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  • Is it Pythonic to have a class keep track of its instances?

    - by Lightbreeze
    Take the following code snippet class Missile: instances = [] def __init__(self): Missile.instances.append(self) Now take the code: class Hero(): ... def fire(self): Missile() When the hero fires, a missile needs to be created and appended to the main list. Thus the hero object needs to reference the list when it fires. Here are a few solutions, although I'm sure there are others: Make the list a global, Use a class variable (as above), or Have the hero object hold a reference to the list. I didn't post this on gamedev because my question is actually more general: Is the previous code considered okay? Given a situation like this, is there a more Pythonic solution?

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  • Is it safe to lock a static variable in a non-static class?

    - by Dario Solera
    I've got a class that manages a shared resource. Now, since access to the resource depends on many parameters, this class is instantiated and disposed several times during the normal execution of the program. The shared resource does not support concurrency, so some kind of locking is needed. The first thing that came into my mind is having a static instance in the class, and acquire locks on it, like this: // This thing is static! static readonly object MyLock = new object(); // This thing is NOT static! MyResource _resource = ...; public DoSomeWork() { lock(MyLock) { _resource.Access(); } } Does that make sense, or would you use another approach?

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  • how i got the name of the string variable in the strange attempt to debug unknown variable ?

    - by justjoe
    i got several variable. One is variable string, object, and array. $mystring = "hello im input"; $myobject = new userclass; $myarray = array ( 0 = 'zero', 1 = "one"); i want to create a new array with its variable name as key before send it to as function parameter with it's first line use extract function. the multi_array will be like this multi_array = array ( 'mystring' = "hello im input", 'myobject' = new userclass, 'myarray' = array ( 0 = 'zero', 1 = "one") ) i use key to get the name of array and getclass to get the name of object. But how i got the name of the string variable ? function i_do_extract($multi_array) { extract($multi_array); // Do Rest }

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  • How to parse strings representing xml.dom.minidom nodes in python?

    - by Francis Davey
    I have a collection of nodes xml.dom.Node objects created using xml.dom.minidom. I store them (individually) in a database by converting them to a string using the toxml() method of a the Node object. The problem is that I'd sometimes like to be able to convert them back to the appropriate Node object using a parser of some kind. As far as I can see the various libraries shipped with python use Expat which won't parse a string like '' or indeed anything which is not a correct xml string. So, does anyone have any ideas? I realise I could pickle the nodes in some way and then unpickle them, but that feels unpleasant and I'd much rather be storing in a form I can read for maintenance purposes. Surely there is something that will do this?

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  • Using a UIPickerView to make a CoreData Relationship

    - by DVG
    Okay, so I have a fairly simple application set up. I have two different CoreData Entities, Games and Platforms, each have one attribute: name, and they have a one-to-many relationship between them. Platforms are populated on the first launch of the application, and will never change as a result of user input. I'm working on my Add view to let the user add new games to their personal database, and each game should select from a platform. The add view itself is a grouped table view with static custom cells. Tapping the platform cell should advance the user to another view to select the platform. My thought is that UIPickerView seems like a logical choice for the control, since the Platform list is static, but I'm not sure how to use it with CoreData. Even if I construct a fetch request to get the Platform objects and extract the strings out, how do I go about linking the new Game object to the original Platform object?

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  • Parallel EntityFramework

    - by mehanik
    Is it possible to make some work in parallel with entity framework for following example? using (var dbContext = new DB()) { var res = (from c in dbContext.Customers orderby c.Name select new { c.Id, c.Name, c.Role } ).ToDictionary(c => c.Id, c => new Dictionary<string, object> { { "Name",c.Name }, { "Role", c.Role } }); } For exampe what will be changed if I add AsParrallel? using (var dbContext = new DB()) { var res = (from c in dbContext.Customers orderby c.Name select new { c.Id, c.Name, c.Role } ).AsParallel().ToDictionary(c => c.Id, c => new Dictionary<string, object> { { "Name",c.Name }, { "Role", c.Role } }); }

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  • What programming technique / practice done by you was ahead of its time?

    - by Binoj Antony
    I once built a very good web application in ASP (classic) back in 2001 and extensively used XmlHttpRequest object in it. (I was lucky that the clients were only using IE, and only IE supported this object at that time). Then later when people started talking about AJAX in 2005, It felt good to have used something ahead (or early) of its time. Well, maybe this does not qualify to be listed as something done ahead of its time. Which programming technology/technique/practice have you done that was ahead of this time. One story per answer please. The title for this question taken from an opposite question here.

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  • Inheriting from class that inherits from DynamicObject

    - by SeveQ
    Hello there, I'm experimenting with C# 4.0's dynamic object model. I've created an abstract class named "Block" that inherits from DynamicObject. It overrides TryGetMember and TrySetMember. Furthermore I've created a usable class named "Brush" that inherits from "Block". I want it to be usable dynamically. But when I create a dynamic object from it and try to access a runtime bound member, it pelts me with an exception telling me that the member doesn't exist. The overridden TryGetMember or TrySetMember methods of the abstract parent class aren't getting called. Is this behaviour to be expected? Thank you!

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  • wpf c# media player questions

    - by Sankar
    I'm making a media player in wpf using c#. I had 3 questions. 1) I tried making a seeker XAML: <Slider Name="timelineSlider" Margin="40,91,26,0" ValueChanged="SeekToMediaPosition" Height="32" VerticalAlignment="Top" /> Code: private void Element_MediaOpened(object sender, EventArgs e) { timelineSlider.Maximum = ply.NaturalDuration.TimeSpan.TotalMilliseconds; } private void SeekToMediaPosition(object sender, RoutedPropertyChangedEventArgs<double> e) { int SliderValue = (int)timelineSlider.Value; TimeSpan ts = new TimeSpan(SliderValue, SliderValue, SliderValue, SliderValue, SliderValue); ply.Position = ts; } When I run the program, I open the mp3 and play it but the seeker won't move. When I click on the seeker to move it to a certain position, the song stops playing but the seeker moves. What's the problem and how do I fix it? How do I create a volume increase/decrease bar? How can I open several mp3s and queue them up like a playlist? Thank you

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  • Chrome plugin removal

    - by kambamsu
    Hi, I'm writing an NPAPI plugin. In every webpage that the browser goes to, I inject my plugin with an object tag. Something like: <object id="myplugin" type="plugin-mime-type" > In some pages where i dont want it, after injection i remove it by finding the element using the id and doing a document.removeChild. From my logging i found that in firefox and opera, doing this automatically calls the plugin destroy method NPP_Destroy (NPAPI). But in chrome, it doesnt seem to call it. Is there any special way that i should remove a plugin in chrome that i am missing?? Any help would be appreciated. Thanks

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  • SCons: How to use the same builders for multiple variants (release/debug) of a program

    - by OK
    The SCons User Guide tells about the usage of Multiple Construction Environments to build build multiple versions of a single program and gives the following example: opt = Environment(CCFLAGS = '-O2') dbg = Environment(CCFLAGS = '-g') o = opt.Object('foo-opt', 'foo.c') opt.Program(o) d = dbg.Object('foo-dbg', 'foo.c') dbg.Program(d) Instead of manually assigning different names to the objects compiled with different environments, VariantDir() / variant_dir sounds like a better solution... But if I place the Program() builder inside the SConscript: Import('env') env.Program('foo.c') How can I export different environments to the same SConscript file? opt = Environment(CCFLAGS = '-O2') dbg = Environment(CCFLAGS = '-g') SConscript('SConscript', 'opt', variant_dir='release') #'opt' --> 'env'??? SConscript('SConscript', 'dbg', variant_dir='debug') #'dbg' --> 'env'??? Unfortunately the discussion in the SCons Wiki does not bring more insight to this topic. Thanks for your input!

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  • SSIS - How do I see/set the field types in a Recordset?

    - by thursdaysgeek
    I'm looking at an inherited SSIS package, and a stored procedure is sending records to a recordset called USER:NEW_RECORDS. It's of type Object, and the value is System.Object. It is then used for inputting that data to a SQL table. We're getting an error, because it seems that the numeric results of the stored procedure are being put in a DT_WSTR field, and then failing when it is then put into a decimal field in the database. Most of the records are working, but one, which happens to have a longer number of decimal digits, is failing. I want to see exactly what my SSIS recordset field types are, and probably change them, so I can force the data to be truncated properly and copied. Or, perhaps, I'm not even looking at this correctly. The data is put into the recordset using a SQL Task that executes the stored procedure.

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  • can't persist jpa entity in app engine

    - by Bunny Rabbit
    public class Blobx { private String name; private BlobKey blobKey; @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Key id; //getters and setters } public class Userx { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Key id; private String name; @OneToMany private List<Blobx> blobs; //getters and setters } while persiting the above Userx entity object i am encountering java.lang.IllegalStateException: Field "entities.Userx.blobs" contains a persistable object that isnt persistent, but the field doesnt allow cascade-persist!

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  • Rails ActiveResource Associations

    - by brad
    I have some ARes models (see below) that I'm trying to use associations with (which seems to be wholly undocumented and maybe not possible but I thought I'd give it a try) So on my service side, my ActiveRecord object will render something like render :xml => @group.to_xml(:include => :customers) (see generated xml below) The models Group and Customers are HABTM On my ARes side, I'm hoping that it can see the <customers> xml attribute and automatically populate the .customers attribute of that Group object , but the has_many etc methods aren't supported (at least as far as I can tell) So I'm wondering how ARes does it's reflection on the XML to set the attributes of an object. In AR for instance I could create a def customers=(customer_array) and set it myself, but this doesn't seem to work in ARes. One suggestion I found for an "association" is the just have a method def customers Customer.find(:all, :conditions => {:group_id => self.id}) end But this has the disadvantage that it makes a second service call to look up those customers... not cool I'd like my ActiveResource model to see that the customers attribute in the XML and automatically populate my model. Anyone have any experience with this?? # My Services class Customer < ActiveRecord::Base has_and_belongs_to_many :groups end class Group < ActiveRecord::Base has_and_belongs_to_many :customer end # My ActiveResource accessors class Customer < ActiveResource::Base; end class Group < ActiveResource::Base; end # XML from /groups/:id?customers=true <group> <domain>some.domain.com</domain> <id type="integer">266</id> <name>Some Name</name> <customers type="array"> <customer> <active type="boolean">true</active> <id type="integer">1</id> <name>Some Name</name> </customer> <customer> <active type="boolean" nil="true"></active> <id type="integer">306</id> <name>Some Other Name</name> </customer> </customers> </group>

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  • Passing complex objects to javascript via IScriptControl

    - by Jeff Dege
    I'm playing around with a asp.net page that's using the IScriptControl interface to pass data from the code-behind to the custom javascript object running on the browser. I'm passing a number of properties via IScriptControl.GetScriptDescriptors(), and they're all working fine, except for one. That one is a class derived from System.Collections.Generic.Dictionary<. And even that one has been working for me, so long as the elements in the collection were scalars - ints, doubles, and strings. But when I tried to pass a member of a class, it showed up as a null object in the javascript. The class in question is marked [Serializable]. I changed it to a struct, and got the same behavior. It looks as if the serializer used in IScriptControl does a shallow copy. I need a deep copy. Any ideas?

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  • Hibernate advanced select

    - by Marcus
    We want to get a row from a table using Hibernate a la: select max(id) from mytable where date = <date> Then select * from mytable where id = <max_id> We are currently using Hibernate to map mytable to Java domain objects. I know how to load the domain object based on an id. So I could just do #1 using JDBC and then load the domain object using Hibernate the "normal" way. But.. is there a way to do this with one single Hibernate logical query?

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  • SQL Select Permissions

    - by Brandi
    I have a database that I need to connect to and select from. I have an SQL Login, let's call it myusername. When I use the following, no SELECT permission shows up: SELECT * FROM fn_my_permissions ('dbo.mytable', 'OBJECT') GO Several times I tried things like: USE mydatabase GO GRANT SELECT TO myusername GO GRANT SELECT ON DATABASE::mydatabase TO myusername GO GRANT SELECT ON mytable TO myusername GO It says the queries execute successfully, but there is never any difference in the first query. What simple thing am I missing to grant database level select permissions. As a note, I made double sure it was the correct user, correct database, and I have already tried granting table level select permissions. So far I keep getting the error: SELECT permission denied on object 'mytable', database 'mydatabase', schema 'dbo'. Any ideas what I'm missing? Thanks in advance.

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  • Passing a non-iterable to list.extend ()

    - by JS
    Hello, I am creating a public method to allow callers to write values to a device, call it write_vals() for example. Since these values will by typed live, I would like to simplify the user's life by allowing them type in either a list or a single value, depending on how many values they need to write. For example: write_to_device([1,2,3]) or write_to_device(1) My function would like to work with a flat list, so I tried to be clever and code something like this: input_list = [] input_list.extend( input_val ) This works swimmingly when the user inputs a list, but fails miserably when the user inputs a single integer: TypeError: 'int' object is not iterable Using list.append() would create a nested list when a list was passed in, which would be an additional hassle to flatten. Checking the type of the object passed in seems clumsy and non-pythonic and wishing that list.extend() would accept non-iterables has gotten me nowhere. So has trying a variety of other coding methods. Suggestions (coding-related only, please) would be greatly appreciated.

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  • ASP.net Error in Design Mode

    - by stringo0
    I just switched to VS 2010, and upgraded a previous project. I'm getting the following error on a page in design mode for 2 controls: Error Creating Control - ObjectName Object reference not set to an instance of an object. One of them is a simple label, and the other is a ajax update panel. Other pages look fine. When I build and test the app, the page renders fine in the browser and functions fine - the label functions as expected and the content in the update panel works as expected. Any ideas why I'm getting this error? I tried some of the google results to no avail. It'd be great to get this out of the way. Thanks!

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  • Automate Testing on future only items business rules

    - by Titan
    I currently have a business object with a validation business rule, which is it can only be created for the future, tomorrow onwards, and I cannot create new items for today. I have a process, which runs the non-future business objects through some steps.. Because I have to set things up today, and test tomorrow, and when it fails, I can only create a new object tomorrow and test the following day. Are there any easy ways to automate this process in any testing frameworks? I think our testers are using the visual studio 2010 test manager. How do you guys manage situations like this? Cheers

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  • Binding list of objects to WPF ListView

    - by Dave Colwell
    Hi all, I have a list of objects which i want to bind to a ListView control in my WPF application. The Objects have a DataTemplate already, so no need to define that. The list of objects is a property in the codebehind file in the format list<object> When i add one object programatically, it appears fine. But when i try to bind the ItemSource of the ListBox to the list of objects, nothing shows up. I am using the following binding: ItemsSource="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}, Path=Portfolios}" where the name of the property i am trying to bind to is Portfolios and exists on the parent window

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  • Date exception when trying to use date method

    - by Simon Andi
    Hi, I have defined a object model where one of the array elements is a string public static String[] columnNames6 = {"Total Shares", "Total Calls", "Call Strike", "Call Premium", "Call Expiry" }; public static Object[][] data6 = { { new Double(0), new Double(0), new Double(0), new Double(0),"dd/mm/yyyy"}, }; I then use the following code to get the date so that I can use the data method but having no joy - Can someone please tell me why it is throwing an exception after I do this String ExpiryDate = (String)GV.data6[0][4]; System.out.println("DATE STRING IS: " + ExpiryDate); Date EndOptionDate = new Date(ExpiryDate); // SOMETHING WRONG HERE even though it compiles okay //Get Todays's Date Date TodaysDate = new Date(); //Calculate Days Option Expiry long DaysDifference = EndOptionDate.getTime() - TodaysDate.getTime(); Would really appreciate some help as really stuck not sure how I should code the line in bold - new to java, so please excuses my lack of knowledge looked at tutorials can't seem to move forward. Thanks Simon

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  • Storing simulation results in a persistent manner for Python?

    - by Az
    Background: I'm running multiple simuations on a set of data. For each session, I'm allocating projects to students. The difference between each session is that I'm randomising the order of the students such that all the students get a shot at being assigned a project they want. I was writing out some of the allocations in a spreadsheet (i.e. Excel) and it basically looked like this (tiny snapshot, actual table extends to a few thousand sessions, roughly 100 students). | | Session 1 | Session 2 | Session 3 | |----------|-----------|-----------|-----------| |Stu1 |Proj_AA |Proj_AB |Proj_AB | |----------|-----------|-----------|-----------| |Stu2 |Proj_AB |Proj_AA |Proj_AC | |----------|-----------|-----------|-----------| |Stu3 |Proj_AC |Proj_AC |Proj_AA | |----------|-----------|-----------|-----------| Now, the code that deals with the allocation currently stores a session in an object. The next time the allocation is run, the object is over-written. Thus what I'd really like to do is to store all the allocation results. This is important since I later need to derive from the data, information such as: which project Stu1 got assigned to the most or perhaps how popular Proj_AC was (how many times it was assigned / number of sessions). Question(s): What methods can I possibly use to basically store such session information persistently? Basically, each session output needs to add itself to the repository after ending and before beginning the next allocation cycle. One solution that was suggested by a friend was mapping these results to a relational database using SQLAlchemy. I kind of like the idea since this does give me an opportunity to delve into databases. Now the database structure I was recommended was: |----------|-----------|-----------| |Session |Student |Project | |----------|-----------|-----------| |1 |Stu1 |Proj_AA | |----------|-----------|-----------| |1 |Stu2 |Proj_AB | |----------|-----------|-----------| |1 |Stu3 |Proj_AC | |----------|-----------|-----------| |2 |Stu1 |Proj_AB | |----------|-----------|-----------| |2 |Stu2 |Proj_AA | |----------|-----------|-----------| |2 |Stu3 |Proj_AC | |----------|-----------|-----------| |3 |Stu1 |Proj_AB | |----------|-----------|-----------| |3 |Stu2 |Proj_AC | |----------|-----------|-----------| |3 |Stu3 |Proj_AA | |----------|-----------|-----------| Here, it was suggested that I make the Session and Student columns a composite key. That way I can access a specific record for a particular student for a particular session. Or I can merely get the entire allocation run for a particular session. Questions: Is the idea a good one? How does one implement and query a composite key using SQLAlchemy? What happens to the database if a particular student is not assigned a project (happens if all projects that he wants are taken)? In the code, if a student is not assigned a project, instead of a proj_id he simply gets None for that field/object. I apologise for asking multiple questions but since these are closely-related, I thought I'd ask them in the same space.

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