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• Possible to capture the returned value from a Python list comprehension for use a condition?

  - by Joe

  I want to construct a value in a list comprehension, but also filter on that value. For example: [expensive_function(x) for x in generator where expensive_function(x) < 5] I want to avoid calling expensive_function twice per iteration. The generator may return an infinite series, and list comprehensions aren't lazily evaluated. So this wouldn't work: [y in [expensive_function(x) for x in generator where expensive_function(x)] where y < 5] I could write this another way, but it feels right for a list comprehension and I'm sure this is a common usage pattern (possible or not!).

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• Should I bundle C libraries with my Python application?

  - by oceanhug

  If I have a Python package that depends on some C libraries (like say the Gnu Scientific Library (GSL) for numerical computations), is it a good idea to bundle the library with my code? I'd like to make my package as easy to install as possible for users and I don't want them to have to download C libraries by hand and supply include-paths. Also I could always ensure that the version of the library that I ship is compatible with my code. However, is it possible that there are clashes if the user has the library installed already, or ar there any other reasons why I shouldn't do this? I know that I can make it easier for users by just providing a binary distribution, but I'd like to avoid having to maintain binary distributions for all possible OSs. So, I'd like to stick to a source distribution, but for the user (who proudly owns a C compiler) installation should be as easy as python setup.py install.

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• How to sanely read and dump structs to disk when some fields are pointers?

  - by bp

  Hello, I'm writing a FUSE plugin in C. I'm keeping track of data structures in the filesystem through structs like: typedef struct { block_number_t inode; filename_t filename; //char[SOME_SIZE] some_other_field_t other_field; } fs_directory_table_item_t; Obviously, I have to read (write) these structs from (to) disk at some point. I could treat the struct as a sequence of bytes and do something like this: read(disk_fd, directory_table_item, sizeof(fs_directory_table_item_t)); ...except that cannot possibly work as filename is actually a pointer to the char array. I'd really like to avoid having to write code like: read(disk_df, *directory_table_item.inode, sizeof(block_number_t)); read(disk_df, directory_table_item.filename, sizeof(filename_t)); read(disk_df, *directory_table_item.other_field, sizeof(some_other_field_t)); ...for each struct in the code, because I'd have to replicate code and changes in no less than three different places (definition, reading, writing). Any DRYer but still maintainable ideas?

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• sqlplus remove \r \n \t from spool

  - by Tom

  Hi all, Is there any sql*plus command to remove \r \n and\t from the result set that's going out to the spool file? That is, "trim" every record? We've used set trim on in the past, but it doesn't seem to bue what we need right now. I'm trying to avoid calling oracle's translate, chr functions in the sql query. For example, If my query returns this |DATA| |\n \t\t\t\t\t thisistheactualdata \t\t\t\t\t\t\n| I'd like to keep this |DATA| |thisistheactualdata| Thanks in advance.

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• Heavy use of templates for mobile platforms

  - by Chris P. Bacon

  I've been flicking through the book Modern C++ Design by Andrei Alexandrescu and it seems interesting stuff. However it makes very extensive use of templates and I would like to find out if this should be avoided if using C++ for mobile platform development (Brew MP, WebOS, iOS etc.) due to size considerations. In Symbian OS C++ the standard use of templates is discouraged, the Symbian OS itself uses them but using an idiom known as thin templates where the underlying implementation is done in a C style using void* pointers with a thin template layered on top of this to achieve type safety. The reason they use this idiom as opposed to regular use of templates is specifically to avoid code bloating. So what are opinions (or facts) on the use of templates when developing applications for mobile platforms.

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• <Tabcontrol and Canvas

  - by prajor

  Hello, I have following situation <stackpanel > <ViewBox height=25/ > <tabcontrol> <tabitem> <Canvas /> </tabitem> </tabcontrol> </stackpanel> Q1. I want stackpanel to fill the screen, tabcontrol to fill the remain portion after viewbox. How do I do that ? How do I avoid the tabcontrol shrinking based on the size of tab items. Q2. I want the canvas restricted to the tabitem size. Currently I put anything in the canvas and scorll it goes beyond the tab item. Any idea how to control this.

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• How to make WPF app work as a child process in Citrix

  - by RichardOD

  I am working on a 3rd party application that allows plugins to be written in .NET 1.1. I have decided I would like to write my plugin in a seperate process that is called from the .NET 1.1 application (achieved using Process.Start). This is fine- I create a new process that is a WPF app. When I launch this through MSTSC everything works as expected, however when I run the app through Citrix, the WPF child app fails to render correctly, and the mouse position starts going crazy- the child process window is basically not usable. Is there a way to avoid this happening? If I create a seperate WPF application and deploy this through Citrix everything works fine. If I create a child Windows forms app in .NET 3.5, that also works fine.

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• How to set a filter for an estimated maximum price

  - by David

  I cannot figure out how to set an estimated maximum price for a collection of records. What I want to avoid is to simply use SQL MAX, because maybe there are records with exorbitant prices. For example, in the "computers-hardware" category of OLX (http://www.olx.com/computers-hardware-cat-240) the filter for maximum price is estimately set to $1400, but sorting by price, the first items are above $10000 Maybe they calculated the average and then estimated some maximum price... what do you think? And what about the stepping? How would you calculate it?

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• How can I request local pages in the background of an ASP.NET MVC app?

  - by flipdoubt

  My ASP.NET MVC app needs to run a set of tasks at startup and in the background at a regular interval. I have implemented each task as a controller action and listed the app-relative path to the action in the database. I implemented a TaskRunner process that gets the urls from the database and requests each one at a regular interval using WebRequest.Create, but this throws a UriFormatException. I cannot use this answer or any code that plucks values from HttpContext.Current.Request without getting an HttpException with the message "Request is not available in this context". The Request object is not available because my code uses System.Threading.Timer to do background processing, as recommended here. Here are my questions: Is there really no way to make local web requests within an ASP.NET web app? Is there really no way to dynamically ascertain the root path to the web app even using static dependencies in ASP.NET? I was trying to avoid storing the app's root path in the database (as FogBugz does with its "Maintenance Path"), but is this best option?

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• Creating a unique key based on file content in python

  - by Cawas

  I got many, many files to be uploaded to the server, and I just want a way to avoid duplicates. Thus, generating a unique and small key value from a big string seemed something that a checksum was intended to do, and hashing seemed like the evolution of that. So I was going to use hash md5 to do this. But then I read somewhere that "MD5 are not meant to be unique keys" and I thought that's really weird. What's the right way of doing this? edit: by the way, I took two sources to get to the following, which is how I'm currently doing it and it's working just fine, with Python 2.5: import hashlib def md5_from_file (fileName, block_size=2**14): md5 = hashlib.md5() f = open(fileName) while True: data = f.read(block_size) if not data: break md5.update(data) f.close() return md5.hexdigest()

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• Is there such a thing as a converter from php to html?

  - by 0plus1

  Don't think that I'm mad, I understand how php works! That being said. I develop personal website and I usually take advantage of php to avoid repetion during the development phase nothing truly dynamic, only includes for the menus, a couple of foreach and the likes. When the development phase ends I need to give the website in html files to the client. Is there a tool (crawler?) that can do this for me instead of visiting each page and saving the interpreted html?

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• Tool for checking source for dependencies on specific Java versions

  - by Gregor

  Is there a quick way (e.g. tool) to detect, from the source (or maybe even from compiled classes), which parts of an application call Java API methods that are only implemented in a specific Java version? (e.g. which parts of my app are Java6-specific) I don't necessarily want to hop through all ClassMismatchErrors and avoid the trial-and-error-method. Let's say I only want to document which parts of an application won't work if they were writte for, e.g., Java6 and I want to run it in a version 5 JDK. Is there something like this? Google did not help this time, nor did I find any solution here (a rare case indeed:)

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• What to keep in mind when creating your own custom web services API?

  - by John Conde

  I have created a website which allows users to sign up for, and use, an online service. To help promote the website we will be have resellers who will be offering their own branded services through us. The initial plan is to allow resellers to place registration, login, and lost password forms on their own website and use an API created by us to handle these requests. I have begun outlining how I expect the API to work (and starting documenting it as well) and I want to make sure I get it right, or as close to right, as I can from the beginning as I know once you have declared a public API you want to avoid changing that API at all costs. So far I have decided: To have the user pass their account credentials with each request To require SSL for all requests What else should I be keeping in mind?

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• Why is my onSharedPreferenceChangeListener being called multiple times when I change a pref.

  - by brockoli

  I've written an app with 3 tabs. Each tab has the same list view with different data sources. I have setup SharedPreferences in the tabhost activity, but I put my onSharedPreferenceChangeListener method in my listactivity. When I change a preference, my listener gets called and it updates my database. This is all working. However, if I change the data in tab 1, it calls my listener once. If I change the data for tab 2 it calls it twice and if I change the data in tab 3 it calls it three times. Any idea why it works this way? I guess I could setup my shared prefs in my listactivity and that might avoid the issue, but I'm curious why my listener is called multiple times if it's in a different tab. brockoli

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• AS3: creating a class with multiple and optional parameters?

  - by redconservatory

  I'm creating a slideshow where each slide can have: - a video or a still - 1 audio track or many (up to 3) - 1 button or many (up to 3) I was thinking that each slide can be it's own object, and then I would pass the video, audio, buttons, etc., into it as parameters: package { import flash.media.Video; public class Section { public function Section (video:Video, still:myPhotoClass, audiotrack:Sound, button:myButtonClass) { // can have video OR a still // can have 1 audio track or several // can have 1 button or more } } I'm not sure how to go about approaching this since there can be multiples of certain items (audio, buttons) and also two items are sort-of-optional in the sense that there can be ONE or the OTHER (video/still). For example, is this something that I should just avoid passing as parameters altogether, using a different approach (getters/setters, maybe)?

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• Why do I get CA1811 when I call a private method from a public method in C++/CLI?

  - by brickner

  I've recently upgraded my project from Visual Studio 2008 to Visual Studio 2010. By enabling Code Analysis and building on Release, I'm getting warning CA1811: Avoid uncalled private code. I've managed to reduce the code to this: .h file: public ref class Foo { public: virtual System::String^ ToString() override; private: static System::String^ Bar(); }; .cpp file: String^ Foo::ToString() { return Bar(); } String^ Foo::Bar() { return "abc"; } The warning I get: CA1811 : Microsoft.Performance : 'Foo::Bar(void)' appears to have no upstream public or protected callers. It doesn't matter if Bar() is static or not. I've tried to reproduce it in C# but I can't. I can only reproduce it in C++/CLI. Why do I get this warning? Is this a Visual Studio 2010 bug?

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• Correct (pretty) window redraw during the creation

  - by Coder

  Does anyone know what is a correct way to redraw window during lengthy initialization operations? Say I have HWND with NULL brush, and it does some not so quick child window initialization (Window initialization is not so quick on Vista and 7, especially on netbooks, even with threaded app). With this config window stays black for half a second on slower laptops. But if I supply window color brush, it seems that there are some sort of child controls or something that draws black squares on top of it, which also seems ugly. Even though the controls are created without WS_VISIBLE initially. Oh, the window has the WS_EX_COMPOSITED style, which should do the double buffering to avoid flicker. But it still behaves ugly. Are there any other tricks I've forgotten, missed?

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• Retain cycle on `self` with blocks

  - by Jonathan Sterling

  I'm afraid this question is pretty basic, but I think it's relevant to a lot of Objective-C programmers who are getting into blocks. What I've heard is that since blocks capture local variables referenced within them as const copies, using self within a block can result in a retain cycle, should that block be copied. So, we are supposed to use __block to force the block to deal directly with self instead of having it copied. __block typeof(self) bself = self; [someObject messageWithBlock:^{ [bself doSomething]; }]; instead of just [someObject messageWithBlock:^{ [self doSomething]; }]; What I'd like to know is the following: if this is true, is there a way that I can avoid the ugliness (aside from using GC)?

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• Python IDLE freezes

  - by ooboo

  This is absolutely frustrating, but I am not sure if the following is an issue only on my machine or with IDLE in general. When attempting to print a long list in the shell, and that could happen by accident while debugging, the program crushes and you have to restart it manually. Even worse, if you have a few editor windows open, it always spawns a few sub-processes, and each of these has to be manually shut down from the task manager. Is there any way to avoid that? I am using Python 3, by the way.

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• Is *not* using the asp.net membership provider a bad idea?

  - by EJB

  Is it generally a really bad idea to not use the built-in asp.net membership provider? I've always rolled my own for my asp.net apps (public facing), and really have not had any problems in doing so. It works, and seems to avoid a layer of complexity. My needs are pretty basic: once setup, the user must use email address and password to login, if they forget it, it will be emailed back to them (a new one). After setup there is little that needs to be done to each user account, but I do need to store several extra fields with each user (full name, telephone and a few other fields etc). The number of users that required login credentials are small (usually just the administrator and a few backups), and everyone else uses the site unauthenticated. What are the big advantages that I might be missing out on by skipping the asp.net membership provider functionality?

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• In Python, how to use a C++ function which returns an allocated array of structs via a ** parameter?

  - by Jon-Eric

  I'd like to use some existing C++ code, NvTriStrip, in a Python tool. SWIG easily handles the functions with simple parameters, but the main function, GenerateStrips, is much more complicated. What do I need to put in the SWIG interface file to indicate that primGroups is really an output parameter and that it must be cleaned up with delete[]? /////////////////////////////////////////////////////////////////////////// // GenerateStrips() // // in_indices: input index list, the indices you would use to render // in_numIndices: number of entries in in_indices // primGroups: array of optimized/stripified PrimitiveGroups // numGroups: number of groups returned // // Be sure to call delete[] on the returned primGroups to avoid leaking mem // bool GenerateStrips( const unsigned short* in_indices, const unsigned int in_numIndices, PrimitiveGroup** primGroups, unsigned short* numGroups, bool validateEnabled = false ); FYI, here is the PrimitiveGroup declaration: enum PrimType { PT_LIST, PT_STRIP, PT_FAN }; struct PrimitiveGroup { PrimType type; unsigned int numIndices; unsigned short* indices; PrimitiveGroup() : type(PT_STRIP), numIndices(0), indices(NULL) {} ~PrimitiveGroup() { if(indices) delete[] indices; indices = NULL; } };

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• Is it possible to dynamically set a static string during *class* Initialisation?

  - by LonnieBest

  I'm trying to dynamically create a connection string during compile time: public static string ConnectionString { get { string connectionString = @"Data Source=" + myLibrary.common.GetExeDir() + @"\Database\db.sdf;"; return connectionString; } } I keep running into type initialisation errors. I was trying to avoid having to set the connection string for all applications that user my code library. The location of the database is different for each project that uses the library. I have code that can determine the correction string, but was wanting run it during compile time. Is this even possible?

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• ASP.NET single quotes are converted to &#39;

  - by Monty

  Note: Most probably this will be a double question, but since I haven't found a clear answer, I'm asking it anyway. In ASP.NET I'd like to add some JavaScript to the onclick event of a CheckBox. I've simplified the case to this: <asp:CheckBox ID="TestCheckBox" runat="server" onclick="alert('test');" Text="Test" /> The resulting HTML is as follows: <input id="MainContainer_TestCheckBox" type="checkbox" name="ctl00$MainContainer$TestCheckBox" onclick="alert(&#39;test&#39;);" /><label for="MainContainer_TestCheckBox">Test</label> What particularly bothers me is that a single quote 'automatically' gets converted into '&#39;'. If I omit the onclick in the markup and assign it in Page_Load, the exact same results show in the HTML. protected void Page_Load(object sender, EventArgs e) { this.TestCheckBox.Attributes["onclick"] = "alert('test');"; } Anyone got a clue about what's happening? Or how to fix/ avoid it?

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• Performance of Managed C++ Vs UnManaged/native C++

  - by bsobaid

  I am writing a very high performance application that handles and processes hundreds of events every millisecond. Is Unmanaged C++ faster than managed c++? and why? Managed C++ deals with CLR instead of OS and CLR takes care of memory management, which simplifies the code and is probably also more efficient than code written by "a programmer" in unmanaged C++? or there is some other reason? When using managed, how can one then avoid dynamic memory allocation, which causes a performance hit, if it is all transparent to the programmer and handled by CLR? So coming back to my question, Is managed C++ more efficient in terms of speed than unmanaged C++ and why?

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• How do I implement .net plugins without using AppDomains?

  - by Abtin Forouzandeh

  Problem statement: Implement a plug-in system that allows the associated assemblies to be overwritten (avoid file locking). In .Net, specific assemblies may not be unloaded, only entire AppDomains may be unloaded. I'm posting this because when I was trying to solve the problem, every solution made reference to using multiple AppDomains. Multiple AppDomains are very hard to implement correctly, even when architected at the start of a project. Also, AppDomains didn't work for me because I needed to transfer Type across domains as a setting for Speech Server worfklow's InvokeWorkflow activity. Unfortunately, sending a type across domains causes the assembly to be injected into the local AppDomain. Also, this is relevant to IIS. IIS has a Shadow Copy setting that allows an executing assembly to be overwritten while its loaded into memory. The problem is that (at least under XP, didnt test on production 2003 servers) when you programmatically load an assembly, the shadow copy doesnt work (because you are loading the DLL, not IIS).

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