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  • [python]: path between two nodes

    - by www.yegorov-p.ru
    I'm using networkx to work with graphs. I have pretty large graph (it's near 200 nodes in it) and I try to find all possible paths between two nodes. But, as I understand, networkx can find only shortest path. How can I get not just shortest path, but all possible paths?

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  • Why isn't my operator overloading working properly?

    - by Mithrax
    I have the following Polynomial class I'm working on: #include <iostream> using namespace std; class Polynomial { //define private member functions private: int coef[100]; // array of coefficients // coef[0] would hold all coefficients of x^0 // coef[1] would hold all x^1 // coef[n] = x^n ... int deg; // degree of polynomial (0 for the zero polynomial) //define public member functions public: Polynomial::Polynomial() //default constructor { for ( int i = 0; i < 100; i++ ) { coef[i] = 0; } } void set ( int a , int b ) //setter function { //coef = new Polynomial[b+1]; coef[b] = a; deg = degree(); } int degree() { int d = 0; for ( int i = 0; i < 100; i++ ) if ( coef[i] != 0 ) d = i; return d; } void print() { for ( int i = 99; i >= 0; i-- ) { if ( coef[i] != 0 ) { cout << coef[i] << "x^" << i << " "; } } } // use Horner's method to compute and return the polynomial evaluated at x int evaluate ( int x ) { int p = 0; for ( int i = deg; i >= 0; i-- ) p = coef[i] + ( x * p ); return p; } // differentiate this polynomial and return it Polynomial differentiate() { if ( deg == 0 ) { Polynomial t; t.set ( 0, 0 ); return t; } Polynomial deriv;// = new Polynomial ( 0, deg - 1 ); deriv.deg = deg - 1; for ( int i = 0; i < deg; i++ ) deriv.coef[i] = ( i + 1 ) * coef[i + 1]; return deriv; } Polynomial Polynomial::operator + ( Polynomial b ) { Polynomial a = *this; //a is the poly on the L.H.S Polynomial c; for ( int i = 0; i <= a.deg; i++ ) c.coef[i] += a.coef[i]; for ( int i = 0; i <= b.deg; i++ ) c.coef[i] += b.coef[i]; c.deg = c.degree(); return c; } Polynomial Polynomial::operator += ( Polynomial b ) { Polynomial a = *this; //a is the poly on the L.H.S Polynomial c; for ( int i = 0; i <= a.deg; i++ ) c.coef[i] += a.coef[i]; for ( int i = 0; i <= b.deg; i++ ) c.coef[i] += b.coef[i]; c.deg = c.degree(); for ( int i = 0; i < 100; i++) a.coef[i] = c.coef[i]; a.deg = a.degree(); return a; } Polynomial Polynomial::operator -= ( Polynomial b ) { Polynomial a = *this; //a is the poly on the L.H.S Polynomial c; for ( int i = 0; i <= a.deg; i++ ) c.coef[i] += a.coef[i]; for ( int i = 0; i <= b.deg; i++ ) c.coef[i] -= b.coef[i]; c.deg = c.degree(); for ( int i = 0; i < 100; i++) a.coef[i] = c.coef[i]; a.deg = a.degree(); return a; } Polynomial Polynomial::operator *= ( Polynomial b ) { Polynomial a = *this; //a is the poly on the L.H.S Polynomial c; for ( int i = 0; i <= a.deg; i++ ) for ( int j = 0; j <= b.deg; j++ ) c.coef[i+j] += ( a.coef[i] * b.coef[j] ); c.deg = c.degree(); for ( int i = 0; i < 100; i++) a.coef[i] = c.coef[i]; a.deg = a.degree(); return a; } Polynomial Polynomial::operator - ( Polynomial b ) { Polynomial a = *this; //a is the poly on the L.H.S Polynomial c; for ( int i = 0; i <= a.deg; i++ ) c.coef[i] += a.coef[i]; for ( int i = 0; i <= b.deg; i++ ) c.coef[i] -= b.coef[i]; c.deg = c.degree(); return c; } Polynomial Polynomial::operator * ( Polynomial b ) { Polynomial a = *this; //a is the poly on the L.H.S Polynomial c; for ( int i = 0; i <= a.deg; i++ ) for ( int j = 0; j <= b.deg; j++ ) c.coef[i+j] += ( a.coef[i] * b.coef[j] ); c.deg = c.degree(); return c; } }; int main() { Polynomial a, b, c, d; a.set ( 7, 4 ); //7x^4 a.set ( 1, 2 ); //x^2 b.set ( 6, 3 ); //6x^3 b.set ( -3, 2 ); //-3x^2 c = a - b; // (7x^4 + x^2) - (6x^3 - 3x^2) a -= b; c.print(); cout << "\n"; a.print(); cout << "\n"; c = a * b; // (7x^4 + x^2) * (6x^3 - 3x^2) c.print(); cout << "\n"; d = c.differentiate().differentiate(); d.print(); cout << "\n"; cout << c.evaluate ( 2 ); //substitue x with 2 cin.get(); } Now, I have the "-" operator overloaded and it works fine: Polynomial Polynomial::operator - ( Polynomial b ) { Polynomial a = *this; //a is the poly on the L.H.S Polynomial c; for ( int i = 0; i <= a.deg; i++ ) c.coef[i] += a.coef[i]; for ( int i = 0; i <= b.deg; i++ ) c.coef[i] -= b.coef[i]; c.deg = c.degree(); return c; } However, I'm having difficulty with my "-=" operator: Polynomial Polynomial::operator -= ( Polynomial b ) { Polynomial a = *this; //a is the poly on the L.H.S Polynomial c; for ( int i = 0; i <= a.deg; i++ ) c.coef[i] += a.coef[i]; for ( int i = 0; i <= b.deg; i++ ) c.coef[i] -= b.coef[i]; c.deg = c.degree(); // overwrite value of 'a' with the newly computed 'c' before returning 'a' for ( int i = 0; i < 100; i++) a.coef[i] = c.coef[i]; a.deg = a.degree(); return a; } I just slightly modified my "-" operator method to overwrite the value in 'a' and return 'a', and just use the 'c' polynomial as a temp. I've put in some debug print statement and I confirm that at the time of computation, both: c = a - b; and a -= b; are computed to the same value. However, when I go to print them, their results are different: Polynomial a, b; a.set ( 7, 4 ); //7x^4 a.set ( 1, 2 ); //x^2 b.set ( 6, 3 ); //6x^3 b.set ( -3, 2 ); //-3x^2 c = a - b; // (7x^4 + x^2) - (6x^3 - 3x^2) a -= b; c.print(); cout << "\n"; a.print(); cout << "\n"; Result: 7x^4 -6x^3 4x^2 7x^4 1x^2 Why is my c = a - b and a -= b giving me different results when I go to print them?

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  • magento getCollection() can we put where condition?

    - by jarus
    hello , i am working on a magento project and i need to get the value according to country wise like select address where country ="Nepal" can we send the where condition in getCollection() function $collection = Mage::getModel('relocator/location')-getCollection(); any help will be appreciated

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  • Listview with copy-paste

    - by Zubirg
    Hi, Is there an easy way of adding copy-paste for a listview, or should I just switch to DataGridView instead? My application is kinda like an address book, it contains emails, numbers etc where copy paste would be useful.

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  • Itertools group by functionality

    - by Nil
    I want to group by on dict key >>> x [{'a': 10, 'b': 90}, {'a': 20}, {'a': 30}, {'a': 10}] >>> [(name, list(group)) for name, group in groupby(x, lambda p:p['a'])] [(10, [{'a': 10, 'b': 90}]), (20, [{'a': 20}]), (30, [{'a': 30}]), (10, [{'a': 10}])] This must group on key 10 :(

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  • Adding values to a C# array

    - by Ross
    Probably a really simple one this - I'm starting out with C# and need to add values to an array, for example: int[] terms; for(int runs = 0; runs < 400; runs++) { terms[] = value; } For those who have used PHP, here's what I'm trying to do in C#: $arr = array(); for ($i = 0; $i < 10; $i++) { $arr[] = $i; } Thanks, Ross

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  • PROLOG all different

    - by inspectorG4dget
    Hello SO, I have a very weird problem with PROLOG. I have used it before, but it's been a while and I'm rusty. I have a list of variables and I need to ensure that none of them are the same. I have tried: use_module(library(bounds)). all_different(A, B, C, D, 6, 8). However, when I try this, I get an error saying that all_different/6 is undefined. How can I go about solving this issue? Is there any library function that I can call directly for this? I am VERY stuck and would greatly appreciate any help. Thanks in advance.

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  • Proper way in Python to raise errors while setting variables

    - by ensnare
    What is the proper way to do error-checking in a class? Raising exceptions? Setting an instance variable dictionary "errors" that contains all the errors and returning it? Is it bad to print errors from a class? Do I have to return False if I'm raising an exception? Just want to make sure that I'm doing things right. Below is some sample code: @property def password(self): return self._password @password.setter def password(self,password): # Check that password has been completed try: # Check that password has a length of 6 characters if (len(password) < 6): raise NameError('Your password must be greater \ than 6 characters') except NameError: print 'Please choose a password' return False except TypeError: print 'Please choose a password' return False #Set the password self._password = password #Encrypt the password password_md5 = md5.new() password_md5.update(password) self._password_md5 = password_md5.hexdigest()

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  • Intro to GPU programming

    - by Adam Davis
    Everyone has this huge massively parallelized supercomputer on their desktop in the form of a graphics card GPU. What is the "hello world" equivalent of the GPU community? What do I do, where do I go, to get started programming the GPU for the major GPU vendors? -Adam

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  • Java: how to use 3rd-party library?

    - by HH
    $ cat MultiTest.java import com.*; // CODE $ javac Code.java MultiTest.java:1: package com does not exist import com.*; ^ Google Collections Com-dir in the dir where the MultiTest.java -file is located.

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  • newbie question -- how does one override show for a newtype?

    - by gatoatigrado
    I want to override the default integer constructors in Haskell so they produce strings (mostly for curiosity, but temporarily to make a nice input alternative for LaTeX's \frac{}{} inconvenience). I wanted to be able to use the language itself, instead of a special parser, but I guess that's probably not going to work out... module Main where import Prelude hiding ((+)) newtype A = A Int deriving (Eq, Show, Num) default (A) (+) :: A -> (A -> String) (A a) + (A b) = (show a) ++ " + " ++ (show b) main2 = 3+4 main :: IO () main = putStrLn main2 The problem with the above is that the + function only works for (A, A) instead of (A, String), etc. If one simply leaves out the pattern match "(A a)" and writes "a" instead, then the show() function prepends "A " so "3" becomes "A 3" instead of just "3". I want to override Show for A, but it seems to be quite a headache...

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  • Proper way to set class variables

    - by ensnare
    I'm writing a class to insert users into a database, and before I get too far in, I just want to make sure that my OO approach is clean: class User(object): def setName(self,name): #Do sanity checks on name self._name = name def setPassword(self,password): #Check password length > 6 characters #Encrypt to md5 self._password = password def commit(self): #Commit to database >>u = User() >>u.setName('Jason Martinez') >>u.setPassword('linebreak') >>u.commit() Is this the right approach? Should I declare class variables up top? Should I use a _ in front of all the class variables to make them private? Thanks for helping out.

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  • python: variable not getting defined after several conditionals

    - by Protean
    For some reason this program is saying that 'switch' is not defined. What is going on? #PYTHON 3.1.1 class mysrt: def __init__(self): self.DATA = open('ORDER.txt', 'r') self.collect = 0 cache1 = str(self.DATA.readlines()) cache2 = [] for i in range(len(cache1)): if cache1[i] == '*': if self.collect == 0: self.collect = 1 elif self.collect == 1: self.collect = 0 elif self.collect == 1: cache2.append(cache1[i]) self.ORDER = cache2 self.ARRAY = [] self.GLOBALi = 0 self.GLOBALmax = range(len(self.ORDER)) self.GLOBALc = [] self.GLOBALl = [] def sorter(self, array): CACHE_LIST_1 = [] CACHE_LIST_2 = [] i = 0 for ORDERi in range(len(self.ORDER)): for ARRAYi in range(len(array)): CACHE = array[ARRAYi] if CACHE[self.GLOBALi] == self.ORDER[ORDERi]: CACHE_LIST_1.append(CACHE) else: CACHE_LIST_2.append(CACHE) for i in range(len(CACHE_LIST_1)): if CACHE_LIST_1[0] == CACHE_LIST_1[i] or range(len(CACHE_LIST_1)) == 1: switch = 1 print ('1') else: switch = 0 print ('0') break if switch == 1: self.GLOBALl += CACHE_LIST_1 + self.GLOBALc self.GLOBALi = 0 self.GLOBALc = [] else: self.GLOBALi += 1 self.GLOBALc += CACHE_LIST_2 mysrt.sorter(CACHE) return (self.GLOBALl) #GLOBALi =0 # if range(len(self.GLOBALc)) =! range(len(self.ARRAY)) array = ['ape', 'cow','dog','bat'] ORDER_FILE = [] mysort = mysrt() print (mysort.sorter(array))

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  • How do you handle key down events on Android? I am having issues making it work.

    - by user279112
    For an Android program, I am having trouble handling key down and key up events, and the problem I am having with them can almost certainly be generalized to any sort of user input event. I am using Lunar Lander as one of my main learning devices as I make my first meaningful program, and I noticed that it was using onKeyDown as an overridden method to receive key down events, and it would call one of their more original methods doKeyDown. But when I tried to implement a very small version of my own onKeyDown overide and the actual handler that it calls, it didn't work. I would probably copy and paste my implementations of those two methods, but that doesn't seem to be the problem. You see, I ran the debugger and noticed that they were not getting called - at all. The same goes for my implementations of onKeyUp and the handler that it calls. Something is a little weird here, and when I tried to look at the Android documentation for it, that didn't help at all. I thought that if you had an overide for onKeyDown, then when a key was pressed during execution of the program, onKeyDown would be called as soon as reasonably possible. End of story. But apparently there's something more to it. Apparently you have to do something else somewhere - possibly in the XML when defining the layout or something - to make it work. But I do not know what, and I could not find what in their documentation. What's the secret to this? Thanks!

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  • Problems with Routing URLs using CGI and Bottle.py

    - by Risingson
    I've been having difficulty getting anything more than a simple index / to return correctly using bottle.py in a CGI environment. When I try to return /hello I get a 404 response. However, if I request /index.py/hello import bottle from bottle import route @route('/') def index(): return 'Index' @route('/hello') def hello(): return 'Hello' if __name__ == '__main__': from wsgiref.handlers import CGIHandler CGIHandler().run(bottle.default_app()) And here is my .htaccess file DirectoryIndex index.py <ifmodule mod_rewrite.c=""> RewriteEngine on RewriteBase / RewriteCond %{REQUEST_FILENAME} !-f RewriteRule ^(.*)$ /index.py/$1 [L] </ifmodule> I copied much of the code from here as I'm using DH and it seemed relevant: http://blog.coderonfire.com/2010/02/running-bottle-python-micro-framework.html Thanks for helping.

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  • Android Custom View Constructor

    - by Mitch
    I'm learning about using Custom Views from the following: http://developer.android.com/guide/topics/ui/custom-components.html#modifying The description says: Class Initialization As always, the super is called first. Furthermore, this is not a default constructor, but a parameterized one. The EditText is created with these parameters when it is inflated from an XML layout file, thus, our constructor needs to both take them and pass them to the superclass constructor as well. Is there a better description? I've been trying to figure out what the constructor(s) should look like and I've come up with 4 possible choices (see example at end of post). I'm not sure what these 4 choices do (or don't do), why I should implement them, or what the parameters mean. Is there a description of these? Thanks. Mitch public MyCustomView() { super(); } public MyCustomView(Context context) { super(context); } public MyCustomView(Context context, AttributeSet attrs) { super(context, attrs); } public MyCustomView(Context context, AttributeSet attrs, Map params) { super(context, attrs, params); }

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  • Store value of os.system or os.popen

    - by chrissygormley
    Hello, I want to grep the error's out of a log file and save the value as an error. When I use: errors = os.system("cat log.txt | grep 'ERROR' | wc -l") I get the return code that the command worked or not. When I use: errors = os.popen("cat log.txt | grep 'ERROR' | wc -l") I get what the command is trying to do. When I run this in the command line I get 3 as thats how many errors there are. Can anyone suggest another way? Thanks

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  • unwanted quote marks in output from printf

    - by Gary
    I have some address data which has been exported from a database. If the address had multiple lines, the exported data has joined all the lines into one string with the former lines being separated by dollars signs. Here's one of the addresses: INFORMATION DELIVERY DEPT$704 CHERRY ST$ATLANTA, GA 30332-0900 I'm splitting this into an array on the dollar sign and outputting the three array elements into separate tab-separated fields with printf. For some reason, it comes out like this: INFORMATION DELIVERY DEPT 704 CHERRY ST "ATLANTA, GA 30332-0900" I don't want the quotes around that final field. Can anyone explain why this is happening and how to suppress it? This is being done in Windows Vista with gawk3.1.6. Thanks! gary

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  • Regex: Use start of line/end of line signs (^ or $) in different context

    - by fgysin
    While doing some small regex task I came upon this problem. I have a string that is a list of tags that looks e.g like this: foo,bar,qux,garp,wobble,thud What I needed to do was to check if a certain tag, e.g. 'garp' was in this list. (What it finally matches is not really important, just if there is a match or not.) My first and a bit stupid try at this was to use the following regex: [^,]garp[,$] My idea was that before 'garp' there should either be the start of the line/string or a comma, after 'garp' there should be either a comma or the end of the line/string. Now, it is instantly obvious that this regex is wrong: Both ^ and $ change their behaviour in the context of the character class [ ]. What I finally came up with is the following: ^garp$|^garp,|,garp,|,garp$ This regex just handles the 4 cases one by one. (Tag at beginning of list, in the center, at the end, or as the only element of the list.) The last regex is somehow a bit ugly in my eyes and just for funs sake I'd like to make it a bit more elegant. Is there a way how the start of line/end of line characters (^ and $) can be used in the context of character classes?

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  • What is the coolest thing you can do in <10 lines of simple code? Help me inspire beginners!

    - by Tom Ritter
    I'm looking for the coolest thing you can do in a few lines of simple code. I'm sure you can write a Mandelbrot set in Haskell in 15 lines but it's difficult to follow. My goal is to inspire students that programming is cool. We know that programming is cool because you can create anything you imagine - it's the ultimate creative outlet. I want to inspire these beginners and get them over as many early-learning humps as I can. Now, my reasons are selfish. I'm teaching an Intro to Computing course to a group of 60 half-engineering, half business majors; all freshmen. They are the students who came from underprivileged High schools. From my past experience, the group is generally split as follows: a few rock-stars, some who try very hard and kind of get it, the few who try very hard and barely get it, and the few who don't care. I want to reach as many of these groups as effectively as I can. Here's an example of how I'd use a computer program to teach: Here's an example of what I'm looking for: a 1-line VBS script to get your computer to talk to you: CreateObject("sapi.spvoice").Speak InputBox("Enter your text","Talk it") I could use this to demonstrate order of operations. I'd show the code, let them play with it, then explain that There's a lot going on in that line, but the computer can make sense of it, because it knows the rules. Then I'd show them something like this: 4(5*5) / 10 + 9(.25 + .75) And you can see that first I need to do is (5*5). Then I can multiply for 4. And now I've created the Object. Dividing by 10 is the same as calling Speak - I can't Speak before I have an object, and I can't divide before I have 100. Then on the other side I first create an InputBox with some instructions for how to display it. When I hit enter on the input box it evaluates or "returns" whatever I entered. (Hint: 'oooooo' makes a funny sound) So when I say Speak, the right side is what to Speak. And I get that from the InputBox. So when you do several things on a line, like: x = 14 + y; You need to be aware of the order of things. First we add 14 and y. Then we put the result (what it evaluates to, or returns) into x. That's my goal, to have a bunch of these cool examples to demonstrate and teach the class while they have fun. I tried this example on my roommate and while I may not use this as the first lesson, she liked it and learned something. Some cool mathematica programs that make beautiful graphs or shapes that are easy to understand would be good ideas and I'm going to look into those. Here are some complicated actionscript examples but that's a bit too advanced and I can't teach flash. What other ideas do you have?

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  • Single-player pong game

    - by Jam
    I am just starting out learning pygame and livewires, and I'm trying to make a single-player pong game, where you just hit the ball, and it bounces around until it passes your paddle (located on the left side of the screen and controlled by the mouse), which makes you lose. However, I keep getting the error: "Cannot have more than on Screen object", which I can find no references to online really, and I can't make sense of it. I want to eventually make the game more complicated, but I need to make it work first. Help please! Here's the code so far: from livewires import games games.init(screen_width=640, screen_height=480, fps=50) class Paddle(games.Sprite): image=games.load_image("paddle.bmp") def __init__(self): super(Paddle, self).__init__(image=Paddle.image, y=games.mouse.y, left=0) self.score=games.Text(value=0, size=25, top=5, right=games.screen.width-10) games.screen.add(self.score) def update(self): self.y=games.mouse.y self.check_collide() def check_collide(self): for ball in self.overlapping_sprites: self.score.value+=1 self.score.right=games.screen.width-10 ball.handle_collide() class Ball(games.Sprite): image=games.load_image("ball.bmp") speed=1 def __init__(self, x, y=90): super(Ball, self).__init__(image=Ball.image, x=x, y=y, dx=Ball.speed, dy=Ball.speed) def update(self): if self.left<0: self.end_game() self.destroy() def handle_collide(self): if self.right>games.screen.width: self.dx=-self.dx if self.bottom>games.screen.height or self.top<0: self.dy=-self.dy def ball_destroy(self): self.destroy() def main(): background_image=games.load_image("background.bmp", transparent=False) games.screen.background=background_image the_ball=Ball() games.screen.add(the_ball) the_paddle=Paddle() games.screen.add(the_paddle) games.mouse.is_visible=False games.screen.event_grab=True games.screen.mainloop() main()

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  • Newbie question about Java

    - by Rob Nicholson
    Okay, I know that Java is a language but somebody has asked me if they can write a web application to interface in with a web app I've written in ASP.NET. I'm implementing a web service to serve up an XML so it's pretty language agnostic. However, I'm not 100% sure whether going down the Java route makes a lot of sense. I was kind of expecting PHP or ASP.NET server side code with maybe some Ajax/JavaScript or maybe a heavier client JavaScript program using JScript. Could some kind sole explain the basic Java environment when it comes with webapps. I've inferred the following - am I barking up the right tree? Java when run like ASP.NET is called JSP JavaBeans is a bit like the .NET framework, i.e. it's a library of re-usable components Java EE is a bit like ASP.NET in that it's a framework for building web pages on a server Java can also run on the client but it needs the Java VM installing When running Java on the client, can you use JavaBeans and is there a framework? Can it also use JScript? I don't think so as JScript is JavaScript library. Whilst running Java on the server would be okay, this is a relatively small application and therefore Java sounds like a bit of overkill. PHP or ASP.NET feels a better fit. But I don't think they should go down the Java applet in the browser and it adds complexity that's not needed. Thanks, Rob.

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  • Getting Started with Python: Attribute Error

    - by Nacari
    I am new to python and just downloaded it today. I am using it to work on a web spider, so to test it out and make sure everything was working, I downloaded a sample code. Unfortunately, it does not work and gives me the error: "AttributeError: 'MyShell' object has no attribute 'loaded' " I am not sure if the code its self has an error or I failed to do something correctly when installing python. Is there anything you have to do when installing python like adding environmental variables, etc.? And what does that error generally mean? Here is the sample code I used with imported spider class: import chilkat spider = chilkat.CkSpider() spider.Initialize("www.chilkatsoft.com") spider.AddUnspidered("http://www.chilkatsoft.com/") for i in range(0,10): success = spider.CrawlNext() if (success == True): print spider.lastUrl() else: if (spider.get_NumUnspidered() == 0): print "No more URLs to spider" else: print spider.lastErrorText() # Sleep 1 second before spidering the next URL. spider.SleepMs(1000)

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