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  • Concatenation of many lists in Python

    - by Space_C0wb0y
    Suppose i have a function like this: def getNeighbors(vertex) which returns a list of vertices that are neighbors of the given vertex. Now i want to create a list with all the neighbors of the neighbors. I do that like this: listOfNeighborsNeighbors = [] for neighborVertex in getNeighbors(vertex): listOfNeighborsNeighbors.append(getNeighbors(neighborsVertex)) Is there a more pythonic way to do that?

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  • How to set a predefined value in a form in Rails

    - by marco
    So I just got started in Rails, and I'm trying to create an Object (a book_loan in my case) with a Form. The thing is that I get to this form by clicking on a book, so I pass the book_id as a parameter, like localhost:3000/loans/new?id=1. Now I don't want the user to be able to set the book id field in the form, since I already know the id. So my question is how to set the value in the form. I have been trying things like: <% form_for(@loan) do |f| %> <%= f.error_messages %> ... <%= @loan.book_id = params[:id] %> <%= f.submit 'Create' %> <% end %> without any success. Does anybody have a hint for me?

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  • Understanding Scope on Scala's For Loops (For Comprehension)

    - by T. Stone
    In Chapter 3 of Programming Scala, the author gives two examples of for loops / for comprehensions, but switches between using ()'s and {}'s. Why is this the case, as these inherently look like they're doing the same thing? Is there a reason breed <- dogBreeds is on the 2nd line in example #2? // #1 ()'s for (breed <- dogBreeds if breed.contains("Terrier"); if !breed.startsWith("Yorkshire") ) println(breed) // #2 {}'s for { breed <- dogBreeds upcasedBreed = breed.toUpperCase() } println(upcasedBreed)

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  • Should we or should we not check in the classes folder in WEB-INF directory into SVN?

    - by Vatsala
    I use SVN, and am learning how to use it along with eclipse IDE. The first time I add classes to my package, there is no problem, the generated class files get into SVN smoothly. The moment I edit them, I get this message - "WEB-INF/classes" is obstructed. I try the "clean-up" command and the clean up command says "WEB-INF/classes" folder is locked. I use TortoiseSVN as my SVN client. I know why this is happening. It probably because the Eclipse overwrites all the files while generating classes and then causes this - Is it inappropriate to commit the class files into SVN? If not, what should I do to commit these class files smoothly?

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  • Python - a clean approach to this problem?

    - by Seafoid
    Hi, I am having trouble picking the best data structure for solving a problem. The problem is as below: I have a nested list of identity codes where the sublists are of varying length. li = [['abc', 'ghi', 'lmn'], ['kop'], ['hgi', 'ghy']] I have a file with two entries on each line; an identity code and a number. abc 2.93 ghi 3.87 lmn 5.96 Each sublist represents a cluster. I wish to select the i.d. from each sublist with the highest number associated with it, append that i.d. to a new list and ultimately write it to a new file. What data structure should the file with numbers be read in as? Also, how would you iterate over said data structure to return the i.d. with the highest number that matches the i.d. within a sublist? Thanks, S :-)

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  • How to improve the speed of a loop containing a sqlalchemy query statement as conditional

    - by LtPinback
    This loop checks if a record is in the sqlite database and builds a list of dictionaries for those records that are missing and then executes a multiple insert statement with the list. This works but it is very slow (at least i think it is slow) as it takes 5 minutes to loop over 3500 queries. I am a complete newbie in python, sqlite and sqlalchemy so I wonder if there is a faster way of doing this. list_dict = [] session = Session() for data in data_list: if session.query(Class_object).filter(Class_object.column_name_01 == data[2]).filter(Class_object.column_name_00 == an_id).count() == 0: list_dict.append({'column_name_00':a_id, 'column_name_01':data[2]}) conn = engine.connect() conn.execute(prices.insert(),list_dict) conn.close() session.close() edit: I moved session = Session() outside the loop. Did not make a difference.

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  • What is/are the Scala way(s) to implement this Java "byte[] to Hex" class

    - by nicerobot
    I'm specifically interested in Scala (2.8) techniques for building strings with formats as well as interesting ways to make such a capability easily accessible where it's useful (lists of bytes, String, ...?).. public class Hex { public static String valueOf (final byte buf[]) { if (null == buf) { return null; } final StringBuilder sb = new StringBuilder(buf.length * 2); for (final byte b : buf) { sb.append(String.format("%02X", b & 0xff)); } return sb.toString(); } public static String valueOf (final Byteable o) { return valueOf(o.toByteArray()); } } This is only a learning exercise (so the utility and implementation of the Java isn't a concern.) Thanks

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  • creating a vector with references to some of the elements of another vector

    - by memC
    hi, I have stored instances of class A in a std:vector, vec_A as vec_A.push_back(A(i)). The code is shown below. Now, I want to store references some of the instances of class A (in vec_A) in another vector or another array. For example, if the A.getNumber() returns 4, 7, 2 , I want to put a reference to that instance of A in another vector, say std:vector<A*> filtered_A or an array. Can someone sow me how to do this?? Thanks! class A { public: int getNumber(); A(int val); ~A(){}; private: int num; }; A::A(int val){ num = val; }; int A::getNumber(){ return num; }; int main(){ int i =0; int num; std::vector<A> vec_A; for ( i = 0; i < 10; i++){ vec_A.push_back(A(i)); } std::cout << "\nPress RETURN to continue..."; std::cin.get(); return 0; }

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  • Java: how to initialize String[]?

    - by Heoa
    Error % javac StringTest.java StringTest.java:4: variable errorSoon might not have been initialized errorSoon[0] = "Error, why?"; Code public class StringTest { public static void main(String[] args) { String[] errorSoon; errorSoon[0] = "Error, why?"; } }

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  • Applying a function that may fail to all values in a list

    - by Egwor
    I want to apply a function f to a list of values, however function f might randomly fail (it is in effect making a call out to a service in the cloud). I thought I'd want to use something like map, but I want to apply the function to all elements in the list and afterwards, I want to know which ones failed and which were successful. Currently I am wrapping the response objects of the function f with an error pair which I could then effectively unzip afterwards i.e. something like g : (a->b) -> a -> [ b, errorBoolean] f : a-> b and then to run the code ... map g (xs) Is there a better way to do this? The other alternative approach was to iterate over the values in the array and then return a pair of arrays, one which listed the successful values and one which listed the failures. To me, this seems to be something that ought to be fairly common. Alternatively I could return some special value. What's the best practice in dealing with this??

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  • jQuery: Freezing/Disabling all events temporarily?

    - by Legend
    I have the following usecase: A div with some buttons When the user clicks on a button, a popup is shown and the background div is faded out to 0.5 opacity The problem is that when the popup comes in, the user is still able to click on the background buttons. At this point, I can remove the entire DIV temporarily but I don't want to do that. Is there anyway I can disable all the previously attached events and then add event handlers ONLY to the current popup? (I mean something like a close button should still work on a popup) Any suggestions?

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  • Java queue and multi-dimension array

    - by javaLearner.java
    First of all, this is my code (just started learning java): Queue<String> qe = new LinkedList<String>(); qe.add("b"); qe.add("a"); qe.add("c"); qe.add("d"); qe.add("e"); My question: Is it possible to add element to the queue with two values, like: qe.add("a","1"); // where 1 is integer So, that I know element "a" have value 1. If I want to add a number let say "2" to element a, I will have like a = 3. If this cant be done, what else in java classes that can handle this? I tried to use multi-dimention array, but its kinda hard to do the queue, like pop, push etc. (Maybe I am wrong) How to call specific element in the queue? Like, call element a, to check its value. [Note] Please don't give me links that ask me to read java docs. I was reading, and I still dont get it. The reason why I ask here is because, I know I can find the answer faster and easier.

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  • C#:Saving image to folder

    - by Meko
    HI. I know this is simple question but when I use FirstPersonTestImage.Save(IIdComboBox.Text + "-" + i + ".jpg"); it works and saves file to folder where is the .exe file . But I want to save it to specific folder like /photo/IO-66/ and tryed to use String StudentPath = PhotoPath + IGroupNoComboBox.Text + "/" + IIdComboBox.Text + "/" + IIdComboBox.Text + "-" + i + ".jpg"; FirstPersonTestImage.Save(StudentPath); BUt it gives An unhandled exception of type 'System.Runtime.InteropServices.ExternalException' occurred in System.Drawing.dll How can I solve this problem? Is is about folder path ? or using "/" ? EDIT Here My code for creating and checking existing or not folder if (!System.IO.Directory.Exists(PhotoPath + "/" + IGroupNoComboBox.Text.ToString().Trim())) { Directory.CreateDirectory(PhotoPath + "/" + IGroupNoComboBox.Text.ToString().Trim()); } if (!System.IO.Directory.Exists(PhotoPath + "/" + IGroupNoComboBox.Text.ToString().Trim()+ "/" + IIdComboBox.Text.ToString().Trim() + "/")) { Directory.CreateDirectory(PhotoPath + "/" + IGroupNoComboBox.Text.ToString().Trim()+"/" + IIdComboBox.Text.ToString().Trim() + "/"); }

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  • How can I add file locations to a database after they are uploaded using a Perl CGI script?

    - by Paul K
    I have a CGI program I have written using Perl. One of its functions is to upload pics to the server. All of it is working well, including adding all kinds of info to a MySQL db. My question is: How can I get the uploaded pic files location and names added to the db? I would rather that instead of changing the script to actually upload the pics to the db. I have heard horror stories of uploading binary files to databases. Since I am new to all of this, I am at a loss. Have tried doing some research and web searches for 3 weeks now with no luck. Any suggestions or answers would be greatly appreciated. I would really hate to have to manually add all the locations/names to the db. I am using: a Perl CGI script, MySQL db, Linux server and the files are being uploaded to the server. I AM NOT looking to add the actual files to the db. Just their location(s).

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  • Hash Tables - Java

    - by Antony
    Am about to do a homework, and i need to store quite a lot of information (Dictionary) in a data structure of my choice. I heard people in my classroom saying hash-tables are the way to go. How come?

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  • Stop overlooking minor details

    - by Mark Lubin
    Compared to most people on this site I am admittedly a novice. I wanted to get some advice from the pros on how to avoid making stupid errors in your code. Is there anyone else who had the problem when they were first starting out of missing some detail that causes big problems? Are there any habits or behaviors that helped you over come this.

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