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  • how to create local dynamic varables

    - by xielingyun
    this is my code, i want to use eval() to get the rule status and eval() nead local varables, there is many classes inherit class base, so i should to rewrite get_stat() in every class.i just want to avoid this, an idea is to create dynamic varables in get_stat(),eg. in class b it dynamic create var a and b how to create dynamic varables in function? or any other way to avoid this stupid idea i use python 3.2.3, locals() does not work class base(object): def check(self): stat = get_stat() def get_stat(self): pass class b(base): rule = 'a > 5 and b < 3' a = 0 b = 0 def update_data(self, a, b): self.a = a self.b = b def get_stat(self): a = self.a b = self.b return eval(rule) class b(base): rule = 'd > 5 and e < 3' d = 0 e = 0 def update_data(self, d, e): self.d = d self.e = e def get_stat(self): d = self.d e = self.e return eval(rule)

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  • Avoiding Nested Queries

    - by Midhat
    How Important is it to avoid nested queries. I have always learnt to avoid them like a plague. But they are the most natural thing to me. When I am designing a query, the first thing I write is a nested query. Then I convert it to joins, which sometimes takes a lot of time to get right. And rarely gives a big performance improvement (sometimes it does) So are they really so bad. Is there a way to use nested queries without temp tables and filesort

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  • How to better design it ???

    - by Deepak
    public interface IBasePresenter { } public interface IJobViewPresenter : IBasePresenter { } public interface IActivityViewPresenter : IBasePresenter { } public class BaseView { public IBasePresenter Presenter { get; set; } } public class JobView : BaseView { public IJobViewPresenter JobViewPresenter { get { this.Presenter as IJobViewPresenter;} } } public class ActivityView : BaseView { public IActivityViewPresenter ActivityViewPresenter { get { this.Presenter as IActivityViewPresenter;} } } Lets assume that I need a IBasePresenter property on BaseView. Now this property is inherited by JobView and ActivityView but if I need reference to IJobViewPresenter object in these derived classes then I need to type cast IBasePresenter property to IJobViewPresenter or IActivityPresenter (which I want to avoid) or create JobViewPresenter and ActivityViewPresenter on derived classes (as shown above). I want to avoid type casting in derived classes and still have reference to IJobViewPresenter or IActivityViewPresenter and still have IBasePresenter in BaseView. Is there a way I can achieve it ?

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  • Top tips for designing GUIs?

    - by oxbow_lakes
    A while back I read (before I lost it) a great book called GUI Bloopers which was full of examples of bad GUI design but also full of useful tidbits like Don't call something a Dialog one minute and a Popup the next. What top tips would you give for designing/documenting a GUI? It would be particularly useful to hear about widgets you designed to cram readable information into as little screen real-estate as possible. I'm going to roll this off with one of my own: avoid trees (e.g. Swing's JTree) unless you really can't avoid it, or have a unbounded hierarchy of stuff. I have found that users don't find them intuitive and they are hard to navigate and filter. PS. I think this question differs from this one as I'm asking for generalist tips

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  • Why shouldn't I use Flash?

    - by acidzombie24
    I heard many times i should avoid flash for my website. Yet no one has told me a good reason. I searched for reasons and i see many that are not true (such as text in flash are not indexable by search engines) or may not necessarily be true or significant enough (eating more bandwidth. Would a JS equivalent be bigger or smaller?). My site uses flash to playback sound (m4a). I dont have to worry about indexing, the back button not working, etc. But i have feeling there may be other reasons. What are reasons i shouldnt use flash on my website. I'll note one, the fact iphone/itouch and mobile devices does not support it. Not a big deal for most sites and is obvious. What are reason to avoid flash on my site?

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  • Question about best practices and Macros from the book 'C++ Coding Standards'

    - by Victor T.
    From Herb Sutter and Andrei Alexandrescu's 'C++ Coding Standards', Item 16: Avoid Macros under Exceptions for this guideline they wrote: For conditional compilation (e.g., system-dependent parts), avoid littering your code with #ifdefs. Instead, prefer to organize code such that the use of macros drives alternative implementations of one common interface, and then use the interface throughout. I'm having trouble understanding exactly what they mean by this. How can you drive alternate implementations without the use of #ifdef conditional compile macro directives? Can someone provide an example to help illustrate what's being proposed by the above paragraph? Thanks

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  • MVVM - what is the ideal way for usercontrols to talk to each other

    - by Sandbox
    I have a a user control which contains sevral other user controls. I am using MVVM. Each user control has a corresponding VM. How do these user controls send information to each other. I want to avoid writing any code in the xaml code behind. Particularly I am interested in how the controls (inside the main user control) will talk to each other and how will they talk to the container user control. EDIT: I know that using events-delegates will help me solve this issue. But, I want to avoid writing any code in xaml code-behind.

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  • just-in-time list

    - by intuited
    I'd like to know if there is a class available, either in the standard library or in pypi, that fits this description. The constructor would take an iterator. It would implement the container protocol (ie _getitem_, _len_, etc), so that slices, length, etc., would work. In doing so, it would iterate and retain just enough values from its constructor argument to provide whatever information was requested. So if jitlist[6] was requested, it would call self.source.next() 7 times, save those elements in its list, and return the last one. This would allow downstream code to use it as a list, but avoid unnecessarily instantiating a list for cases where list functionality was not needed, and avoid allocating memory for the entire list if only a few members ended up being requested. It seems like a pretty easy one to write, but it also seems useful enough that it's likely that someone would have already made it available in a module.

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  • Including the functionality of a tool within another program?

    - by darren
    Hi there I would like to write an application, for my own interest, that graphically visualizes some network concepts. Basically I would like to show the output from tools like ping, traceroute and nmap. The most obvious approach seems to be to use pipes to call out to these tools from my C program, and process the information they return. However, I would like to avoid this heavy-handed approach if possible. My question is, is it possible to somehow link against these tools, or are there APIs that can be used to gain programatic access instead? If so, is this behavior available on a tool-by-tool basis only? One reason for wanting to do this is to keep everything in a single process / address space and to avoid dependance on these external tools. For example, if I wrote an iphone application, I would not be able to spawn processes to call out to the external tools themselves. Thanks for any advice or suggestions.

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  • Save in Sessions to reduce database load

    - by Kovu
    at the moment I try to reduce the load on my database extremly, so I had a look in my website and think about - what database calls can I try to avoid. So is there a rule for that? Sould I save every information in a Session that is nearly never changed? e.g.: The User-Table is a 35-coloumn-table which I need so often in so different ways, that in the moment I got this user-object at nearly every PageLoad AND in the master-site-page-load (Settings, display the username for a welcome message, colors etc etc.). So is that good to avoid the database query here, save the User-Object in a Session and call it from the session - and of course destroy the session whereever the User-Object get changed (e.g. User change his settings)?

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  • Python grab class in class definition.

    - by epochwolf
    I don't even know how to explain this, so here is the code I'm trying. class Test: type = self.__name__ #self doesn't work, how do I get a reference to Test? class Test2(Test): pass #Test2.type should return "Test2" The reason I'm even trying this is I'm working on creating a base class for an orm I'm using. I want to avoid defining the table name for every model I have. Also knowing what the limits of python is will help me avoid wasting time trying impossible things.

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  • Implementing Tagging using Core Data on the iPhone

    - by Jonathan Penn
    I have an application that uses CoreData and I'm trying to figure out the best way to implement tagging and filtering by tag. For my purposes, if I was doing this in raw SQLite I would only need three tables, tags, item_tags and of course my items table. Then filtering would be as simple as joining between the three tables where only items are related to the given tags. Quite straightforward. But, is there a way to do this in CoreData and utilizing NSFetchedResultsController? It doesn't seem that NSPredicate give you the ability to filter through joins. NSPredicate's aren't full SQL anyway so I'm probably barking up the wrong tree there. I'm trying to avoid reimplementing my app using SQLite without CoreData since I'm enjoying the performance CoreData gives me in other areas. Yes, I did consider (and built a test implementation) diving into the raw SQLite that CoreData generates, but that's not future proof and I want to avoid that, too. Has anyone else tried to tackle tagging/filtering with CoreData in a UITableView with NSFetchedResultsController

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  • How do you enter something at a DOS prompt Programmatically?

    - by LonnieBest
    I have program, that must interact with at DOS program before my program can continue what it is doing. I'm trying to avoid my user from having to interact with this dos program. So, I created a .bat file that does everything I need to do except for the last step which still requires user interaction that I'm trying to avoid. Specifically, the command I type ends up at a dos prompt where I need to automatically enter y and then enter (to say yes to the prompt) and then I want to exit out. Is there any way that I can make this happen automatically without my user having to enter y and enter? Ideally, I'd like to have the console-window even pop up while this is going on.

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  • iPhone app launch times and Core Data migration

    - by sehugg
    I have a Core Data application which I plan to update with a new schema. The lightweight migration seems to work, but it takes time proportional to the amount of data in the database. This occurs in the didFinishLaunchingWithOptions phase of the app. I want to avoid <app> failed to launch in time problems, so I assume I cannot keep the migration in the didFinishLaunchingWithOptions method. I assume the best method would involve performing the migration in a background thread. I assume also that I'd need to defer loading of the main ViewController until the loading completes to avoid using the managedObjectContext until initialization completes. Does this make sense, and is there example code (maybe in Apple sample projects) of this sort of initialization?

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  • new image makes http request even though cached?

    - by joshs
    I have a javascript slide show that creates the next slide dynamically and then moves it into view. Since the images are actually sprites, the src is transparent.png and the actual image is mapped via background:url(.. in css. Everytime (well, most of the time) the script creates a new Element, Firefox makes an http request for transparent.png. I have a far-future expires header, and Firefox is respecting all other files' expiries. Is there a way to avoid these unnecessary requests. Even though the server is returning 304 unmodified responses, it would be nice if Firefox would respect the expiries on dynamically created images. I suspect that if I injected a simple string instead of using new Element, this might solve the problem, but I use some methods on Prototypes extended Element object, so I would like to avoid a bunch of html strings in my js file. This is a nit-picky question, but I'm working on front-end optimization now, so I thought I would address it. Thanks.

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  • ASP.NET request extension type

    - by Krishna
    Hello, I am working on a large web application which I have recently shelved tons of .aspx pages from the project. To avoid page not found error, I added these entities in the xml which came around 300+ in count. I wrote a http module that checks the request url in the xml entities and if they are found, my module is going to redirect the request to respective new pages. Everything works great, but my collection is getting iterated for all the requests, I mean for each and every .jpg, .css, .js, .ico, .pdf etc. Is there any object or property in .net that can tell the type of request that user requested for like HttpContext.request.type. So that I can avoid checking the request for all unwanted file types.

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  • Read the "Human friendly" text of a WebPage

    - by oidfrosty
    I need to read the final user page text, for example : "&#x73;&#x74;&#x61;&#x63;&#x6B;&#x6F;&#x76;&#x65;&#x72;&#x66;&#x6C;&#x6F;&#x77;&#x2E;&#x63;&#x6F;&#x6D;" is displayed as "stackoverflow.com". the aim is to avoid the use of script/encoding to avoid my filters it will be done with a content filtering proxy. i was thinking about injecting a script in the page

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  • IOS SDK : first advices for beginners

    - by VdesmedT
    I too often answer the same kind of questions regarding basic topics like memory management, UITableView, Interface Orientation, MVC, etc... I understand very well that everyone starting with that SDK is too exited about getting its hand on it but a few reading would save them hours of debugging and the frustration that come along with the feeling that "We miss something here". I'd like experience users to share the few small articles, white papers, docs, book chapters that helps other save their time and avoid frustration. My first vote would be for : IOS Memory Management Guide View Controller Programming Guide Table View Guide And as a General recommendation, read the Overview section that come along with every class documention in the reference library, they contains most of what you need to know to avoid big traps !

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  • How do you make your Java application memory efficient?

    - by Boune
    How do you optimize the heap size usage of an application that has a lot (millions) of long-lived objects? (big cache, loading lots of records from a db) Use the right data type Avoid java.lang.String to represent other data types Avoid duplicated objects Use enums if the values are known in advance Use object pools String.intern() (good idea?) Load/keep only the objects you need I am looking for general programming or Java specific answers. No funky compiler switch. Edit: Optimize the memory representation of a POJO that can appear millions of times in the heap. Use cases Load a huge csv file in memory (converted into POJOs) Use hibernate to retrieve million of records from a database Resume of answers: Use flyweight pattern Copy on write Instead of loading 10M objects with 3 properties, is it more efficient to have 3 arrays (or other data structure) of size 10M? (Could be a pain to manipulate data but if you are really short on memory...)

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  • How to read the whole istream correctly?

    - by L.Lawliet
    Here is a simple code to print all characters of a txt file on screen: #include <iostream> #include <fstream> #include <string> using namespace std; int main() { int **i; int j,k; char a; ifstream test("test.txt", ios::binary); while((a=test.get())!=-1)//if I use "while(!test.eof())" here, how to avoid the output of the last character(-1) to std::cout, or any ostream objects? { putchar(a);//also change this to putchar(test.get()); } getchar(); } As I noted in the code, if I use "test.eof()" to judge the end of test.txt, I'll always get an extra blank at the end of the output. How to avoid it?

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  • Why this button doesn't cause triple postback?

    - by focus
    We have developed a page with a asp.net and debugging it accidentally we have discovered on our page button with the next code on onclik attribute onclick="__doPostBack('ctl00$FormPlace$m_userTaskMarkAsUnreadButton',''); __doPostBack('ctl00$FormPlace$m_userTaskMarkAsUnreadButton','');WebForm_DoPostBackWithOptions(new WebForm_PostBackOptions("ctl00$FormPlace$m_userTaskMarkAsUnreadButton", "", true, "", "", false, false))" It seems that the button do three postbacks but when we click it only cause on postback. With this code seems that de button will cause three postbacks!! We have try it with Internet Explorer and Firefox and the button only cause on postback always. Are browsers who avoid that the button do three postback ? Or Is Asp.net server who avoid the three postback? We don't understand why the button behaves correctly if onclick attribute has three call to do Postbacks. Thanks

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  • Django: How/Where to store a value for a session without unnecessary DB hits

    - by GerardJP
    Hi all, I have an extended userprofile with AUTH_PROFILE_MODULE (ref: http://tinyurl.com/yhracqq) I would like to set a user.is_guru() method similar to user.is_active(). This would results for al views (or rather templates) to e.g. disable/enable certain user messages, displaying of widgets, etc. The boolean is stored in the extended user profile model, but I want to avoid hitting the DB for every view. So the questions is .. Do I use a context_processor, a template tag, session_dict or what have you to, possible cached, store this info for the duration of the users visit. Note: I dont have performance issues, so it's definitely filed under premature optimization. I just want to avoid generating extra work in the future :). Any pointers are very welcome. Thanx and greetz! Gerard.

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