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  • How should I declare default values for instance variables in Python?

    - by int3
    Should I give my class members default values like this: class Foo: num = 1 or like this? class Foo: def __init__(self): self.num = 1 In this question I discovered that in both cases, bar = Foo() bar.num += 1 is a well-defined operation. I understand that the first method will give me a class variable while the second one will not. However, if I do not require a class variable, but only need to set a default value for my instance variables, are both methods equally good? Or one of them more 'pythonic' than the other? One thing I've noticed is that in the Django tutorial, they use the second method to declare Models. Personally I think the second method is more elegant, but I'd like to know what the 'standard' way is.

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  • Bookmarkabale ajax calls with MVC routing

    - by devzero
    I have a page with a menu that uses JQuery AJAX calls to populate the page with. To reflect any changes I update the URL with a #... instead of ?... or /... So an URL that originally reads : htpp://localhost/pages/index/id=1 would look like : http://localhost/#pages/index/id=1. If a user bookmarks this, and later comes back to the page, I wonder if it's possible to use the second URL in my route decoding, or if I have to load it blank, then use the same JS/Ajax to populate the page? In my mind it is problematic to use Ajax in these cases if a user copies the link and mails it to a friend with JavaScript disabled. edit#1: Fixed some spelling.

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  • When does it make sense to use a map?

    - by kiwicptn
    I am trying to round up cases when it makes sense to use a map (set of key-value entries). So far I have two categories (see below). Assuming more exist, what are they? Please limit each answer to one unique category and put up an example. Property values (like a bean) age -> 30 sex -> male loc -> calgary Presence, with O(1) performance peter -> 1 john -> 1 paul -> 1

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  • Why are difference lists more efficient than regular concatenation?

    - by Craig Innes
    I am currently working my way through the Learn you a haskell book online, and have come to a chapter where the author is explaining that some list concatenations can be ineffiecient: For example ((((a ++ b) ++ c) ++ d) ++ e) ++ f Is supposedly inefficient. The solution the author comes up with is to use 'difference lists' defined as newtype DiffList a = DiffList {getDiffList :: [a] -> [a] } instance Monoid (DiffList a) where mempty = DiffList (\xs -> [] ++ xs) (DiffList f) `mappend` (DiffList g) = DiffList (\xs -> f (g xs)) I am struggling to understand why DiffList is more computationally efficient than a simple concatenation in some cases. Could someone explain to me in simple terms why the above example is so inefficient, and in what way the DiffList solves this problem?

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  • GCC: visibility of symbols in standalone C++ applications

    - by Albert
    Hi, Because of a strange C++ warning about the visibility of some symbols and an interesting answer, linking to a paper which describes the different visibility types and cases (section 2.2.4 is about C++ classes), I started to wonder if it is needed for a standalone application to export symbols at all (except main - or is that needed?). Why exactly are they needed to be exported in standalone applications? Is "an exported symbol" an synomym for "visible symbol"? I.e. a hidden symbol is a symbol which is not exported? Do the object files already differ between visible symbols and hidden symbols? Or is this made at the linking step, so that only the visible symbols are exported? Does the visibility of symbols matter in case for debug information? Or is that completely independent, i.e. I would also get a nice backtrace if I have all symbols hidden? How is STABS/DWARF related to the visibility of symbols?

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  • Need some testcases on solving this problem

    - by user285825
    I am trying to solve the minesweeper problem of acm problemset archive, http://uva,onlinejudge,org/index,php?option=com_onlinejudge&Itemid=8&category=13&page=show_problem&problem=1130 I tested with all the possible cases that I can imagine of: 1, minimum 1 1 , 1 1 # 2, maximum upto 100 upto 100 repeat until 100 3, for each position I test for mine 4 4 ,,, ,,,, ,,,, 4 4 ,#,, ,,,, ,,,, ,,,, lastly 4 4 ,,,, ,,,, ,,,, ,,,# 4, for each postion I put a ',' and surround it with mines 4 4 ,### # # # 4 4 , # # # lastly 4 4 # # # , I thought that these are reasonable and representative sets of testcases, But still Wrong answer, I am not sure what else could I test for, I would be glad if someone throw some light on further strategy to test this thing,

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  • PHP registration script: verifying and telling the user what went wrong

    - by Maxime
    Hi, I'm building a registration script and I want to insert the user's input (username, mail) ONLY if it's not already in the database. What I usually do in such cases is a request to see if something's already there, something like: "SELECT * FROM things WHERE thing_name = '$treated_user_input'". I have two fields that need to be unique this time though. Is there a way to do only one SELECT request and still be able to tell the user exactly what field went wrong? Or do I have to do one request per unique field? Thanks for your answers.

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  • ActiveRecord Create (not !) Throwing Exception on Validation

    - by myferalprofessor
    So I'm using ActiveRecord model validations to validate a form in a RESTful application. I have a create action that does: @association = Association.new and the receiving end of the form creates a data hash of attributes from the form parameters to save to the database using: @association = user.associations.create(data) I want to simply render the create action if validation fails. The problem is that the .create (not !) method is throwing an exception in cases where the model validation fails. Example: validates_format_of :url, :with => /(^$)|(^(http|https):\/\/[a-z0-9]+([\-\.]{1}[a-z0-9]+)*\.[a-z]{2,5}(([0-9]{1,5})?\/.*)?$)/ix, :message => "Your url doesn't seem valid." in the model produces: ActiveRecord::RecordInvalid Exception: Validation failed: Url Your url doesn't seem valid. I thought .create! is supposed throw an exception whereas .create is not. Am I missing something here? Ruby 1.8.7 patchlevel 173 & rails 2.3.3

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  • Is it possible to raise an error if a variable assignment in a select returns multiple values?

    - by Brann
    I just found a bug on one of my softwares where I had forgotten a where clause. The code was something like that : declare @foo bigint declare @bar bigint select @foo = foo, @bar=bar from tbFooBar where (....a long list of condition goes there) (... and an extra condition should have went there but I forgot it) Unfortunately, the where clause I forgot was useful in very specific corner cases and the code went through testing successfully. Eventually, the query returned two values instead of one, and the resulting bug was a nightmare to track down (as it was very difficult to reproduce, and it wasn't obvious at all that this specific stored procedure was causing the issue we spotted) Debugging would have been a lot easier if the @foo=foo had raised an exception instead of silently assigning the first value out of multiple rows. Why is that this way? I can't think of a situation where one would actually want to do that without raising an error (bearing in mind the clauses 'distinct' and 'top' are there for a reason) And is there a way to make sql server 2008 raise an error if this situation occurs ?

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  • Preventing Race Conditions

    - by Qua
    I'm using the built-in ajax functionality of MVC2. Basically the user types a search query, and on every key press a set of results for the query is shown. This works fine in almost all cases, but sometimes the server is a bit slow with a single response, and thus the result for the next key stroke is returned before the previous. When the previous key stroke result set is finally returned to the client it will overwrite the results for the newer search query that should actually have been shown. My code follows more or less along these lines: <% using (Ajax.BeginForm("SearchUser", null, new AjaxOptions() { UpdateTargetId = "findUserResults" }, new { id = "findUserAjaxForm" })) {%> Every keystroke submits this form and thus outputs the results in the 'findUserResults' element. How can I prevent older results from being displayed while still making use of the built-in functions provided in MVC2?

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  • Making a relevant search of text in database using regex

    - by madphp
    Can anyone tell me how I could count the possible instances of a keyword in a block of text? I've split a search term up into separate tokens, so just need to run through and do a count for every instance and removing punctuation or other special characters when making the count. Secondly, if someone has inserted search terms surrounded by double quotes, i want to be able to skip explode, but just count instances of that exact phrase. It doesn't have to be case sensitive and I would like to remove punctuation from the phrase when doing the count. Thirdly, in both cases i want to be able to ignore wordpress and html tags. Lastly, if anyone know any good tutorials for relevant searches that answer the questions above, that would cool too. I've got this far. $results = $wpdb->get_results($sql); $tokens = explode('search_terms'); // Re-arrange Relevant Results foreach ($results As $forum_topic){ foreach($tokens As $token){ // count tokens in topic_title if ($token ){ } } }

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  • PHP eval() code in between <?php ?> from database

    - by kr1zmo
    Some of you may be annoyed with this question, and claim it's unsafe blah blah. I want to be able to put php into the database and run it. I have to do this because I store page layouts in the database and each our different for each other, however in some cases I want to use dynamic content for some of the pages. assume $query_from_db is the string returned from the database. php should only eval() the code in between <?php and ?> $query_from_db = '<div> <?php //php to run function dosomething() { //bleh } ?> </div> '; php echo eval($query_from_db);

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  • XML Schema Header & Namespace Config

    - by zharvey
    Migrating from DTD to XSD and for some reason the transition is a bumpy one. I understand how to define the schema once I'm inside the <xs:schema> root tag, but getting past the header & namespace declaration stuff is proving to be especially confusing for me. I have been trying to follow the well-laid out tutorial on W3S but even that tutorial seems to assume a lot of knowledge up front. I guess what I'm looking for is a King's English explanation of which attributes do what, where they go, and why: xmlns xmlns:xs xmlns:xsi targetNamespace xsi:schemaLocation And in some cases I see different variations of these elements/attributes, such as xsi which seems to have two different notations like xsi:schemaLocation="..." and xs:import schemaLocation="...". I guess between all these slight variations I can't seem to make heads or tails of what each of these does. Thanks in advance for bringing any clarity to this confusion!

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  • Is there a browser-agnostic way to detect client-side script errors with Watin?

    - by Michael
    We're using WatiN to test our web portals. During the course of an E2E test, we'll occasionally see client-side script errors on the IE status bar. I'd like to chain a handler onto the script error event and record the error for later analysis and bug filing. Problem is, I don't know that there's a global script error event or how to chain into it. And if there's not a browser-agnostic way to accomplish this, I can create MyIE and MyFF subclasses but then this becomes two browser-specific questions. In essence, I'm thinking of something like this entirely made-up call: browser.ScriptEngine.SetCustomErrorHandler(LogScriptingError); ... where LogScriptErrors is my code that does the obvious. Many of our client-side scripting errors don't necessarily prevent the test from continuing (a pretty UI element didn't animate, for example, but the underlying form is still submittable), so I'd like to log the error and forge ahead in most cases.

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  • Python - react to custom keyboard interrupt

    - by flixic
    Hello. I am writing python chatbot that displays output through console. Every half second it asks server for updates, and responds to message. In the console I can see chat log. This is sufficient in most cases, however, sometimes I want to interrupt normal workflow and write custom chat answer myself. I would love to be able to press a button (or combination) that would switch to "custom reply mode". What is the best way to do that, or achieve similar result? Thanks a lot!

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  • When to use memberEnd and when navigableOwnedEnd (in Altova notation) in an UML class diagram?

    - by Ivan
    I've download a trial of Altova UModel and am starting using UML. As a practical beginning I am modelling a personal information manager application, which includes a web bookmark managing. A Bookmark can belong to many (or no) Tags at once and a Tag can contain many (or no if all the bookmarks it contained were deleted) bookmarks. The relation has to be both-way navigable - a user has to be able to see all Bookmarks with a particular Tags ans all Tags of a Bookmark. What is the correct UML relation between Bookmark and Tag classes? As far as I understand UML now, it is an Association (not an Aggregation). But for a 2-way navigable many-to-many relation I can specify ends roles as "memberEnd" or "when navigableOwnedEnd", graphically the connection looks the same in both cases (an arrow) (which as I understand means navigability) but a property appears in the class box in case only when "memberEnd" is used. How should I specif it in the model If I mean both-way navigable many-to-many relation there?

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  • What algorithms compute directions from point A to point B on a map?

    - by A. Rex
    How do map providers (such as Google or Yahoo! Maps) suggest directions? I mean, they probably have real-world data in some form, certainly including distances but also perhaps things like driving speeds, presence of sidewalks, train schedules, etc. But suppose the data were in a simpler format, say a very large directed graph with edge weights reflecting distances. I want to be able to quickly compute directions from one arbitrary point to another. Sometimes these points will be close together (within one city) while sometimes they will be far apart (cross-country). Graph algorithms like Dijkstra's algorithm will not work because the graph is enormous. Luckily, heuristic algorithms like A* will probably work. However, our data is very structured, and perhaps some kind of tiered approach might work? (For example, store precomputed directions between certain "key" points far apart, as well as some local directions. Then directions for two far-away points will involve local directions to a key points, global directions to another key point, and then local directions again.) What algorithms are actually used in practice? PS. This question was motivated by finding quirks in online mapping directions. Contrary to the triangle inequality, sometimes Google Maps thinks that X-Z takes longer and is farther than using an intermediate point as in X-Y-Z. But maybe their walking directions optimize for another parameter, too? PPS. Here's another violation of the triangle inequality that suggests (to me) that they use some kind of tiered approach: X-Z versus X-Y-Z. The former seems to use prominent Boulevard de Sebastopol even though it's slightly out of the way. (Edit: this example doesn't work anymore, but did at the time of the original post. The one above still works as of early November 2009.)

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  • Efficient multiple services exposed over c# .NET remoting using more channels or end points?

    - by wb
    I am using remoting over TCP for a prototype distributed server application where I want to have varying multiple services exposed from each remoting server process. In some cases I want the services running from the same process but I don't want whatever is using the service to care about that. I am wondering is it more efficient to have multiple services in the same process going over the same remoting channel distinguished by endpoint URI/URL or should I be creating new channels on different ports for each service in the same process? Using up ports isn't so much of a problem as the number of services will be low and the network and machine configuration is completely controlled. Also its not clear to me if remoting sends the URI string for every single message or just at connection time, and whether if the remoting framework is intelligent enough to reduce work if calls are made on the same machine and even the same process? Thanks in advance.

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  • Prototype and jQuery concatenation failure

    - by Corey Hart
    I found something strange when trying to concatenate prototype and jQuery. It seems as though when concatenated, the $ jquery reference doesn't get overwritten by prototype. I've built two test cases to single this out, and it's failing in Chrome8 and FF 3.6. Test Case 1 - Without Concatenation jQuery and Prototype are loaded separately with different script tags. jQuery is loaded first, Prototype second. Test Case 2 - With Concatenation jQuery and Prototype are concatenated into a single file, and loaded with a single script tag. jQuery is first in the script, and prototype is added second. These should act identically, but the second test is throwing errors because the $ function in prototype doesn't overwrite the $ jquery reference. Did I set these up wrong, or are browsers rendering javascript differently when it's all in the same file?

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  • ASP.NET MVC: What is the correct way to redirect to pages/actions in MVC?

    - by Mark Redman
    I am fairly new to MVC but not sure exactly which Redirect... replaces the standard redirect used in WebForms ie the standard Response.Redirect() For instance, I need to redirect to other pages in a couple of scenarios: 1) WHen the user logs out (Forms signout in Action) I want to redirect to a login page 2) In a Controller or base Controller event eg Initialze, I want to redirect to another page (AbsoluteRootUrl + Controller + Action) It seems that multiple redirects get called in some cases which causes errors, something to do with the fact a page is already being redirected? How can cancel the current request and just redirect?

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  • Duplicate ID/indexes and looping

    - by Justin Alexander
    I realize having two elements in the same html doc with the same ID is wrong, bad, immoral, and will lead to global warming. But... I'm trying to write an XSS widgit, so I really have no control over the quality of the parent web page. I loop through document.images to retrieve a list of images on the page. I perform an action on each one. for(img in document.images){ ... } i've also tried for(var i=0;i<document.images.length;i++){ ... } in both cases it allows me to loop through all of the elements, BUT when trying trying to reference an object with a duplicate ID, I always get the first (in order of the html). When using debugger in IE8 i'm able to see that both elements ARE listed, but that they both have the same index (in IE the index of the document.images is either sequential or matches the image ID) Does anyone have a better solution?

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  • flash.media.Sound.play takes long time to return

    - by Fire Lancer
    I'm trying to play some sounds in my flash project through action script. However for some reason in my code the call to Sound.play takes from 40ms to over 100ms in extreme cases, which is obviously more than enough to be very noticeable whenever a sound is played. This happens every time a sound is played, not just when that sound is first played, so I dont think its because the Sound object is still loading data or anything like that... At the start I have this to load the sound: class MyClass { [Embed(source='data/test_snd.mp3')] private var TestSound:Class; private var testSound:Sound;//flash.media.Sound public function MyClass() { testSound = new TestSound(); } Then im just using the play method of the sound object to play it later on. testSound.play();//seems to take a long time to return This as far as I can tell is following the same process as other Flash programs I found, however none of them seem to have this problem. Is there something that I've missed that would cause the play() method to be so slow?

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  • How do I get the path of the current executed file in python?

    - by Sorin Sbarnea
    This may seam a newbie question but it is not. It looks that common approaches are not always working: Currently I know only two options but none of them looks to work an all cases. sys.argv[0] This means using path = os.path.abspath(os.path.dirname(sys.argv[0])) but this does not work if you are running from another python script from another directory, and this can really happen in real life. __file__ this means that path = os.path.abspath(os.path.dirname(__file__)) but I found that this doesn't work: py2exe that doesn't have a __file__ attribute but there is an workaround. when you run from IDLE with execute() there is no __file__ attribute OS X 10.6 where I get NameError: global name '__file__' is not defined Related questions with incomplete answers: http://stackoverflow.com/questions/1296501/python-find-path-to-file-being-run http://stackoverflow.com/questions/1483827/python-path-to-current-file-depends-on-how-i-execute-the-program http://stackoverflow.com/questions/2259503/how-to-know-the-path-of-the-running-script-in-python http://stackoverflow.com/questions/509742/python-chdir-to-dir-the-py-script-is-in

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  • SQL select all items of an owner from an item-to-owner table

    - by kdobrev
    I have a table bike_to_owner. I would like to select current items owned by a specific user. Table structure is CREATE TABLE IF NOT EXISTS `bike_to_owner` ( `bike_id` int(10) unsigned NOT NULL, `user_id` int(10) unsigned NOT NULL, `last_change_date` date NOT NULL, PRIMARY KEY (`bike_id`,`user_id`,`last_change_date`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci; In the profile page of the user I would like to display all his/her current possessions. I wrote this statement: SELECT `bike_id`,`user_id`,max(last_change_date) FROM `bike_to_owner` WHERE `user_id` = 3 group by `last_change_date` but i'm not quite sure it works correctly in all cases. Can you please verify this is correct and if not suggest me something better. Using php/mysql. Thanks in advance!

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  • Problem with literal arguments in the PATTERN string for a python 2to3 fixer

    - by Zxaos
    Hi folks. I'm writing a fixer for the 2to3 tool in python. In my pattern string, I have a section where I'd like to match an empty string as an argument, or an empty unicode string. The relevant chunk of my pattern looks like: (args='""' | args='u""') My issue is the second option never matches. Even if it's alone, it won't match. However, if I simply say args=any and then output args, I can catch cases where args is exactly equal to the second option. Is there some weird unicode handling thing going on? Why won't the second literal option ever match?

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