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  • Help with copy and deepcopy in Python

    - by Az
    Hi there, I think I tried to ask for far too much in my previous question so apologies for that. Let me lay out my situation in as simple a manner as I can this time. Basically, I've got a bunch of dictionaries that reference my objects, which are in turn mapped using SQLAlchemy. All fine with me. However, I want to make iterative changes to the contents of those dictionaries. The problem is that doing so will change the objects they reference---and using copy.copy() does no good since it only copies the references contained within the dictionary. Thus even if copied something, when I try to, say print the contents of the dictionary, I'll only get the latest updated values for the object. This is why I wanted to use copy.deepcopy() but that does not work with SQLAlchemy. Now I'm in a dilemma since I need to copy certain attributes of my object before making said iterative changes. In summary, I need to use SQLAlchemy and at the same time make sure I can have a copy of my object attributes when making changes so I don't change the referenced object itself. Any advice, help, suggestions, etc.?

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  • side effect gotchas in python/numpy? horror stories and narrow escapes wanted

    - by shabbychef
    I am considering moving from Matlab to Python/numpy for data analysis and numerical simulations. I have used Matlab (and SML-NJ) for years, and am very comfortable in the functional environment without side effects (barring I/O), but am a little reluctant about the side effects in Python. Can people share their favorite gotchas regarding side effects, and if possible, how they got around them? As an example, I was a bit surprised when I tried the following code in Python: lofls = [[]] * 4 #an accident waiting to happen! lofls[0].append(7) #not what I was expecting... print lofls #gives [[7], [7], [7], [7]] #instead, I should have done this (I think) lofls = [[] for x in range(4)] lofls[0].append(7) #only appends to the first list print lofls #gives [[7], [], [], []] thanks in advance

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  • Why is my simple recusive method's final return value always off by 1?

    - by FrankTheTank
    I'm attempting to create a text-based version of this game: http://www.cse.nd.edu/java/SameGame.html Here is the code I have so far: #include <iostream> #include <vector> #include <ctime> class Clickomania { public: Clickomania(); std::vector<std::vector<int> > board; int move(int, int); bool isSolved(); void print(); void pushDown(); bool isValid(); }; Clickomania::Clickomania() : board(12, std::vector<int>(8,0)) { srand((unsigned)time(0)); for(int i = 0; i < 12; i++) { for(int j = 0; j < 8; j++) { int color = (rand() % 3) + 1; board[i][j] = color; } } } void Clickomania::pushDown() { for(int i = 0; i < 8; i++) { for(int j = 0; j < 12; j++) { if (board[j][i] == 0) { for(int k = j; k > 0; k--) { board[k][i] = board[k-1][i]; } board[0][i] = 0; } } } } int Clickomania::move(int row, int col) { bool match = false; int totalMatches = 0; if (row > 12 || row < 0 || col > 8 || col < 0) { return 0; } int currentColor = board[row][col]; board[row][col] = 0; if ((row + 1) < 12) { if (board[row+1][col] == currentColor) { match = true; totalMatches++; totalMatches += move(row+1, col); } } if ((row - 1) >= 0) { if (board[row-1][col] == currentColor) { match = true; totalMatches++; totalMatches += move(row-1, col); } } if ((col + 1) < 8) { if (board[row][col+1] == currentColor) { match = true; totalMatches++; totalMatches += move(row, col+1); } } if ((col - 1) >= 0) { if (board[row][col-1] == currentColor) { match = true; totalMatches++; totalMatches += move(row, col-1); } } return totalMatches; } void Clickomania::print() { for(int i = 0; i < 12; i++) { for(int j = 0; j < 8; j++) { std::cout << board[i][j]; } std::cout << "\n"; } } int main() { Clickomania game; game.print(); int row; int col; std::cout << "Enter row: "; std::cin >> row; std::cout << "Enter col: "; std::cin >> col; int numDestroyed = game.move(row,col); game.print(); std::cout << "Destroyed: " << numDestroyed << "\n"; } The method that is giving me trouble is my "move" method. This method, given a pair of coordinates, should delete all the squares at that coordinate with the same number and likewise with all the squares with the same number connected to it. If you play the link I gave above you'll see how the deletion works on a click. int Clickomania::move(int row, int col) { bool match = false; int totalMatches = 0; if (row > 12 || row < 0 || col > 8 || col < 0) { return 0; } int currentColor = board[row][col]; board[row][col] = 0; if ((row + 1) < 12) { if (board[row+1][col] == currentColor) { match = true; totalMatches++; totalMatches += move(row+1, col); } } if ((row - 1) >= 0) { if (board[row-1][col] == currentColor) { match = true; totalMatches++; totalMatches += move(row-1, col); } } if ((col + 1) < 8) { if (board[row][col+1] == currentColor) { match = true; totalMatches++; totalMatches += move(row, col+1); } } if ((col - 1) >= 0) { if (board[row][col-1] == currentColor) { match = true; totalMatches++; totalMatches += move(row, col-1); } } return totalMatches; } My move() method above works fine, as in, it will delete the appropriate "blocks" and replace them with zeros. However, the number of destroyed (value returned) is always one off (too small). I believe this is because the first call of move() isn't being counted but I don't know how to differentiate between the first call or subsequent calls in that recursive method. How can I modify my move() method so it returns the correct number of destroyed blocks?

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  • How to learn flex?

    - by Zenzen
    So I'm starting an internship as a Flex developer in ~2weeks thanks to a friend of mine. The thing is I know squat about Flex - it is an internship after all so I'm supposed to learn there, but nonetheless I want to have some basic understanding of Flex before I start (eventually I want to become a JEE/Flex dev). So my question is simple, which book(s) would you recommend me to start with? Are there any "must have" books, like let's say "Thinking in C++" for C++ etc.? I already heard about a few video tutorials and I will surely check them out but I'd also want to get some decent books.

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  • Strengths and weaknesses of JIT compilers for Python

    - by Az
    Hi there, I'm currently aware of the following Python JIT compilers: Psyco, PyPy and Unladen Swallow. Basically, I'd like to ask for your personal experiences on the strengths and weaknesses of these compilers - and if there are any others worth looking into. Thanks in advance, Az

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  • Does code in the constructor add to code in subclass constructors?

    - by Jeremy Rudd
    Does code in the constructor add to code in subclass constructors? Or does the subclass's constructor override the superclass? Given this example superclass constructor: class Car{ function Car(){ trace("CAR") } } ...and this subclass constructor: class FordCar extends Car{ function FordCar(){ trace("FORD") } } When an instance of FordCar is created, will this trace "Car" and "Ford" ??

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  • Java: how to access assignments in try-catch -loop?

    - by HH
    $ javac TestInit2.java TestInit2.java:13: variable unknown might not have been initialized System.out.println(unknown); ^ 1 error Code import java.util.*; import java.io.*; public class TestInit2 { public static void main(String[] args){ String unknown; try{ unknown="cannot see me, why?"; }catch(Exception e){ e.printStackTrace(); } System.out.println(unknown); } }

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  • Numerating Comments

    - by John
    The code below prints out all comments for a given "submissionid" in chronological order. How could I numerate these comments? (In other words, how do I print out a "1." next to the oldest comment, a "2." next to the second-oldest comment, etc.?) $submission = mysql_real_escape_string($_GET['submission']); $submissionid = mysql_real_escape_string($_GET['submissionid']); $sqlStr = "SELECT comment.comment, comment.datecommented, login.username FROM comment LEFT JOIN login ON comment.loginid=login.loginid WHERE submissionid=$submissionid ORDER BY comment.datecommented ASC LIMIT 100"; $result = mysql_query($sqlStr); $arr = array(); echo "<table class=\"commentecho\">"; while ($row = mysql_fetch_array($result)) { echo '<tr>'; echo '<td class="commentname1">'.stripslashes($row["comment"]).'</td>'; echo '</tr>'; echo '<tr>'; echo '<td class="commentname2"><a href="http://www...com/sandbox/members/index.php?profile='.$row["username"].'">'.$row["username"].'</a>'.date('l, F j, Y &\nb\sp &\nb\sp g:i a &\nb\sp &\nb\sp \N\E\W &\nb\sp \Y\O\R\K &\nb\sp \T\I\M\E', strtotime($row["datecommented"])).'</td>'; echo '</tr>'; } echo "</table>"

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  • Guaranteed COM object release?

    - by Jurily
    I wrote the following code under the assumption that Excel will die with Monkey: class ExcelMonkey { private static Excel.Application xl = new Excel.Application(); public static bool parse(string filename) { if (filename.Contains("foo")) { var workbook = xl.Workbooks.Open(filename); var sheet = workbook.Worksheets.get_Item(1); // do stuff return true; } return false; } } How do I make sure it does? Do I need to release workbook and sheet separately? I want to have Excel around for the lifetime of the program, it's a huge performance improvement.

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  • Strange Bubble sort behaviour.

    - by user271528
    Can anyone explain why this bubble sort function doesn't work and why I loose number in my output. I'm very new to C, so please forgive me if this is something very obvious I have missed. #include <stdio.h> #include int bubble(int array[],int length) { int i, j; int temp; for(i = 0; i < (length); ++i) { for(j = 0; j < (length - 1); ++j) { if(array[i] array[i+1]) { temp = array[i+1]; array[i+1] = array[i]; array[i] = temp; } } } return 0; } int main() { int array[] = {12,234,3452,5643,0}; int i; int length; length = (sizeof(array)/sizeof(int)); printf("Size of array = %d\n", length); bubble(array, length); for (i = 0; i < (length); ++i) { printf("%d\n", array[i]); } return 0; } Output Size of array = 5 12 234 3452 0 0

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  • How to parse XML file to get specific data effectively

    - by Carlos_Liu
    I have an XML file looks like this: <?xml version="1.0" encoding="utf-8" ?> <PathMasks> <Mask desc="Masks_X1"> <config id="01" mask="88" /> <config id="03" mask="80" /> <config id="51" mask="85" /> </Mask> <Mask desc="Masks_X2"> <config id="70" mask="1" /> <config id="73" mask="6" /> </Mask> <Types> <path id="01" desc="TC->PP1" /> <path id="02" desc="TC->PP2" /> <path id="03" desc="TC->PPn" /> </Types> </PathMasks> How to parse the file and get all the data of Mask_X1 as following: id value ===== 01, 88 03, 80 51, 85

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  • How do I create a list or set object in a class in Python?

    - by Az
    For my project, the role of the Lecturer (defined as a class) is to offer projects to students. Project itself is also a class. I have some global dictionaries, keyed by the unique numeric id's for lecturers and projects that map to objects. Thus for the "lecturers" dictionary (currently): lecturer[id] = Lecturer(lec_name, lec_id, max_students) I'm currently reading in a white-space delimited text file that has been generated from a database. I have no direct access to the database so I haven't much say on how the file is formatted. Here's a fictionalised snippet that shows how the text file is structured. Please pardon the cheesiness. 0001 001 "Miyamoto, S." "Even Newer Super Mario Bros" 0002 001 "Miyamoto, S." "Legend of Zelda: Skies of Hyrule" 0003 002 "Molyneux, P." "Project Milo" 0004 002 "Molyneux, P." "Fable III" 0005 003 "Blow, J." "Ponytail" The structure of each line is basically proj_id, lec_id, lec_name, proj_name. Now, I'm currently reading the relevant data into the relevant objects. Thus, proj_id is stored in class Project whereas lec_name is a class Lecturer object, et al. The Lecturer and Project classes are not currently related. However, as I read in each line from the text file, for that line, I wish to read in the project offered by the lecturer into the Lecturer class; I'm already reading the proj_id into the Project class. I'd like to create an object in Lecturer called offered_proj which should be a set or list of the projects offered by that lecturer. Thus whenever, for a line, I read in a new project under the same lec_id, offered_proj will be updated with that project. If I wanted to get display a list of projects offered by a lecturer I'd ideally just want to use print lecturers[lec_id].offered_proj. My Python isn't great and I'd appreciate it if someone could show me a way to do that. I'm not sure if it's better as a set or a list, as well. Update After the advice from Alex Martelli and Oddthinking I went back and made some changes and tried to print the results. Here's the code snippet: for line in csv_file: proj_id = int(line[0]) lec_id = int(line[1]) lec_name = line[2] proj_name = line[3] projects[proj_id] = Project(proj_id, proj_name) lecturers[lec_id] = Lecturer(lec_id, lec_name) if lec_id in lecturers.keys(): lecturers[lec_id].offered_proj.add(proj_id) print lec_id, lecturers[lec_id].offered_proj The print lecturers[lec_id].offered_proj line prints the following output: 001 set([0001]) 001 set([0002]) 002 set([0003]) 002 set([0004]) 003 set([0005]) It basically feels like the set is being over-written or somesuch. So if I try to print for a specific lecturer print lec_id, lecturers[001].offered_proj all I get is the last the proj_id that has been read in.

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  • whats the diference between train, validation and test set, in neural networks?

    - by Daniel
    Im using this library http://pastebin.com/raw.php?i=aMtVv4RZ to implement a learning agent. I have generated the train cases, but i dont know for sure what are the validation and test sets, the teacher says: 70% should be train cases, 10% will be test cases and the rest 20% should be validation cases. Thanks. edit i have this code, for training.. but i have no ideia when to stop training.. def train(self, train, validation, N=0.3, M=0.1): # N: learning rate # M: momentum factor accuracy = list() while(True): error = 0.0 for p in train: input, target = p self.update(input) error = error + self.backPropagate(target, N, M) print "validation" total = 0 for p in validation: input, target = p output = self.update(input) total += sum([abs(target - output) for target, output in zip(target, output)]) #calculates sum of absolute diference between target and output accuracy.append(total) print min(accuracy) print sum(accuracy[-5:])/5 #if i % 100 == 0: print 'error %-14f' % error if ? < ?: break

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  • Change Variable back to original value after Regex matching.

    - by Brad Johansen
    I just "finished" expanding my Palindrome Tester, made in C#. To allow for phrases I added a simple regex match for all non-alphanumeric characters. At the end of the program it states " is(n't) a palindrome." But now with the regex it prints the no spaces/punctuation version of it. I would like to be able to print the original user input. How do I do that? Here is my program: http://gist.github.com/384565

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  • Learning Lisp - Why ?

    - by David
    I really feel that I should learn Lisp and there are plenty of good resources out there to help me do it. I'm not put off by the complicated syntax, but where in "traditional commercial programming" would I find places it would make sense to use it instead of a procedural language. Is there a commercial killer-app out there that's been written in Lisp ?

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  • perl hashes - comparing keys and values

    - by Aaron Moodie
    I've been reading over the perl doc, but I can't quite get my head around hashes. I'm trying to find if a hash key exists, and if so, compare is't value. The thing that is confusing me is that my searches say that you find if a key exists by if (exists $files{$key}) , but that $files{$key} also gives the value? the code i'm working on is: foreach my $item(@new_contents) { next if !-f "$directory/$item"; my $date_modified = (stat("$directory/$item"))[9]; if (exists $files{$item}) { if ($files{$item} != $date_modified { $files{$item} = $date_modified; print "$item has been modified\n"; } } else { $files{$item} = $date_modified; print "$item has been added\n"; } }

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