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  • Is it inefficient to access a python class member container in a loop statement?

    - by Dave
    Hi there. I'm trying to adopt some best practices to keep my python code efficient. I've heard that accessing a member variable inside of a loop can incur a dictionary lookup for every iteration of the loop, so I cache these in local variables to use inside the loop. My question is about the loop statement itself... if I have the following class: class A(object): def init(self) self.myList = [ 'a','b','c', 'd', 'e' ] Does the following code in a member function incur one, or one-per-loop-iteration (5) dictionary lookups? for letter in self.myList: print letter IE, should I adopt the following pattern, if I am concerned about efficiency... localList = self.myList for letter in localList: print letter or is that actually LESS efficient due to the local variable assign? Note, I am aware that early optimization is a dangerous pitfall if I'm concerned about the overall efficiency of code development. Here I am specifically asking about the efficiency of the code, not the coding. Thanks in advance! D

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  • iPhone UIImage number recognition

    - by Skeep
    Hi All, I have a small UIImage (jpg) with a single typed number. I want to be able to read the number with some kind of pattern recognition. I'm really not sure where to start, so any help would be appreciated. my initial idea was to compare this image with other images. For instance compare the image with that of a 1,2,3, etc until a match was found. That just seems slow and cumbersome and wondered if there was a better way to do it? Thanks

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  • Irregular layout ItemsControl

    - by firoso
    I have a strange layout for an ItemsControl. I have a 4x6 grid with the following pattern: 1 2 3 4 13 14 15 16 5 6 7 8 17 18 19 20 9 10 11 12 21 22 23 24 Is there an easy way to do this? should I be using 6 Items Controls and take "sections" of my list? is there a good way to do this? What about notification? It's important to note that I may, or may not, have all 24 entries present, but the layout needs to be maintained (think of it like filled slots on a bingo card or something)

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  • What are the hibernate annotations used to persist a Map with an enumerated type as a key?

    - by Jason Novak
    I am having trouble getting the right hibernate annotations to use on a Map with an enumerated class as a key. Here is a simplified (and extremely contrived) example. public class Thing { public String id; public Letter startLetter; public Map<Letter,Double> letterCounts = new HashMap<Letter, Double>(); } public enum Letter { A, B, C, D } Here are my current annotations on Thing @Entity public class Thing { @Id public String id; @Enumerated(EnumType.STRING) public Letter startLetter; @CollectionOfElements @JoinTable(name = "Thing_letterFrequencies", joinColumns = @JoinColumn(name = "thingId")) @MapKey(columns = @Column(name = "letter", nullable = false)) @Column(name = "count") public Map<Letter,Double> letterCounts = new HashMap<Letter, Double>(); } Hibernate generates the following DDL to create the tables for my MySql database create table Thing (id varchar(255) not null, startLetter varchar(255), primary key (id)) type=InnoDB; create table Thing_letterFrequencies (thingId varchar(255) not null, count double precision, letter tinyblob not null, primary key (thingId, letter)) type=InnoDB; Notice that hibernate tries to define letter (my map key) as a tinyblob, however it defines startLetter as a varchar(255) even though both are of the enumerated type Letter. When I try to create the tables I see the following error BLOB/TEXT column 'letter' used in key specification without a key length I googled this error and it appears that MySql has issues when you try to make a tinyblob column part of a primary key, which is what hibernate needs to do with the Thing_letterFrequencies table. So I would rather have letter mapped to a varchar(255) the way startLetter is. Unfortunately, I've been fussing with the MapKey annotation for a while now and haven't been able to make this work. I've also tried @MapKeyManyToMany(targetEntity=Product.class) without success. Can anyone tell me what are the correct annotations for my letterCounts map so that hibernate will treat the letterCounts map key the same way it does startLetter?

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  • MVC - Sanitizing data, where?

    - by dierre
    I'm using CakePHP but it's a question about the MVC pattern. I have in my form the input-text for the tags (separated by commas). To add the tags I've created a Tag model method that basically check if the tag exists and then add the new tag or just a new unit in the tag counter (the Tag model has these fields: id, name, slug, count). In the controller I explode the tags field and pass one tag at a time. The question is: where do I sanitize data? In the controller or in the model method? I think it should be in the controller because that's where I explode but in term of reusability I think I should sanitize data in the model. What do you think?

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  • Google Gears hangs when capturing (unmanaged resource store)

    - by Gus
    Our code was written based on the example from Google Gears' own docs. We're using an unmanaged resource store. So we declare the files in an array, create the store, and capture all the files. Trouble is, the capturing process hangs. It always hangs on a random file (no discernible pattern has emerged), and when you reload the page, it always successfully captures. We're capturing 48 files. It seems to have nothing to do with the files themselves, as it hangs on every file type. I've seen it hang on the 6th file or the 47th. Windows and Mac. FF, IE, and Safari. We are not using a WorkerPool, and I'm thinking this may be necessary. Any other ideas why it would hang?

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  • Should I always release self for failed init methods?

    - by leo
    Should I always release self when there is a failure inside init, or should I only do so if I have initialized instance variables first? To put it another way, is this pattern valid? Is there a time when I shouldn't release self inside an init method, or should I assume that if the control flow enters init, self has at least a retain count of 1? - (id)init { if ((self = [super init]) == nil) { [self release]; return nil; } //do some init stuff if (somethingFailed) { [self release]; return nil; } return self; }

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  • Scala match/compare enumerations

    - by williamstw
    I have an enumeration that I want to use in pattern matches in an actor. I'm not getting what i'd expect and, now, I'm suspecting I'm missing something simple. My enumeration, object Ops extends Enumeration { val Create = Value("create") val Delete = Value("delete") } Then, I create an Ops from a String: val op = Ops.valueOf("create") Inside my match, I have: case (Ops.Create, ...) But Ops.Create doesn't seem to equal ops.valueOf("create") The former is just an atom 'create' and the later is Some(create) Hopefully, this is enough info for someone to tell me what I'm missing... Thanks

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  • Dynamically adding Views in Silverlight & MVVM

    - by dvox
    Hi all, I am starting to re-write my whole silverlight business application in the MVVM pattern; My first stop-point is this: I have a page (View1) with corresponding ViewModel1 (with a property 'IEnumerable AllData'); Now, within this View, I want to have i.e. a tree-view control, in which one node will be populated with another View2; My question is: 1. How to do it? - I can't loop through the AllData property since it is asynchronously loaded... - thus I don't know the number of View2s' to insert - I don't know how to do it from ViewModel1 :( Will I need ViewModel2 with property 'MyDataEntity CurrentData'? or I can bind to AllData property from ViewModel1 Can you help me out? Thanks

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  • django-haystack urlpatterns include('haystack.urls') where does it lead to?

    - by Eugene
    I've recently begun to learn/install django/haystack/solr. Following the tutorial given in haystack site, I have urlpatterns = pattern('', r'^search/', include('haystack.urls')) I found haystack installed in /usr/local/lib/python2.6/dist-packages/haystack and located urls.py there. It has urlpatterns=patterns('haystack.views', url(r'^$', SearchView(), name='haystack_search'),) I thought the second argument of url() should be callable object. I looked at the views.py and SearchView is a class. What is going on here? What's get called eventually?

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  • WPF MVVM: How do ViewModels communicate with each other?

    - by Dev1
    I have a View which has 2 sub views on it and a ViewModel is assigned to each view: ViewA - ViewModelA { ViewB - ViewModelB ViewC - ViewModelC } ViewB has a text box and ViewC has a combobox, both of which i need access from ViewModelA. Not the GUI control itself, but the bound value i.e. .Text of the textbox and .SelectedItem of the ComboBox. Currently i just have ViewModelB and ViewModelC as properties on ViewModelA but it feels wrong. What's the standard way for view models to communicate with each other without breaking the MVVM pattern? I'm completely new to WPF/MVVM.

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  • interview questions for a test lead

    - by PJ
    Maybe this question has been asked although I didn't find the answer. I am going to attend an interview for a test lead. can you tell me the pattern of questions I will have to face other than the normal question that I was facing previously like What is Software testing? What is Bug life cycle? or Grilling me on my project experience. Also I wnat to know when they are going to hire me for a test lead what would they want to see as an extra add ons?

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  • Help me understand the code snippet in c#

    - by Benny
    I am reading this blog: Pipes and filters pattern I am confused by this code snippet: public class Pipeline<T> { private readonly List<IOperation<T>> operations = new List<IOperation<T>>(); public Pipeline<T> Register(IOperation<T> operation) { operations.Add(operation); return this; } public void Execute() { IEnumerable<T> current = new List<T>(); foreach (IOperation<T> operation in operations) { current = operation.Execute(current); } IEnumerator<T> enumerator = current.GetEnumerator(); while (enumerator.MoveNext()); } } what is the purpose of this statement: while (enumerator.MoveNext());? seems this code is a noop.

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  • php regex to split invoice line item description

    - by user1053700
    I am attempting to split strings like the following: An item (Item A) which may contain 89798 numbers and letters @ $550.00 4 of Item B @ $420.00 476584 of Item C, with a larger quantity and different currency symbol @ £420.00 into: array( 0 => 1 1 => "some item which may contain 89798 numbers and letters" 2 => $550.00 ); does that make sense? I am looking for a regex pattern which will split the quantity, description, and price (including symbol). the strings will always be: qty x description @ price+symbol so i assume the regex would be something like: `(match a number and only a number) x (get description letters and numbers before the @ symbol) @ (match the currency symbol and price)` How should I approach this?

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  • How to handle recursive parent/child problems like this?

    - by lsdude
    In web dev I come across these problems a lot. For example, we have a giant list of URLs that are in this format: /businesses /businesses/food /businesses/food/wendys /businesses/food/wendys/chili /businesses/food/wendys/fries /businesses/food/wendys/chicken-nuggets /businesses/pharmacy/cvs /businesses/pharmacy/cvs/toothpaste /businesses/pharmacy/cvs/toothpaste/brand ... and then we need to output each one, where the parent category is in h1 tags, the child is in h2 tags, and the children of that are in h3 tags. I can handle this but I feel my code is messy. I'm sure there is a design pattern I can use? Langs are ruby/php usually. how would you handle this?

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  • What elegant method callback design should be used ?

    - by ereOn
    Hi, I'm surprised this question wasn't asked before on SO (well, at least I couldn't find it). Have you ever designed a method-callback pattern (something like a "pointer" to a class method) in C++ and, if so, how did you do it ? I know a method is just a regular function with some hidden this parameter to serve as a context and I have a pretty simple design in mind. However, since things are often more complex than they seem to, I wonder how our C++ gurus would implement this, preferably in an elegant and standard way. All suggestions are welcome !

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  • What difference does it make to use several script blocks on a web page?

    - by Jan Aagaard
    What difference does it make to use more than one script block on a web page? I have pasted in the standard code for including Google Analytics as an example, and I have seen the same pattern used in other places. Why is this code separated into two separate script blocks instead of just using a single one? <script type="text/javascript"> var gaJsHost = (("https:" == document.location.protocol) ? "https://ssl." : "http://www."); document.write(unescape("%3Cscript src='" + gaJsHost + "google-analytics.com/ga.js' type='text/javascript'%3E%3C/script%3E")); </script> <script type="text/javascript"> try{ var pageTracker = _gat._getTracker("UA-xxxxxx-x"); pageTracker._trackPageview(); } catch(err) {} </script>

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  • When should I use adorners?

    - by Francesco
    Hi all! WPF is great because there are many things to achieve own goals. By example, for what I understand, adorners can add some controls to a UI element, but I think that the same behavior can be achieved through a custom control that contains the additional element. So, my question is: when should I prefer adorners to a more complex (but I think, more flexible) custom control? Please consider that I'm extensively using MVVM pattern and I would like to bind commands to the additional element. Particularly, I'm designing a diagram designer application and I would like to add connection points to my shapes. Thank you

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  • Using Remote Web Page to Initialize iPhone App

    - by Chris_K
    My iPhone app relies on a vendor's XML feed to provide data. But that feed is not locked down. The vendor could change the format of the XML at any time, although so far they've promised not to. Since I might want to tell my app to use a different URL for its data source, I'd like to set up a single "Command Central" Web page, on my own server, to direct the app to the correct data source. In other words, each time my app starts, in the background and unseen by the user, it would visit "http://www.myserver.com/iphoneapp_data_sources.xml" to retrieve the URL for retrieving data from my vendor. That way, if my vendor suddenly changes the exact URL or the XML feed that the app needs, I can update that Web page and ensure that all installations of the app are using the correct XML feed. Does anyone have any advice or examples showing this kind of approach? It seems as if this must be a common problem, but so far I haven't found a well-established design pattern that fits it.

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  • Castle Windsor Weak Typed Factory

    - by JeffN825
    In a very very limited number of scenarios, I need to go from an unknown Type (at compile time) to an instance of the object registered for that type. For the most part, I use typed factories and I know the type I want to resolve at compile time...so I inject a Func<IMyType> into a constructor ...but in these limited number of scenarios, in order to avoid a direct call to the container (and thus having to reference Windsor from the library, which is an anti-pattern I'd like to avoid), I need to inject a Func<Type,object>...which I want to internally container.Resolve(type) for the Type parameter of the Func. Does anyone have some suggestions on the easiest/most straightforward way of setting this up? I tried the following, but with this setup, I end up bypassing the regular TypedFactoryFacility altogether which is definitely not what I want: Kernel.Register(Component.For(typeof (Func<Type, object>)).LifeStyle.Singleton.UsingFactoryMethod( (kernel, componentModel, creationContext) => kernel.Resolve(/* not sure what to put here... */))); Thanks in advance for any assistance.

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  • What's the fastest way to compare two objects in PHP?

    - by johnnietheblack
    Let's say I have an object - a User object in this case - and I'd like to be able to track changes to with a separate class. The User object should not have to change it's behavior in any way for this to happen. Therefore, my separate class creates a "clean" copy of it, stores it somewhere locally, and then later can compare the User object to the original version to see if anything changed during its lifespan. Is there a function, a pattern, or anything that can quickly compare the two versions of the User object? Option 1 Maybe I could serialize each version, and directly compare, or hash them and compare? Option 2 Maybe I should simply create a ReflectionClass, run through each of the properties of the class and see if the two versions have the same property values? Option 3 Maybe there is a simple native function like objects_are_equal($object1,$object2);? What's the fastest way to do this?

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  • Optimizing NSNumber numberWithInt:

    - by Riviera
    I am profiling an iPhone app and I noticed a strange pattern. In a certain block of code that's called quite frequently... [item setQuadrant:[NSNumber numberWithInt:a]]; [item setIndex:[NSNumber numberWithInt:b]]; [item setTimestamp:[NSNumber numberWithInt:c]]; [item setState:[NSNumber numberWithInt:d]]; [item setCompletionPercentage:[NSNumber numberWithInt:e]]; [item setId_:[NSNumber numberWithInt:f]]; ...the first call to [NSNumber numberWithInt:] takes an inordinate amount of time, in the order of 10-15x that of the remaining calls. I've verified that the results are consistent if I shuffle the lines (the first line is always the slow one, by the same ratio). Is there something going on that I'm not aware of? Perhaps this happens because this block is inside a try/catch?

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  • How can an Android Service know that its not bound to any Activities

    - by tunneling
    I have an Android Service that I would like to keep running even after the last Activity has been popped off the stack, or the User has chosen to do something else. Essentially the Service is listening for changes on a remote server, and I would like to generate a Notification if and only if an Activity from the app isn't running(or visible). In other words, I don't want the Notifications to occur while the User is directly interacting with the app. In the case where the User is directly interacting with the app, the Service will notify the Activity and update appropriate UI elements based on the changes. I plan to implement this through the Observer pattern. How can the Service know if none of apps Activities are bound to it? Thanks, J

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  • Why null reference exception in SetMolePublicInstance?

    - by OldGrantonian
    I get a "null reference" exception in the following line: MoleRuntime.SetMolePublicInstance(stub, receiverType, objReceiver, name, null); The program builds and compiles correctly. There are no complaints about any of the parameters to the method. Here's the specification of SetMolePublicInstance, from the object browser: SetMolePublicInstance(System.Delegate _stub, System.Type receiverType, object _receiver, string name, params System.Type[] parameterTypes) Here are the parameter values for "Locals": + stub {Method = {System.String <StaticMethodUnitTestWithDeq>b__0()}} System.Func<string> + receiverType {Name = "OrigValue" FullName = "OrigValueP.OrigValue"} System.Type {System.RuntimeType} objReceiver {OrigValueP.OrigValue} object {OrigValueP.OrigValue} name "TestString" string parameterTypes null object[] I know that TestString() takes no parameters and returns string, so as a starter to try to get things working, I specified "null" for the final parameter to SetMolePublicInstance. As already mentioned, this compiles OK. Here's the stack trace: Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object. at Microsoft.ExtendedReflection.Collections.Indexable.ConvertAllToArray[TInput,TOutput](TInput[] array, Converter`2 converter) at Microsoft.Moles.Framework.Moles.MoleRuntime.SetMole(Delegate _stub, Type receiverType, Object _receiver, String name, MoleBindingFlags flags, Type[] parameterTypes) at Microsoft.Moles.Framework.Moles.MoleRuntime.SetMolePublicInstance(Delegate _stub, Type receiverType, Object _receiver, String name, Type[] parameterTypes) at DeqP.Deq.Replace[T](Func`1 stub, Type receiverType, Object objReceiver, String name) in C:\0VisProjects\DecP_04\DecP\DeqC.cs:line 38 at DeqPTest.DecCTest.StaticMethodUnitTestWithDeq() in C:\0VisProjects\DecP_04\DecPTest\DeqCTest.cs:line 28 at Starter.Start.Main(String[] args) in C:\0VisProjects\DecP_04\Starter\Starter.cs:line 14 Press any key to continue . . . To avoid the null parameter, I changed the final "null" to "parameterTypes" as in the following line: MoleRuntime.SetMolePublicInstance(stub, receiverType, objReceiver, name, parameterTypes); I then tried each of the following (before the line): int[] parameterTypes = null; // if this is null, I don't think the type will matter int[] parameterTypes = new int[0]; object[] parameterTypes = new object[0]; // this would allow for various parameter types All three attempts produce a red squiggly line under the entire line for SetMolePublicInstance Mouseover showed the following message: The best overloaded method match for 'Microsoft.Moles.Framework.Moles.MoleRuntime.SetMolePublicInstance(System.Delegate, System.Type, object, string, params System.Type[])' has some invalid arguments. I'm assuming that the first four arguments are OK, and that the problem is with the params array.

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  • What is the purpose of this delegate usage?

    - by Kev
    Whilst poking around some code in .NET Reflector in an app I don't have the source code for I found this: if (DeleteDisks) { using (List<XenRef<VDI>>.Enumerator enumerator3 = list.GetEnumerator()) { MethodInvoker invoker2 = null; XenRef<VDI> vdiRef; while (enumerator3.MoveNext()) { vdiRef = enumerator3.Current; if (invoker2 == null) { // // Why do this? // invoker2 = delegate { VDI.destroy(session, vdiRef.opaque_ref); }; } bestEffort(ref caught, invoker2); } } } if (caught != null) { throw caught; } private static void bestEffort(ref Exception caught, MethodInvoker func) { try { func(); } catch (Exception exception) { log.Error(exception, exception); if (caught == null) { caught = exception; } } } Why not call VDI.destroy() directly. Is this just a way of wrapping the same pattern of try { do something } catch { log error } if it's used a lot?

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