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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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  • 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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  • 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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  • Basic Array Iteration in Ruby

    - by michaelmichael
    What's a better way to traverse an array while iterating through another array? For example, if I have two arrays like the following: names = [ "Rover", "Fido", "Lassie", "Calypso"] breeds = [ "Terrier", "Lhasa Apso", "Collie", "Bulldog"] Assuming the arrays correspond with one another - that is, Rover is a Terrier, Fido is a Lhasa Apso, etc. - I'd like to create a dog class, and a new dog object for each item: class Dog attr_reader :name, :breed def initialize(name, breed) @name = name @breed = breed end end I can iterate through names and breeds with the following: index = 0 names.each do |name| dog = Dog.new("#{name}", "#{breeds[index]}") index = index.next end However, I get the feeling that using the index variable is the wrong way to go about it. What would be a better way?

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  • error C2440: '=' : cannot convert from 'std::string []' to 'std::string []'

    - by Bach
    now what is wrong with this code! Header: #pragma once #include <string> using namespace std; class Menu { public: Menu(string []); ~Menu(void); }; Implementation: #include "Menu.h" string _choices[]; Menu::Menu(string items[]) { _choices = items; } Menu::~Menu(void) { } compiler is complaining: error C2440: '=' : cannot convert from 'std::string []' to 'std::string []' There are no conversions to array types, although there are conversions to references or pointers to arrays there is no conversion! so what is it on about? please help, just need to pass a bloody array of strings and set it to Menu class _choices[] attribute. thanks

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  • Problem running a Python program, error: Name 's' is not defined.

    - by Sergio Tapia
    Here's my code: #This is a game to guess a random number. import random guessTaken = 0 print("Hello! What's your name kid") myName = input() number = random.randint(1,20) print("Well, " + myName + ", I'm thinking of a number between 1 and 20.") while guessTaken < 6: print("Take a guess.") guess = input() guess = int(guess) guessTaken = guessTaken + 1 if guess < number: print("You guessed a little bit too low.") if guess > number: print("You guessed a little too high.") if guess == number: break if guess == number: guessTaken = str(guessTaken) print("Well done " + myName + "! You guessed the number in " + guessTaken + " guesses!") if guess != number: number = str(number) print("No dice kid. I was thinking of this number: " + number) This is the error I get: Name error: Name 's' is not defined. I think the problem may be that I have Python 3 installed, but the program is being interpreted by Python 2.6. I'm using Linux Mint if that can help you guys help me. Using Geany as the IDE and pressing F5 to test it. It may be loading 2.6 by default, but I don't really know. :( Edit: Error 1 is: File "GuessingGame.py", line 8, in <Module> myName = input() Error 2 is: File <string>, line 1, in <Module>

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  • How to get the original variable name of variable passed to a function

    - by Acorn
    Is it possible to get the original variable name of a variable passed to a function? E.g. foobar = "foo" def func(var): print var.origname So that: func(foobar) Returns: >>foobar EDIT: All I was trying to do was make a function like: def log(soup): f = open(varname+'.html', 'w') print >>f, soup.prettify() f.close() .. and have the function generate the filename from the name of the variable passed to it. I suppose if it's not possible I'll just have to pass the variable and the variable's name as a string each time.

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  • How do I make lines scale when using GLOrtho?

    - by Mason Wheeler
    I'm using GLOrtho to set up a 2D view that I can render textures onto. It works really well, up until I try to zoom in on the image. If I pass half the width and half the height of the viewport to GLOrtho, I end up with all my textures displayed twice as big as normal, which is exactly what I expect. But then I try to draw a box around part of the image and it all falls apart. I call glBegin(GL_LINE_LOOP), place the four vertices, and call glEnd, and I expect to see the same thing I would see if I drew it at normal zoom level, doubled. Instead, I get lines that are all the right length, but they all come out one pixel wide, instead of two, and it looks really bad. What am I missing?

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  • Why do I not get the correct answer for Euler 56 in J?

    - by Gregory Higley
    I've solved 84 of the Project Euler problems, mostly in Haskell. I am now going back and trying to solve in J some of those I already solved in Haskell, as an exercise in learning J. Currently, I am trying to solve Problem 56. Let me stress that I already know what the right answer is, since I've already solved it in Haskell. It's a very easy, trivial problem. I will not give the answer here. Here is my solution in J: digits =: ("."0)":"0 eachDigit =: adverb : 'u@:digits"0' NB. I use this so often I made it an adverb. cartesian =: adverb : '((#~ #) u ($~ ([:*~#)))' >./ +/ eachDigit x: ^ cartesian : i. 99 This produces a number less than the desired result. In other words, it's wrong somehow. Any J-ers out there know why? I'm baffled, since it's pretty straightforward and totally brute force.

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  • Do I correctly understand what a class is?

    - by Matt
    I've had trouble finding a clear, concise laymans definition of a class. Usually, they give general ideas without specifically spelling it out, and I'm wondering if I'm understanding this correctly. As I understand it, a class is the set of code that controls an object. For example, in an app that has a button for 'Yes' and a button for 'No', and a text box for output, the code that tells the computer what to do when the user uses the Yes button is one class, the code for hitting No is another class, and an object is the two buttons and what they do together to influence the output box. Am I right, or am I confusing terms here? Thanks

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  • Inserting multiple types into an SQLite database with Python

    - by mankoff
    I'm trying to create an SQLite 3 database from Python. I have a few types I'd like to insert into each record: A float, and then 3 groups of n floats, currently a tuple but could be an array or list.. I'm not well-enough versed in Python to understand all the differences. My problem is the INSERT statement. DAS = 12345 lats = (42,43,44,45) lons = (10,11,12,13) times = (1,2,3,4,5,6,7,8,9) import sqlite3 connection = sqlite3.connect("test.db") cursor = connection.cursor() cursor.execute( "create table foo(DAS LONG PRIMARY KEY,lats real(4),lons real(4), times real(9) )" ) I'm not sure what comes next. Something along the lines of: cmd = 'INSERT into foo values (?,?,?,?), ..." cursor.execute(cmd) How should I best build the SQL insert command given this data?

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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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  • View Animation (Resizing a Ball)

    - by user270811
    hi, i am trying to do this: 1) user long touches the screen, 2) a circle/ball pops up (centered around the user's finger) and grows in size as long as the user is touching the screen 3) once the user lets go of the finger, the ball (now in its final size) will bounce around. i think i have the bouncing around figure out from the DivideAndConquer example, but i am not sure how to animate the ball's growth. i looked at various view flipper examples such as this: http://www.inter-fuser.com/2009/08/android-animations-3d-flip.html but it seems like view flipper is best for swapping two static pictures. i wasn't able to find a good view animator example other than the flippers. also, i would prefer to use images as opposed to just a circle. can someone point me in the right direction? thanks.

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  • vb.net getsettings

    - by PandaNL
    Hello, I need a form width a checkbox "Don't show this again" for my winform, but how can i make this so when my Form1 loads it checks the state of the checkbox using the getsettings option? How can is save the checkbox state to the registery? and how do i get the state? If Form2.Checkbox.checked = Getsettings() Then Form2.showdialog Else Goto Skip End IF Skip:

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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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  • So do programming languages get updated regularly like everyday applications or are they just x.0 re

    - by Randy
    I was wondering if programming languages and frameworks get updated in small increments or are they just x.0 releases? And if they do how do you keep up on all the changes in every update? I am specifically interested in Objective-C and Cocoa and CocoaTouch. I'm learning from books and online PDF's etc, but often they are at best a few years old. I just would like to know if there have been any changes etc. that should concern me and even if not, inevitably there will be, so where can I look out for them?

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  • Need to add underscore to my regex

    - by TaMeR
    I suck at regular expression and just can't seem to figure this out. '/^[A-Za-z0-9](?:.[A-Za-z0-9]+)*$/' As it's right now it allows dots anytime after the first char and I like to add _ so that it allows both. Thanks

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  • PHP OOP properity constant usage

    - by Misiur
    Hi there. I'm really new to OOP. I'm even not a newbie - I'm noob. So. I want to transfer my pseudo-CMS from "normal" programming, into OOP programming system. And so: private static $dsn = DB_TYPE.':host='.DB_HOST.';dbname='.DB_NAME; What here causes problem? Usage of constraints? I don't know. My editor (aptana studio) shows error after 1 constant. Thanks

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