Kent ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] problem adding Tkinter
I apologize in advance for asking such a simple question! I first tried looking through Google, and through the last couple months of this list's archives, and I found some talk about my issue out there but not a detailed enough answer to help someone as new as me. This is my first programming language, so most explanations of this stuff go way over my head! [This is my problem:] I've been using IDLE successfully to do very very simple exercises in Python, and now I wanted to start on some very simple exercises including the Tkinter library. But it looks like it's not set up right and I don't know how to do what I need to do to adjust.. whatever needs to be adjusted. I did the tests listed here: http://wiki.python.org/moin/TkInter I failed at step 2: - Step 2 - can Tkinter be imported? Try the following command at the Python prompt: >>> import Tkinter # no underscore, uppercase 'T' * If it works, go to step 3. * If it fails with "No module named Tkinter", your Python configuration need to be changed to include the directory that contains Tkinter.py in its default module search path. You have probably forgotten to define TKPATH in the Modules/Setup file. A temporary workaround would be to find that directory and add it to your PYTHONPATH environment variable. It is the subdirectory named "lib-tk" of the Python library directory (when using Python 1.4 or before, it is named "tkinter"). -- I could do import _tkinter but not import Tkinter This is what I received back from the Shell: >>> import _tkinter >>> import Tkinter Traceback (most recent call last): File "", line 1, in import Tkinter ImportError: No module named Tkinter >>> Unfortunately, the instructions they gave on what to do if Step 2 fails read like Greek to me. I don't know what a PYTHONPATH is, I don't remember doing anything with a Modules/Setup file, and I don't know what an environment variable is, or what to do with subdirectories. I am running Windows XP. Installed Python 3.1, and IDLE seems to be working okay... When I go to C:\Python31 I see these folders: DLLs Doc include Lib libs tcl Tools There are 3 .exe files: python.exe pythonw.exe w9xpopen.exe I see something called _tkinter.lib in the folder C:\Python31\libs There is a folder called tkinter inside the folder Lib (C:\Python31\Lib\tkinter) Would someone be able to spell out to me in every detailed steps exactly what I should do, assuming I know pretty much nothing about programming or installing a programming language, so that when I put import Tkinter it doesn't error? Thank you very much for reading! -Kristin ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] problem adding Tkinter
SORRY TO ALL: PLEASE DISREGARD MY LAST EMAIL. I kept searching through the Tutor archives and found an answer in the Feb archives. (In Python 3 you have to type tkinter in all lower case.) Thanks all, Kristin On Fri, Oct 30, 2009 at 5:21 PM, Kristin Wilcox wrote: > I apologize in advance for asking such a simple question! I first > tried looking through Google, and through the last couple months of > this list's archives, and I found some talk about my issue out there > but not a detailed enough answer to help someone as new as me. > > This is my first programming language, so most explanations of this > stuff go way over my head! > > [This is my problem:] I've been using IDLE successfully to do very > very simple exercises in Python, and now I wanted to start on some > very simple exercises including the Tkinter library. But it looks like > it's not set up right and I don't know how to do what I need to do to > adjust.. whatever needs to be adjusted. > > I did the tests listed here: http://wiki.python.org/moin/TkInter > > I failed at step 2: > - > Step 2 - can Tkinter be imported? > > Try the following command at the Python prompt: > import Tkinter # no underscore, uppercase 'T' > > * If it works, go to step 3. > * If it fails with "No module named Tkinter", your Python > configuration need to be changed to include the directory that > contains Tkinter.py in its default module search path. You have > probably forgotten to define TKPATH in the Modules/Setup file. A > temporary workaround would be to find that directory and add it to > your PYTHONPATH environment variable. It is the subdirectory named > "lib-tk" of the Python library directory (when using Python 1.4 or > before, it is named "tkinter"). > -- > I could do import _tkinter but not import Tkinter > > This is what I received back from the Shell: import _tkinter import Tkinter > Traceback (most recent call last): > File "", line 1, in > import Tkinter > ImportError: No module named Tkinter > > > Unfortunately, the instructions they gave on what to do if Step 2 > fails read like Greek to me. I don't know what a PYTHONPATH is, I > don't remember doing anything with a Modules/Setup file, and I don't > know what an environment variable is, or what to do with > subdirectories. > > I am running Windows XP. Installed Python 3.1, and IDLE seems to be > working okay... > > When I go to C:\Python31 I see these folders: > DLLs > Doc > include > Lib > libs > tcl > Tools > > There are 3 .exe files: > python.exe > pythonw.exe > w9xpopen.exe > > I see something called _tkinter.lib in the folder C:\Python31\libs > There is a folder called tkinter inside the folder Lib > (C:\Python31\Lib\tkinter) > > Would someone be able to spell out to me in every detailed steps > exactly what I should do, assuming I know pretty much nothing about > programming or installing a programming language, so that when I put > import Tkinter it doesn't error? > > Thank you very much for reading! > > -Kristin > ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] unicode: % & __str__ & str()
spir wrote: [back to the list after a rather long break] Hello, I stepped on a unicode issue ;-) (one more) Below an illustration: class U(unicode): def __str__(self): return self # if you can't properly see the string below, # 128 == Any operation will return back a unicode instead of the original type. So that the said type would have to overload all possible operations on text, which is much, indeed, to convert back the results. I don't even speak of performance issues. So, the only solution seems to me to use % everywhere, hunt all str and __str__ and __repr__ and such in all code. I hope I'm wrong on this. Please, give me a better solution ;-) -- la vita e estrany I'm not the one to help with this, because my unicode experience is rather limited. But I think I know enough to ask a few useful questions. 1) What version of Python are you doing this on, what OS, and what code page is your stdout using? 2) What coding declaration do you have in your source file? Without it, I can't even define those literals. I added the line #-*- coding: utf-8 -*- as line 2 of my source file to get past that one. But I really don't know much about this literal string that I pasted from your email. 3) Could you give us the hex equivalent of the 3 character string you're trying to give us in the email. The only clue you gave us was that the bytes were between 129 and 254, which they aren't, on my machine, at least with a utf-8 coding declaration. repr(u"¶ÿµ") --> u'\xb6\xff\xb5' length= 3 repr(c0) --> '\xc2\xb6\xc3\xbf\xc2\xb5' length = 6 You say that __str__() isn't defined on Unicode objects, but that's not the case, at least in 2.6.2. Works fine on ASCII characters, but something causes an exception for your strings. Since you're eating the exception, all you know is something went wrong, not what went wrong. And since my environment is probably totally different, ... I get the exception text: 'ascii' codec can't encode characters in position 0-2: ordinal not in range(128) Incidentally, you'll probably save yourself a lot of grief in the long run if you change your editor to always expand tabs to spaces (4-per). It's dangerous, and not recommended to mix tabs and spaces in the same file, and it's surprising how often spaces get mixed in by accident. In Python3.x it's illegal to mix them. DaveA ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] problem adding Tkinter
Kristin Wilcox wrote: I apologize in advance for asking such a simple question! I first tried looking through Google, and through the last couple months of this list's archives, and I found some talk about my issue out there but not a detailed enough answer to help someone as new as me. This is my first programming language, so most explanations of this stuff go way over my head! [This is my problem:] I've been using IDLE successfully to do very very simple exercises in Python, and now I wanted to start on some very simple exercises including the Tkinter library. But it looks like it's not set up right and I don't know how to do what I need to do to adjust.. whatever needs to be adjusted. I did the tests listed here: http://wiki.python.org/moin/TkInter I failed at step 2: - Step 2 - can Tkinter be imported? Try the following command at the Python prompt: import Tkinter # no underscore, uppercase 'T' * If it works, go to step 3. * If it fails with "No module named Tkinter", your Python configuration need to be changed to include the directory that contains Tkinter.py in its default module search path. You have probably forgotten to define TKPATH in the Modules/Setup file. A temporary workaround would be to find that directory and add it to your PYTHONPATH environment variable. It is the subdirectory named "lib-tk" of the Python library directory (when using Python 1.4 or before, it is named "tkinter"). -- I could do import _tkinter but not import Tkinter This is what I received back from the Shell: import _tkinter import Tkinter Traceback (most recent call last): File "", line 1, in import Tkinter ImportError: No module named Tkinter Unfortunately, the instructions they gave on what to do if Step 2 fails read like Greek to me. I don't know what a PYTHONPATH is, I don't remember doing anything with a Modules/Setup file, and I don't know what an environment variable is, or what to do with subdirectories. I am running Windows XP. Installed Python 3.1, and IDLE seems to be working okay... When I go to C:\Python31 I see these folders: DLLs Doc include Lib libs tcl Tools There are 3 .exe files: python.exe pythonw.exe w9xpopen.exe I see something called _tkinter.lib in the folder C:\Python31\libs There is a folder called tkinter inside the folder Lib (C:\Python31\Lib\tkinter) Would someone be able to spell out to me in every detailed steps exactly what I should do, assuming I know pretty much nothing about programming or installing a programming language, so that when I put import Tkinter it doesn't error? Thank you very much for reading! -Kristin You're looking at websites describing Python 2.x, but you're using 3.1. The Tkinter module was renamed tkinter. So change import Tkinter to import tkinter and see if it starts working better DaveA ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Accessing variables in main from functions in a module
Kent Johnson wrote: On Fri, Oct 30, 2009 at 6:39 PM, Robert Lummis wrote: I want to move some functions from my "main" program file to a module file because the main file is getting too big for convenience. The functions access arrays (lists of lists) that are defined and initialised in the main file. How do I reference the main file arrays from statements within the module file? A couple of solutions: - Put the arrays into some kind of structure that you can pass as an argument. The structure could be a list, dict or custom class. - Create a class (or possibly more than one class) to hold both the data and the functions that operate on it. With everything in the main file a function like the following works as expected: def functionA (row, col, x): grid[row][col] =a value that depends on x and other values in grid> where grid[] is initialised outside of any functions (i.e. in the main). So how do I write that function when I move it to a module file? I That might make a good method of a grid class. Then it would become something like def functionA(self, row, col, x): self.grid[row][col] =.. So how do I write that function when I move it to a module file? I thought I read somewhere that the main routine has the name "__main__" so I tried: __main__.grid[row][col] =...> but that gives "NameError: name '__main__' is not defined". You can import __main__ and the above will work but that is *not* the best solution. I understand that it is best to minimize cross-file references but I feel it is warranted in this case. Cross-file references are not bad by themselves but circular references (module A uses module B and B uses A) are a bad idea. Even if you think it isn't good practice I would like to understand how to do it (or else why it can't be done). Is there some other way to keep files from getting too big? Yes. Object-oriented design is the most common way of dealing with this. Think about decomposing your code into cooperating objects. Kent Listen to everything Kent tells you. He knows more about Python than I probably ever will. But I have been programming for a long time, and sometimes I have to be pragmatic on the way to becoming correct. So take this next suggestion as a stop-gap while you debug some of these concepts. Make a brand new module just to hold these global variables. Call it constants.py In that module, give your initial values for all these globals, but don't do anything else. If absolutely necessary, make a single function in the module that'll be called at the very beginning of the script to do further initialization. Above all, don't put any imports in this module, except for the obvious stdlib ones, such as os and sys. But not to any other module of your own code. Now, add an import of that module everywhere you need access to these, including from your script. So if you need access to the constant grid, you reference it withconstants.grid Now I deliberately called the module constants because good practice says you'd only use this approach for things which do not change while the program is running. Things like flags passed in from the command line, or environmental things like the directory in which files are to be stored. So if you followed my advice to call it constants.py, then you'd be reminded each time that this is a temporary hack. Personally, I like the class approach, where related data is grouped together, so a single parameter can be added to each function. And many times, this can lead to generalizations where you suddenly realize that instead of one grid, you need to operate on more than one, and the same functions could deal with either one. Passing grid (or a class object containing grid) would then be a fortunate choice. And realize that object-orientation isn't an all-or-nothing approach. Make objects out of those groups of things that you think there's ever going to be a chance of multiple usage, and leave the rest separate values. And in addition to instance attributes, you can create methods, but you could start by doing just the lowest level ones. For example if your grid is implemented as a list of lists, maybe you want accessor methods that give it a different appearance, like a single vector. Or if there are two attributes that are interrelated, you can use methods to keep them in synch, instead of counting on everyone following the rules. DaveA ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] python zlib problem
Hi , For some weird reason or a huge screw up I did my python zlib library has been removed . This is part of standard lib(i think!!!) and it is used by setuptools and many other libraries .What is the safe way in which I can recover this library on ubuntu. My previous try somehow lead to removal of ubuntu-desktop... If this is not the list I should be asking this I am sorry -- A-M-I-T S|S ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] class attribute to initiate more classes
I have a program that generates many instances of a class with an attribute self.x = random.gauss(10, 2). So each instance has a different value for self.x. This is what I want. Now I want to make a class that starts my program and sets the attributes. class people: def __init__(self, size) self.size = size class makepeople: def __init__(self, randomsize) self.rsize = randomsize self.allpeople = [] def makethem(): for x in range(1,100): p+str(x) = people(self.rsize) allpeople.append(p+str(x)) so what I would like to have work is set the attribute of makepeople so that when it is used to make instances of people each will have a different size. listofp = makepeople(random.guass(100, 2)) listofp.makethem() I would then what listofp.allpeople to be a list of people with different sizes. The above code does not work, I don't think it does anyway. I hope this makes sense, I am sure there is a term for what I am trying to do but I don't know it. Thanks Vincent Davis ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] class attribute to initiate more classes
On 31 Oct 2009, at 06:01 , Vincent Davis wrote: I hope this makes sense, I am sure there is a term for what I am trying to do but I don't know it. What a strange program. But at least it compiles: import random class people: def __init__(self, size): self.size = size class makepeople: def __init__(self, randomsize): self.rsize = randomsize self.allpeople = [] def makethem(self): for x in range(self.rsize): self.allpeople.append(people(self.rsize)) listofp = makepeople(int(random.gauss(100, 2))) listofp.makethem() ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Accessing variables in main from functions in a module
Le Fri, 30 Oct 2009 18:39:42 -0400, Robert Lummis s'exprima ainsi: > I want to move some functions from my "main" program file to a module > file because the main file is getting too big for convenience. The > functions access arrays (lists of lists) that are defined and > initialised in the main file. How do I reference the main file arrays > from statements within the module file? It seems to me you're inverting the logic of your program. Actually, the grid represents the game state (right?) and is /input/ for the game logic. So what is to be exported, if you like, is the grid. So, you would have for instance a "game_state.py" module defining eg a "grid" object imported into main program. While maybe the funcs you call "housekeeping" actually hold core logic of the system. If not, it they are really utilities, then have a "housekeeping.py" module that also imports the grid, and itself imported by the main program. But I guess this would not be the simplest solution. Better make your funcs real funcs (in a sense close to math funcs) by feeding them with all their input as parameters and letting them return their result, as Alan suggests (I'm fan of this point of view, too). Instead of having them wildly read and/or write things here and there. Or make your game state an object that holds its own modifying methods as suggested by Kent. Take the opportunity to learn this way of designing an application if you don't know it (well). It would certainly be great in your case; even more if the game is logically structured enough for you to easily split its global state into consistent smaller objects (representing "elements" of the game). Denis -- la vita e estrany ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
