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  • printing the instance in Python

    - by kame
    Hello! With this code: class Complex: def __init__(self, realpart, imagpart): self.real = realpart self.imag = imagpart print self.real, self.imag class Circle: def __init__(self, radius): print "A circle wiht the radius", radius, "has the properties:" print "circumference =", 3.14*radius print "area =", 3.14*radius**2 I get this output: >>> Complex(3,2) 3 2 <__main__.Complex instance at 0x01412210> But why does he print the last line?

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  • Using object's method as callback function for $.post

    - by Kirzilla
    Hello, $.Comment = function() { this.alertme = "Alert!"; } $.Comment.prototype.send = function() { var self = this; $.post( self.url, { 'somedata' : self.somedata }, function(data, self) { self.callback(data); } ); } $.Comment.prototype.callback = function(data) { alert(this.alertme); } When I'm calling $.Comment.send() debugger is saying to me that self.callback(data) is not a function What am I doing wrong? Thank you

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  • User HasOne ActiveToken, HasMany Tokens, how to setup in Rails?

    - by viatropos
    I have two simple models: class User < ActiveRecord::Base has_many :tokens # has_one doesn't work, because Token already stores # foreign id to user... # has_one :active_token, :class_name => "Token" # belongs_to doesn't work because Token belongs to # User already, and they both can't belong to each other # belongs_to :active_token, :class_name => "Token" end class Token < ActiveRecord::Base belongs_to :user end I want to say "User has_one :active_token, :class_name => 'Token'", but I can't because Token already belongs_to User. What I did instead was just manually add similar functionality to the user like so: class User < ActiveRecord::Base has_many :tokens attr_accessor :active_token after_create :save_active_token before_destroy :destroy_active_token # it belongs_to, but you can't have both belongs_to each other... def active_token return nil unless self.active_token_id @active_token ||= Token.find(self.active_token_id) end def active_token=(value) self.active_token_id = value.id @active_token = value end def save_active_token self.active_token.user = self self.active_token.save end def destroy_active_token self.active_token.destroy if self.active_token end end Is there a better way?

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  • How to generate links to the android Classes' reference in javadoc ?

    - by Kaillash
    Hi, When I generate Javadoc for my android project in eclipse, there are lots of warnings like cannot find symbol symbol : class TextView and warning - Tag @see: reference not found: android.app.Dialog I also tried -link http://developer.android.com/reference/ -link http://java.sun.com/j2se/1.4.2/docs/api/ in Extra javadoc options tab in Configure Javadoc Arguments dialog of eclipse-Export Javadoc. But only -link http://java.sun.com/j2se/1.4.2/docs/api/ is working i.e for String class link http://java.sun.com/j2se/1.4.2/docs/api/java/lang/String.html?is-external=true is generated. but for android.app.Dialog , no link is generated. Please help !!

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  • threading in Python taking up too much CPU

    - by KevinShaffer
    I wrote a chat program and have a GUI running using Tkinter, and to go and check when new messages have arrived, I create a new thread so Tkinter keeps doing its thing without locking up while the new thread goes and grabs what I need and updates the Tkinter window. This however becomes a huge CPU hog, and my guess is that it has to do somehow with the fact that the Thread is started and never really released when the function is done. Here's the relevant code (it's ugly and not optimized at the moment, but it gets the job done, and itself does not use too much processing power, as when I run it not threaded, it doesn't take up much CPU but it locks up Tkinter) Note: This is inside of a class, hence the extra tab. def interim(self): threading.Thread(target=self.readLog).start() self.after(5000,self.interim) def readLog(self): print 'reading' try: length = len(str(self.readNumber)) f = open('chatlog'+str(myport),'r') temp = f.readline().replace('\n','') while (temp[:length] != str(self.readNumber)) or temp[0] == '<': temp = f.readline().replace('\n','') while temp: if temp[0] != '<': self.updateChat(temp[length:]) self.readNumber +=1 else: self.updateChat(temp) temp = f.readline().replace('\n','') f.close() Is there a way to better manage the threading so I don't consume 100% of the CPU very quickly?

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  • Excel - Dynamic reference based on the row I paste into?

    - by michaelmichael
    I have a simple, oft-used formula that I paste into spreadsheets I receive. It looks like this: =IF(AND(D8="COMPLETE",E8=""),A8,"") It looks in D8 for the word "COMPLETE" and checks that E8 is blank. If both conditions are fulfilled it grabs the contents of A8. It works fine. The only problem with this is that I don't always paste it into row 8. Every spreadsheet is different. I usually end up spending a few seconds making the formula fit the current spreadsheet I'm working on by dragging the cell references to the appropriate row. Hence, my question: Is there a way to make an absolute row reference based on whatever row I paste into? For example, if I paste the above formula into a cell in row 25, the formula would automatically look like this: =IF(AND(D25="COMPLETE", E25=""), A25, "")

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  • Tkinter mouse event initially triggered

    - by user3714884
    I'm currently learning Tkinter and I cannot find a solution for my problem here nor outside Stackoverflow. In a nutshell, all events that I bind to my widgets are triggered initialy and don't respond to my actions. In this example, the red rectangle appears on the canvas when I run the code, and color=random.choice(['red', 'blue']) revealed that the event binding doesn't work after that: import Tkinter as tk class application(tk.Frame): def __init__(self, master=None): tk.Frame.__init__(self, master) self.can = tk.Canvas(master, width=200, height=200) self.can.bind('<Button-2>', self.draw()) self.can.grid() def draw(self): self.can.create_rectangle(50, 50, 100, 100, fill='red') app = application() app.mainloop() I use a Mac platform, but I haven't got a clue about its role in the problem. Could anyone please point me at the mistake i did here?

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  • How to retrieve items from a django queryset?

    - by sharataka
    I'm trying to get the video element in a queryset but am having trouble retrieving it. user_channel = Everything.objects.filter(profile = request.user, playlist = 'Channel') print user_channel[0] #returns the first result without error print user_channel[0]['video'] #returns error Models.py: class Everything(models.Model): profile = models.ForeignKey(User) playlist = models.CharField('Playlist', max_length = 2000, null=True, blank=True) platform = models.CharField('Platform', max_length = 2000, null=True, blank=True) video = models.CharField('VideoID', max_length = 2000, null=True, blank=True) video_title = models.CharField('Title of Video', max_length = 2000, null=True, blank=True) def __unicode__(self): return u'%s %s %s %s %s' % (self.profile, self.playlist, self.platform, self.video, self.video_title)

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  • How to get text in QlineEdit when QpushButton is pressed in a string?

    - by esafwan
    I have given my code below, have problem in implementing a function I want the text in lineedit with objectname 'host' in a string say 'shost'. when the user click the pushbutton with name 'connect'.How do i do it? I tried and failed. How to implement this function? import sys from PyQt4.QtCore import * from PyQt4.QtGui import * class Form(QDialog): def __init__(self, parent=None): super(Form, self).__init__(parent) le = QLineEdit() le.setObjectName("host") le.setText("Host") pb = QPushButton() pb.setObjectName("connect") pb.setText("Connect") layout.addWidget(le) layout.addWidget(pb) self.setLayout(layout) self.connect(pb, SIGNAL("clicked()"),self.button_click) self.setWindowTitle("Learning") def button_click(self): #i want the text in lineedit with objectname #'host' in a string say 'shost'. when the user click # the pushbutton with name connect.How do i do it? # I tried and failed. How to implement this function? app = QApplication(sys.argv) form = Form() form.show() app.exec_() Now how do i implement the function "def button_click(self):" ? I have just started with pyQt!

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  • Class Template Instantiation: any way round this circular reference?

    - by TimYorke34
    I have two classes that I'm using to represent some hardware: A Button and an InputPin class which represent a button that will change the value of an IC's input pin when it's pressed down. A simple example of them is: template <int pinNumber> class InputPin { static bool IsHigh() { return ( (*portAddress) & (1<<pinNumber) ); } }; template <typename InputPin> class Button { static bool IsPressed() { return !InputPin::IsHigh(); } }; This works beautifully and by using class templates, the condition below will compile as tightly as if I'd handwritten it in assembly (a single instruction). Button < InputPin<1> > powerButton; if (powerButton.IsPressed()) ........; However, I am extending it to deal with interrupts and have got a problem with circular references. Compared to the original InputPin, a new InputPinIRQ class has an extra static member function that will be called automatically by the hardware when the pin value changes. I'd like it to be able to notify the Button class of this, so that the Button class can then notify the main application that it has been pressed/released. I am currently doing this with function pointers to callbacks. In order for the callback code to be inlined by the compiler, I need to pass the function pointers as template parameters. So now, both of the new classes have an extra template parameter that is a pointer to a callback function. Unfortunately this gives me a circular reference because to instantiate a ButtonIRQ class I now have to do something like this: ButtonIRQ< InputPinIRQ< A1, ButtonIRQ<....>::OnPinChange, OnButtonChange > pB; where the <...... represents the circular reference. Does anyone know how I can avoid this circular reference? I am new to templates, so might be missing something really simple. It's important that the compiler knows exactly what code will be run when the interrupt occurs as it then does some very useful optimisation - it is able to inline the callback function and literally inserts the callback function's code at the exact address that is called on a h/w interrupt.

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  • Why does the assignment operator return a value and not a reference?

    - by Nick Lowman
    I saw the example below explained on this site and thought both answers would be 20 and not the 10 that is returned. He wrote that both the comma and assignment returns a value, not a reference. I don't quite understand what that means. I understand it in relation to passing variables into functions or methods i.e primitive types are passed in by value and objects by reference but I'm not sure how it applies in this case. I also understand about context and the value of 'this' (after help from stackoverflow) but I thought in both cases I would still be invoking it as a method, foo.bar() which would mean foo is the context but it seems both result in a function call bar(). Why is that and what does it all mean? var x = 10; var foo = { x: 20, bar: function () {return this.x;} }; (foo.bar = foo.bar)();//returns 10 (foo.bar, foo.bar)();//returns 10

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  • Problem with SIngleton Class

    - by zp26
    Hi, I have a prblem with my code. I have a viewController and a singleton class. When i call the method readXml and run a for my program update the UITextView. When i call the clearTextView method the program exit with EXC_BAD_ACCESS. The prblem it's the name of the variable position. This is invalid but i don't change anything between the two methods. You have an idea? My code: #import "PositionIdentifierViewController.h" #import "WriterXML.h" #import "ParserXML.h" #define timeToScan 0.1 @implementation PositionIdentifierViewController @synthesize accelerometer; @synthesize actualPosition; @synthesize actualX; @synthesize actualY; @synthesize actualZ; -(void)updateTextView:(NSString*)nomePosizione { NSString *string = [NSString stringWithFormat:@"%@",nomePosizione]; textEvent.text = [textEvent.text stringByAppendingString:@"\n"]; textEvent.text = [textEvent.text stringByAppendingString:string]; } -(IBAction)clearTextEvent{ textEvent.text = @""; //with this for my program exit for(int i=0; i<[[sharedController arrayPosition]count]; i++){ NSLog(@"sononelfor"); Position *tempPosition = [[Position alloc]init]; tempPosition = [[sharedController arrayPosition]objectAtIndex:i]; [self updateTextView:(NSString*)[tempPosition name]]; } } -(void)readXml{ if([sharedController readXml]){ UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Caricamento Posizioni" message:@"Caricamento effettuato con successo" delegate:self cancelButtonTitle:@"Cancel" otherButtonTitles:nil]; [alert show]; [alert release]; NSString *string = [NSString stringWithFormat:@"%d", [[sharedController arrayPosition]count]]; [self updateTextView:(NSString*)string]; //with only this the program is ok for(int i=0; i<[[sharedController arrayPosition]count]; i++){ NSLog(@"sononelfor"); Position *tempPosition = [[Position alloc]init]; tempPosition = [[sharedController arrayPosition]objectAtIndex:i]; [self updateTextView:(NSString*)[tempPosition name]]; } } else{ UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Caricamento Posizioni" message:@"Caricamento non riuscito" delegate:self cancelButtonTitle:@"Cancel" otherButtonTitles:nil]; [alert show]; [alert release]; } } // Implement viewDidLoad to do additional setup after loading the view, typically from a nib. - (void)viewDidLoad { [super viewDidLoad]; sharedController = [SingletonController sharedSingletonController]; actualPosition = [[Position alloc]init]; self.accelerometer = [UIAccelerometer sharedAccelerometer]; self.accelerometer.updateInterval = timeToScan; self.accelerometer.delegate = self; actualX=0; actualY=0; actualZ=0; [self readXml]; } - (void)dealloc { [super dealloc]; [actualPosition dealloc]; [super dealloc]; } @end #import "SingletonController.h" #import "Position.h" #import "WriterXML.h" #import "ParserXML.h" #define standardSensibility 2 #define timeToScan .1 @implementation SingletonController @synthesize arrayPosition; @synthesize arrayMovement; @synthesize actualPosition; @synthesize actualMove; @synthesize stopThread; +(SingletonController*)sharedSingletonController{ static SingletonController *sharedSingletonController; @synchronized(self) { if(!sharedSingletonController){ sharedSingletonController = [[SingletonController alloc]init]; } } return sharedSingletonController; } -(BOOL)readXml{ ParserXML *newParser = [[ParserXML alloc]init]; if([newParser startParsing:(NSString*)@"filePosizioni.xml"]){ [arrayPosition addObjectsFromArray:[newParser arrayPosition]]; return TRUE; } else return FALSE; } -(id)init{ self = [super init]; if (self != nil) { arrayPosition = [[NSMutableArray alloc]init]; arrayMovement = [[NSMutableArray alloc]init]; actualPosition = [[Position alloc]init]; actualMove = [[Movement alloc]init]; stopThread = FALSE; } return self; } -(void) dealloc { [super dealloc]; } @end

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  • How to call a method after asynchronous task is complete

    - by doctordoder
    I have a class called WikiWebView which is a subclass of UIWebView which loads Wikipedia subjects and is designed to fetch all the links of the webpage, in order to create a sort of site map for the subject. My problem is that I can only create the links once the web page has loaded, but the loading isn't done right after [self loadRequest:requestObj] is called. - (void)loadSubject:(NSString *)subject { // load the actual webpage NSString *wiki = @"http://www.wikipedia.org/wiki/"; NSString *fullURL = [wiki stringByAppendingString:subject]; NSURL *url = [NSURL URLWithString:fullURL]; NSURLRequest *requestObj = [NSURLRequest requestWithURL:url]; [self loadRequest:requestObj]; // [self createLinks]; // need this to be called after the view has loaded } - (void)createLinks { NSString *javascript = @"var string = \"\";" "var arr = document.getElementsByClassName(\"mw-redirect\");" "for (var i = 0; i < arr.length; ++i)" "{" "var redirectLink = arr[i].href;" "string = string + redirectLink + \" \";" "}" "string;"; NSString *links = [self stringByEvaluatingJavaScriptFromString:javascript]; self.links = [links componentsSeparatedByString:@" "]; } I tried the normal delegation technique, which lead to this code being added: - (id)init { if (self = [super init]) { self.delegate = self; // weird } return self; } #pragma mark - UIWebViewDelegate - (void)webViewDidStartLoad:(UIWebView *)webView { ++_numProcesses; } - (void)webView:(UIWebView *)webView didFailLoadWithError:(NSError *)error { --_numProcesses; } - (void)webViewDidFinishLoad:(UIWebView *)webView { --_numProcesses; if (_numProcesses == 0) { [self createLinks]; } } However, the delegate methods are never called.. I've seen similar questions where the answers are to use blocks, but how would I do that in this case?

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  • Programmatic binding of accelerators in wxPython

    - by Inductiveload
    I am trying to programmatically create and bind a table of accelerators in wxPython in a loop so that I don't need to worry about getting and assigning new IDs to each accelerators (and with a view to inhaling the handler list from some external resource, rather than hard-coding them). I also pass in some arguments to the handler via a lambda since a lot of my handlers will be the same but with different parameters (move, zoom, etc). The class is subclassed from wx.Frame and setup_accelerators() is called during initialisation. def setup_accelerators(self): bindings = [ (wx.ACCEL_CTRL, wx.WXK_UP, self.on_move, 'up'), (wx.ACCEL_CTRL, wx.WXK_DOWN, self.on_move, 'down'), (wx.ACCEL_CTRL, wx.WXK_LEFT, self.on_move, 'left'), (wx.ACCEL_CTRL, wx.WXK_RIGHT, self.on_move, 'right'), ] accelEntries = [] for binding in bindings: eventId = wx.NewId() accelEntries.append( (binding[0], binding[1], eventId) ) self.Bind(wx.EVT_MENU, lambda event: binding[2](event, binding[3]), id=eventId) accelTable = wx.AcceleratorTable(accelEntries) self.SetAcceleratorTable(accelTable) def on_move(self, e, direction): print direction However, this appears to bind all the accelerators to the last entry, so that Ctrl+Up prints "right", as do all the other three. How to correctly bind multiple handlers in this way?

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  • Are there concurrency problems when using -performSelector:withObject:afterDelay: ?

    - by mystify
    For example, I often use this: [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:someDelay]; Now, lets say I call this 10 times to perform at the exact same delay, like: [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; - (void)doSomethingAfterDelay:(id)someObject { /* access an array, read stuff, write stuff, do different things that would suffer in multithreaded environments .... all operations are nonatomic! */ } I have observed pretty strange behavior when doing things like this. For my understanding, this method schedules a timer to fire on the current thread, so in this case the main thread. But since it doesn't create new threads, it actually should not be possible to run into concurrency problems, right?

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  • Are there concurrency problems when using -performSelector:withObject:afterDelay: ?

    - by mystify
    For example, I often use this: [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:someDelay]; Now, lets say I call this 10 times to perform at the exact same delay, like: [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; - (void)doSomethingAfterDelay:(id)someObject { /* access an array, read stuff, write stuff, do different things that would suffer in multithreaded environments .... all operations are nonatomic! */ } I have observed pretty strange behavior when doing things like this. For my understanding, this method schedules a timer to fire on the current thread, so in this case the main thread. But since it doesn't create new threads, it actually should not be possible to run into concurrency problems, right?

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  • Python Class Variables Question

    - by zyq524
    I have some doubt about python's class variables. As my understanding, if I define a class variable, which is declared outside the init() function, this variable will create only once as a static variable in C++. This seems right for some python types, for instance, dict and list type, but for those base type, e.g. int,float, is not the same. For example: class A: dict1={} list1=list() int1=3 def add_stuff(self, k, v): self.dict1[k]=v self.list1.append(k) self.int1=k def print_stuff(self): print self.dict1,self.list1,self.int1 a1 = A() a1.add_stuff(1, 2) a1.print_stuff() a2=A() a2.print_stuff() The output is: {1: 2} [1] 1 {1: 2} [1] 3 I understand the results of dict1 and list1, but why does int1 behavior different?

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  • I can get access to object's properties if method is called from anonymous function, but I can't do

    - by Kirzilla
    Hello, $.Comment = function() { this.alertme = "Alert!"; } $.Comment.prototype.send = function() { var self = this; $.post( self.url, { 'somedata' : self.somedata }, function(data) { //using anonymous function to call object's method self.callback(data); } ); } $.Comment.prototype.callback = function(data) { alert(this.alertme); } This code works great when I'm calling $.Comment.send(), but this code won't work... $.Comment.prototype.send = function() { var self = this; $.post( self.url, { 'somedata' : self.somedata }, self.callback //using direct access to method ); } Please, could you explain me why? Thank you

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  • method works fine, until it is called in a function, then UnboundLocalError

    - by user1776100
    I define a method called dist, to calculate the distance between two points which I does it correctly when directly using the method. However, when I get a function to call it to calculate the distance between two points, I get UnboundLocalError: local variable 'minkowski_distance' referenced before assignment edit sorry, I just realised, this function does work. However I have another method calling it that doesn't. I put the last method at the bottom This is the method: class MinkowskiDistance(Distance): def __init__(self, dist_funct_name_str = 'Minkowski distance', p=2): self.p = p def dist(self, obj_a, obj_b): distance_to_power_p=0 p=self.p for i in range(len(obj_a)): distance_to_power_p += abs((obj_a[i]-obj_b[i]))**(p) minkowski_distance = (distance_to_power_p)**(1/p) return minkowski_distance and this is the function: (it basically splits the tuples x and y into their number and string components and calculates the distance between the numeric part of x and y and then the distance between the string parts, then adds them. def total_dist(x, y, p=2, q=2): jacard = QGramDistance(q=q) minkowski = MinkowskiDistance(p=p) x_num = [] x_str = [] y_num = [] y_str = [] #I am spliting each vector into its numerical parts and its string parts so that the distances #of each part can be found, then summed together. for i in range(len(x)): if type(x[i]) == float or type(x[i]) == int: x_num.append(x[i]) y_num.append(y[i]) else: x_str.append(x[i]) y_str.append(y[i]) num_dist = minkowski.dist(x_num,y_num) str_dist = I find using some more steps #I am simply adding the two types of distance to get the total distance: return num_dist + str_dist class NearestNeighbourClustering(Clustering): def __init__(self, data_file, clust_algo_name_str='', strip_header = "no", remove = -1): self.data_file= data_file self.header_strip = strip_header self.remove_column = remove def run_clustering(self, max_dist, p=2, q=2): K = {} #dictionary of clusters data_points = self.read_data_file() K[0]=[data_points[0]] k=0 #I added the first point in the data to the 0th cluster #k = number of clusters minus 1 n = len(data_points) for i in range(1,n): data_point_in_a_cluster = "no" for c in range(k+1): distances_from_i = [total_dist(data_points[i],K[c][j], p=p, q=q) for j in range(len(K[c]))] d = min(distances_from_i) if d <= max_dist: K[c].append(data_points[i]) data_point_in_a_cluster = "yes" if data_point_in_a_cluster == "no": k += 1 K[k]=[data_points[i]] return K

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  • Creating HTML5 Offline Web Applications with ASP.NET

    - by Stephen Walther
    The goal of this blog entry is to describe how you can create HTML5 Offline Web Applications when building ASP.NET web applications. I describe the method that I used to create an offline Web application when building the JavaScript Reference application. You can read about the HTML5 Offline Web Application standard by visiting the following links: Offline Web Applications Firefox Offline Web Applications Safari Offline Web Applications Currently, the HTML5 Offline Web Applications feature works with all modern browsers with one important exception. You can use Offline Web Applications with Firefox, Chrome, and Safari (including iPhone Safari). Unfortunately, however, Internet Explorer does not support Offline Web Applications (not even IE 9). Why Build an HTML5 Offline Web Application? The official reason to build an Offline Web Application is so that you do not need to be connected to the Internet to use it. For example, you can use the JavaScript Reference Application when flying in an airplane, riding a subway, or hiding in a cave in Borneo. The JavaScript Reference Application works great on my iPhone even when I am completely disconnected from any network. The following screenshot shows the JavaScript Reference Application running on my iPhone when airplane mode is enabled (notice the little orange airplane):   Admittedly, it is becoming increasingly difficult to find locations where you can’t get Internet access. A second, and possibly better, reason to create Offline Web Applications is speed. An Offline Web Application must be downloaded only once. After it gets downloaded, all of the files required by your Web application (HTML, CSS, JavaScript, Image) are stored persistently on your computer. Think of Offline Web Applications as providing you with a super browser cache. Normally, when you cache files in a browser, the files are cached on a file-by-file basis. For each HTML, CSS, image, or JavaScript file, you specify how long the file should remain in the cache by setting cache headers. Unlike the normal browser caching mechanism, the HTML5 Offline Web Application cache is used to specify a caching policy for an entire set of files. You use a manifest file to list the files that you want to cache and these files are cached until the manifest is changed. Another advantage of using the HTML5 offline cache is that the HTML5 standard supports several JavaScript events and methods related to the offline cache. For example, you can be notified in your JavaScript code whenever the offline application has been updated. You can use JavaScript methods, such as the ApplicationCache.update() method, to update the cache programmatically. Creating the Manifest File The HTML5 Offline Cache uses a manifest file to determine the files that get cached. Here’s what the manifest file looks like for the JavaScript Reference application: CACHE MANIFEST # v30 Default.aspx # Standard Script Libraries Scripts/jquery-1.4.4.min.js Scripts/jquery-ui-1.8.7.custom.min.js Scripts/jquery.tmpl.min.js Scripts/json2.js # App Scripts App_Scripts/combine.js App_Scripts/combine.debug.js # Content (CSS & images) Content/default.css Content/logo.png Content/ui-lightness/jquery-ui-1.8.7.custom.css Content/ui-lightness/images/ui-bg_glass_65_ffffff_1x400.png Content/ui-lightness/images/ui-bg_glass_100_f6f6f6_1x400.png Content/ui-lightness/images/ui-bg_highlight-soft_100_eeeeee_1x100.png Content/ui-lightness/images/ui-icons_222222_256x240.png Content/ui-lightness/images/ui-bg_glass_100_fdf5ce_1x400.png Content/ui-lightness/images/ui-bg_diagonals-thick_20_666666_40x40.png Content/ui-lightness/images/ui-bg_gloss-wave_35_f6a828_500x100.png Content/ui-lightness/images/ui-icons_ffffff_256x240.png Content/ui-lightness/images/ui-icons_ef8c08_256x240.png Content/browsers/c8.png Content/browsers/es3.png Content/browsers/es5.png Content/browsers/ff3_6.png Content/browsers/ie8.png Content/browsers/ie9.png Content/browsers/sf5.png NETWORK: Services/EntryService.svc http://superexpert.com/resources/JavaScriptReference/ A Cache Manifest file always starts with the line of text Cache Manifest. In the manifest above, all of the CSS, image, and JavaScript files required by the JavaScript Reference application are listed. For example, the Default.aspx ASP.NET page, jQuery library, JQuery UI library, and several images are listed. Notice that you can add comments to a manifest by starting a line with the hash character (#). I use comments in the manifest above to group JavaScript and image files. Finally, notice that there is a NETWORK: section of the manifest. You list any file that you do not want to cache (any file that requires network access) in this section. In the manifest above, the NETWORK: section includes the URL for a WCF Service named EntryService.svc. This service is called to get the JavaScript entries displayed by the JavaScript Reference. There are two important things that you need to be aware of when using a manifest file. First, all relative URLs listed in a manifest are resolved relative to the manifest file. The URLs listed in the manifest above are all resolved relative to the root of the application because the manifest file is located in the application root. Second, whenever you make a change to the manifest file, browsers will download all of the files contained in the manifest (all of them). For example, if you add a new file to the manifest then any browser that supports the Offline Cache standard will detect the change in the manifest and download all of the files listed in the manifest automatically. If you make changes to files in the manifest (for example, modify a JavaScript file) then you need to make a change in the manifest file in order for the new version of the file to be downloaded. The standard way of updating a manifest file is to include a comment with a version number. The manifest above includes a # v30 comment. If you make a change to a file then you need to modify the comment to be # v31 in order for the new file to be downloaded. When Are Updated Files Downloaded? When you make changes to a manifest, the changes are not reflected the very next time you open the offline application in your web browser. Your web browser will download the updated files in the background. This can be very confusing when you are working with JavaScript files. If you make a change to a JavaScript file, and you have cached the application offline, then the changes to the JavaScript file won’t appear when you reload the application. The HTML5 standard includes new JavaScript events and methods that you can use to track changes and make changes to the Application Cache. You can use the ApplicationCache.update() method to initiate an update to the application cache and you can use the ApplicationCache.swapCache() method to switch to the latest version of a cached application. My heartfelt recommendation is that you do not enable your application for offline storage until after you finish writing your application code. Otherwise, debugging the application can become a very confusing experience. Offline Web Applications versus Local Storage Be careful to not confuse the HTML5 Offline Web Application feature and HTML5 Local Storage (aka DOM storage) feature. The JavaScript Reference Application uses both features. HTML5 Local Storage enables you to store key/value pairs persistently. Think of Local Storage as a super cookie. I describe how the JavaScript Reference Application uses Local Storage to store the database of JavaScript entries in a separate blog entry. Offline Web Applications enable you to store static files persistently. Think of Offline Web Applications as a super cache. Creating a Manifest File in an ASP.NET Application A manifest file must be served with the MIME type text/cache-manifest. In order to serve the JavaScript Reference manifest with the proper MIME type, I added two files to the JavaScript Reference Application project: Manifest.txt – This text file contains the actual manifest file. Manifest.ashx – This generic handler sends the Manifest.txt file with the MIME type text/cache-manifest. Here’s the code for the generic handler: using System.Web; namespace JavaScriptReference { public class Manifest : IHttpHandler { public void ProcessRequest(HttpContext context) { context.Response.ContentType = "text/cache-manifest"; context.Response.WriteFile(context.Server.MapPath("Manifest.txt")); } public bool IsReusable { get { return false; } } } } The Default.aspx file contains a reference to the manifest. The opening HTML tag in the Default.aspx file looks like this: <html manifest="Manifest.ashx"> Notice that the HTML tag contains a manifest attribute that points to the Manifest.ashx generic handler. Internet Explorer simply ignores this attribute. Every other modern browser will download the manifest when the Default.aspx page is requested. Seeing the Offline Web Application in Action The experience of using an HTML5 Web Application is different with different browsers. When you first open the JavaScript Reference application with Firefox, you get the following warning: Notice that you are provided with the choice of whether you want to use the application offline or not. Browsers other than Firefox, such as Chrome and Safari, do not provide you with this choice. Chrome and Safari will create an offline cache automatically. If you click the Allow button then Firefox will download all of the files listed in the manifest. You can view the files contained in the Firefox offline application cache by typing about:cache in the Firefox address bar: You can view the actual items being cached by clicking the List Cache Entries link: The Offline Web Application experience is different in the case of Google Chrome. You can view the entries in the offline cache by opening the Developer Tools (hit Shift+CTRL+I), selecting the Storage tab, and selecting Application Cache: Notice that you view the status of the Application Cache. In the screen shot above, the status is UNCACHED which means that the files listed in the manifest have not been downloaded and cached yet. The different possible values for the status are included in the HTML5 Offline Web Application standard: UNCACHED – The Application Cache has not been initialized. IDLE – The Application Cache is not currently being updated. CHECKING – The Application Cache is being fetched and checked for updates. DOWNLOADING – The files in the Application Cache are being updated. UPDATEREADY – There is a new version of the Application. OBSOLETE – The contents of the Application Cache are obsolete. Summary In this blog entry, I provided a description of how you can use the HTML5 Offline Web Application feature in the context of an ASP.NET application. I described how this feature is used with the JavaScript Reference Application to store the entire application on a user’s computer. By taking advantage of this new feature of the HTML5 standard, you can improve the performance of your ASP.NET web applications by requiring users of your web application to download your application once and only once. Furthermore, you can enable users to take advantage of your applications anywhere -- regardless of whether or not they are connected to the Internet.

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  • Tkinter on Ubuntu 14.04 seems not to work

    - by empedokles
    I receive following Traceback: Traceback (most recent call last): File "tkinter_basic_frame.py", line 4, in <module> from Tkinter import Tk, Frame, BOTH File "/usr/lib/python2.7/lib-tk/Tkinter.py", line 42, in raise ImportError, str(msg) + ', please install the python-tk package' ImportError: No module named _tkinter, please install the python-tk package This is the demoscript I'm trying to run: #!/usr/bin/python # -*- coding: utf-8 -*- from Tkinter import Tk, Frame, BOTH class Example(Frame): def __init__(self, parent): Frame.__init__(self, parent, background="white") self.parent = parent self.initUI() def initUI(self): self.parent.title("Simple") self.pack(fill=BOTH, expand=1) def main(): root = Tk() root.geometry("250x150+300+300") app = Example(root) root.mainloop() if __name__ == '__main__': main() From my knowledge Tkinter should be included in Python 2.7. Why do I receive the traceback? Doesn't ubuntu contain the standard-python-distribution? This is solved. I had to install it manually in synaptic (got the hint in the meantime from another forum), see here: Wikipedia says: "Tkinter is a Python binding to the Tk GUI toolkit. It is the standard Python interface to the Tk GUI toolkit1 and is Python's de facto standard GUI,2 and is included with the standard Windows and Mac OS X install of Python." - Not good, that it isn't included in Ubuntu as well. Tkinter on Wikipedia

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  • Why does "quickly share --ppa share" abort with a "can't create" error?

    - by desgua
    I can not figure out what I am doing wrong. The package builds ok with quickly package, I could submit it, but I can not update my ppa. Here is what I got: desgua@desguai7:~/quickly/sbk$ quickly share --ppa sbk Get Launchpad Settings Launchpad connection is ok ..........An error has occurred when creating debian packaging ERROR: can't create or update ubuntu package ERROR: share command failed Aborting Edit The name of my ppa was wrong, but even using ppa:desgua/sbk still doesn't work: desgua@desguai7:~/quickly/sbk$ quickly share --ppa ppa:desgua/sbk Get Launchpad Settings Traceback (most recent call last): File "/usr/share/quickly/templates/ubuntu-application/share.py", line 101, in launchpad = launchpadaccess.initialize_lpi() File "/usr/lib/python2.7/dist-packages/quickly/launchpadaccess.py", line 91, in initialize_lpi allow_access_levels=["WRITE_PRIVATE"]) File "/usr/lib/python2.7/dist-packages/launchpadlib/launchpad.py", line 539, in login_with credential_save_failed, version) File "/usr/lib/python2.7/dist-packages/launchpadlib/launchpad.py", line 359, in _authorize_token_and_login service_root, cache, timeout, proxy_info, version) File "/usr/lib/python2.7/dist-packages/launchpadlib/launchpad.py", line 198, in __init__ credentials, service_root, cache, timeout, proxy_info, version) File "/usr/lib/python2.7/dist-packages/lazr/restfulclient/resource.py", line 460, in __init__ self._wadl = self._browser.get_wadl_application(self._root_uri) File "/usr/lib/python2.7/dist-packages/lazr/restfulclient/_browser.py", line 299, in get_wadl_application response, content = self._request(url, media_type=wadl_type) File "/usr/lib/python2.7/dist-packages/lazr/restfulclient/_browser.py", line 242, in _request str(url), method=method, body=data, headers=headers) File "/usr/lib/python2.7/dist-packages/lazr/restfulclient/_browser.py", line 211, in _request_and_retry url, method=method, body=body, headers=headers) File "/usr/lib/python2.7/dist-packages/httplib2/__init__.py", line 1414, in request (response, new_content) = self._request(conn, authority, uri, request_uri, method, body, headers, redirections, cachekey) File "/usr/lib/python2.7/dist-packages/launchpadlib/launchpad.py", line 126, in _request LaunchpadOAuthAwareHttp, self)._request(*args) File "/usr/lib/python2.7/dist-packages/lazr/restfulclient/_browser.py", line 130, in _request redirections, cachekey) File "/usr/lib/python2.7/dist-packages/httplib2/__init__.py", line 1196, in _request (response, content) = self._conn_request(conn, request_uri, method, body, headers) File "/usr/lib/python2.7/dist-packages/httplib2/__init__.py", line 1138, in _conn_request raise ServerNotFoundError("Unable to find the server at %s" % conn.host) httplib2.ServerNotFoundError: Unable to find the server at api.launchpad.net ERROR: share command failed Aborting Any ideas? How could I troubleshot this error?

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