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• Combining entries, filtering of Python dictionaries

  - by matt

  I have two large lists that are filled with dictionaries. I need to combine the entries if a value from dict2==dict1 and place the newly combined matches somewhere else. I'm having trouble explaining it. List one contains: {'keyword':value, 'keyword2':value2} List two: {'keyword2':value2, 'keyword3':value3} I want a new list with dictionaries including keyword1, keyword2, and keyword3 if both lists share the same 'keyword2' value. What's the best way to do this? When I try, I only come up with tons of nested for loops. Thanks

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• Show me some cool python list comprehensions

  - by christangrant

  One of the major strengths of python and a few other (functional) programming languages are the list comprehension. They allow programmers to write complex expressions in 1 line. They may be confusing at first but if one gets used to the syntax, it is much better than nested complicated for loops. With that said, please share with me some of the coolest uses of list comprehensions. (By cool, I just mean useful) It could be for some programming contest, or a production system. For example: To do the transpose of a matrix mat >>> mat = [ ... [1, 2, 3], ... [4, 5, 6], ... [7, 8, 9], ... ] >>> [[row[i] for row in mat] for i in [0, 1, 2]] [[1, 4, 7], [2, 5, 8], [3, 6, 9]] Please include a description of the expression and where it was used (if possible).

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• Selecting a value from multiple dictionaries inside an enumeration

  - by johaanfaust

  If I have an enumeration of dictionaries IEnumerable<IDictionary<string, float>> enumeration can I perform a Linq query on it so that I can select by a value from each dictionary in the enumeration using the same key? I can do this in a loop: float f; foreach (var dictionary in enumeration) { if (dictionary.TryGetValue("some key", out f)) { Console.WriteLine(f); } } (The eventual plan is to compare the performance of the query verses the equivalent nested looping statements (the enumeration itself is formed from either another query or an equivalent set of loops).)

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• ask. help me to compare two array of integers and the order does not matter.

  - by stdnoit

  [Example] <1 2 3 4 = <3 1 2 4 <1 2 3 4 != <3 4 1 1 and ummm it is in java. cant use hashmap table or anything just pure without library. I know there are two ways. 1. sort them and compare the array index by index 2. use two for loops and compare the outer index with the inner index. ( i have been trying with this but still not working) for(int i = 0; i < n; i++) { for(int j = 0; j < n; j++) { if(a[i] != a[j] && j == n) return false; } } return true; anything wrong with the code ? thanks

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• conditional while loop in php?

  - by julio

  I'm pretty sure there's an obvious answer for this-- hoping someone can help me-- I need to do a PHP while loop, but only if a variable is true. And I can't really put the while loop in an "if" statement, which seems like the obvious thing to do, since the code block is huge and it would be ugly and confusing. Do I need to break out the code in the loop into a function, or is there an easier way to deal with this? Here's the basic idea: if(condition){ while(another_condition){ //huge block of code loops many times } } else { // huge block of code runs once } I want the huge block of code to execute regardless of the state of the condition variable-- but only to execute once if condition is false, and execute for as long as another_condition is true if condition is true. Hope that's clear! The following code doesn't work, but gives an idea of what I want to accomplish: if(condition){ while(another_condition){ } // huge block of code if (condition){ } } // closes the while loop-- obviously throws an error though! thanks in advance.

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• Replace text in code with counting numbers

  - by Gpx

  Hi, due to testing and time measuring i have to write some kind of log into existing c# winforms code in Visual Studio 2010. I want to hold the changes and the work very small so my question is about replacing text in my call by counting numbers. Lets say i want to past a line like Log.WriteLine(position) many times in the code and then replace "position" with numbers starting from 1 to n in on turn. I cant use a counter in this case because of many loops i don´t get the right position. Thanks for any suggestions, Gpx

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• Query Execution Plan - When is the Where clause executed?

  - by Alex

  I have a query like this (created by LINQ): SELECT [t0].[Id], [t0].[CreationDate], [t0].[CreatorId] FROM [dbo].[DataFTS]('test', 100) AS [t0] WHERE [t0].[CreatorId] = 1 ORDER BY [t0].[RANK] DataFTS is a full-text search table valued function. The query execution plan looks like this: SELECT (0%) - Sort (23%) - Nested Loops (Inner Join) (1%) - Sort (Top N Sort) (25%) - Stream Aggregate (0%) - Stream Aggregate (0%) - Compute Scalar (0%) - Table Valued Function (FullTextMatch) (13%) | | - Clustered Index Seek (38%) Does this mean that the WHERE clause ([CreatorId] = 1) is executed prior to the TVF ( full text search) or after the full text search? Thank you.

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• Expectation values in MATLAB

  - by Bowler

  I have a 3D data set representing a grid of photosensors which unfortunately were not steady during use. I have estimated the pdf for the motion of the detector and I want to find the expectation value for each sensor. As I don't want to reflect my pdf (i.e. I want f(t) not f(t-tau)) I don't think I can use the matlab convolve function. Is there a function that will do what I want. I guess f I've found movavg but it seems to do something else. Also, as I'm faily new to matlab, from C, I tend to use for loops which I'm aware is not the way to use Matlab. Is there an easy way to convert my 1-D pdf to a 3D matrix that will only operate in one axis (z in this case). Something like repmat(i, j, pdf)

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• Best practice to avoid InvalidOperationException: Collection was modified?

  - by Roflcoptr

  Very often I need something like that: foreach (Line line in lines) { if (line.FullfilsCertainConditions()) { lines.Remove(line) } } This does not work, because I always get a InvalidOperationException because the Enumerator was changed during the loop. So I changed all my loops of this kind to the following: List<Line> remove = new List<Line>(); foreach (Line line in lines) { if (line.FullfilsCertainConditions()) { remove.Add(line) } } foreach (Line line in remove) { { lines.Remove(line); } I'm not sure if this is really the best way since in the worst case I have to iterate 2 times over the original list and so it needs time 2n instead of n. Is there a better way to do this?

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• Stopping an if clause along with the whole PHP script, but not HTML

  - by user626816

  Hello there, I've been having this problem for around an hour, and have searched the internet for answers. I've checked the PHP documentation, looked around, Googled, nothing. Anyways, my problem is that after I try to validate something (and it's wrong), if I use exit; it will also stop the HTML after. Here's what I'm talking about: if ($_POST['exampleEmail'] == "") { echo "Please enter an e-mail."; //Now I want only the PHP script to stop, however... exit; //If I use exit, then the HTML after this script (footer) doesn't show. } If anyone can help, please do. I've tried using break, but to no avail, since it's only for loops and switches. If there is a better/more correct (or simply correct if this is the wrong way), please share. I've had this problem in the past, and I just used exit then. Thanks.

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• Is it a good idea to apply some basic macros to simplify code in a large project?

  - by DoctorT

  I've been working on a foundational c++ library for some time now, and there are a variety of ideas I've had that could really simplify the code writing and managing process. One of these is the concept of introducing some macros to help simplify statements that appear very often, but are a bit more complicated than should be necessary. For example, I've come up with this basic macro to simplify the most common type of for loop: #define loop(v,n) for(unsigned long v=0; v<n; ++v) This would enable you to replace those clunky for loops you see so much of: for (int i = 0, i < max_things; i++) With something much easier to write, and even slightly more efficient: loop (i, max_things) Is it a good idea to use conventions like this? Are there any problems you might run into with different types of compilers? Would it just be too confusing for someone unfamiliar with the macro(s)?

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• How SqlDataAdapter works internally?

  - by tigrou

  I wonder how SqlDataAdapter works internally, especially when using UpdateCommand for updating a huge DataTable (since it's usually a lot faster that just sending sql statements from a loop). Here is some idea I have in mind : It creates a prepared sql statement (using SqlCommand.Prepare()) with CommandText filled and sql parameters initialized with correct sql types. Then, it loops on datarows that need to be updated, and for each record, it updates parameters values, and call SqlCommand.ExecuteNonQuery(). It creates a bunch of SqlCommand objects with everything filled inside (CommandText and sql parameters). Several SqlCommands at once are then batched to the server (depending of UpdateBatchSize). It uses some special, low level or undocumented sql driver instructions that allow to perform an update on several rows in a effecient way (rows to update would need to be provided using a special data format and a the same sql query (UpdateCommand here) would be executed against each of these rows).

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• Can a shell loop unzip all the files in a directory?

  - by helpwithshell

  I've seen loops to unzip all zip files in a directory. However, before I run this, I would rather make sure what I'm about to run will work right: for i in dir; do cd $i; unzip '*.zip'; rm -rf *.zip; cd ..; done Basically I want it to look at the output of "dir" see all the folders, for each directory cd into it, unzip all the zip archives, then remove them, then cd back and do it again until there are no more. Is this something I should do in a single command or should I consider doing this in Perl?

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• python input for itertools.product

  - by user364249

  Looking for a way to simulate nested loops (or a cartesian product) i came across the itertools.product function. i need a function or piece of code that receive a list of integers as input and returns a specific generator. example: input = [3,2,4] - gen = product(xrange(3),xrange(2),xrange(4)) or input = [2,4,5,6] - gen = product(xrange(2),xrange(4),xrange(5),xrange(6)) as the size of the lists varies i am very confused in how to do that without the need of a lot of precoding based on a crazy amount of ifs and the size of the list. also is there a difference in calling product(range(3)) or product(xrange(3))?

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• How do I find all the datetimes that happen on a particular date in ruby?

  - by Angela

  I have a method which goes through each day of the week: def dates_week(d, delim) "<tr>" + (d.beginning_of_week...(d.beginning_of_week+5)).map do |day| "<#{delim}> #{yield(day)} </#{delim}>" end.join + "</tr>" end For each day of the week, I plug that as an arg into a method (or maybe a named_scope, haven't figured out which), that will then output the .count for :all the emails that have a :date_sent on that date. However, :date_sent is a date-timestamp, so I can't use == as I have below. def sent_emails_by_date(date) ContactEmail.find(:all, :conditions => "date_sent = '#{date}'" " ).count end How do I find all the emails that fall on the day for the date passed through from the method which loops through a week as shown above?

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• Loading XML with possible infinite tags

  - by Firstmate

  (I'm doing this in AS3, but I'm sure the answer could be given in psuedocode) Basically, I have a XML file similar to: <Main> <Event> <Name>Blah</Name> <Event> Name>Blah2</Name> <Event> <Name>Blah3</Name> ... </Event> </Event> </Event> </Main> Yeah, to some extent it's poor design. But the idea I'm going for is that any Event has the potential to compromise of other Events and this idea kinda loops. Any ideas on how to do this?

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• Solving C++ 'target of assignment not really an lvalue' errors

  - by Jason

  Given this code: void FrMemCopy(void *to, const void *from, size_t sz) { size_t sz8 = sz >> 3; size_t sz1 = sz - (sz8 << 3); while (sz8-- != 0) { *((double *)to)++ = *((double *)from)++; } while (sz1-- != 0) { *((char *)to)++ = *((char *)from)++; } } I am receiving target of assignment not really an lvalue warnings on the 2 lines inside the while loops. Can anyone break down those lines? a cast then an increment? What is a simplier way to write that? What does the error mean?

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• How to prevent users from typing incorrect inputs ?

  - by ZaZu

  Hello, I want the program to loop a scan function if the user types anything else other than numbers.. My code is : do{ printf("Enter rows\n"); scanf("%d",&row); }while(row>='a' && row<='z'); but this code doesnt work .. I keep getting an error when typing in a letter. I tried manipulating around it and the whole thing loops infinitely ... What am I doing wrong ? Please help thanks !

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• Constant embedded for loop condition optimization in C++ with gcc

  - by solinent

  Will a compiler optimize tihs: bool someCondition = someVeryTimeConsumingTask(/* ... */); for (int i=0; i<HUGE_INNER_LOOP; ++i) { if (someCondition) doCondition(i); else bacon(i); } into: bool someCondition = someVeryTimeConsumingTask(/* ... */); if (someCondition) for (int i=0; i<HUGE_INNER_LOOP; ++i) doCondition(i); else for (int i=0; i<HUGE_INNER_LOOP; ++i) bacon(i); someCondition is trivially constant within the for loop. This may seem obvious and that I should do this myself, but if you have more than one condition then you are dealing with permuatations of for loops, so the code would get quite a bit longer. I am deciding on whether to do it (I am already optimizing) or whether it will be a waste of my time.

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• When iterating over values, why does typeof(value) return "string" when value is a number? Javascrip

  - by Mark

  I'm using Google Chrome for this test: Contrary to intuition, the first loop alerts "string" 3 times, while the second loop alerts "number" 3 times. numarray = [1, 2, 3]; //for-each loop for(num in numarray) alert(typeof(num)); //standard loop for(i=0; i<numarray.length; i++) alert(typeof(numarray[i])); I was expecting both loops to alert "number" 3 times. How is the first loop implemented in Javascript? In other words, if the for-each is syntactic sugar, what is its equivalent using a standard loop? Also, is there some way to iterate over an object's namespace using a standard loop? I'm looking to touch every one of some object's methods and attributes using a loop of the second kind. I'm new to Javascript and any help is highly appreciated, thanks.

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• Failing faster when URL content is not found, howto

  - by Jam

  I have a thread pool that loops over a bunch of pages and checks to see if some string is there or not. If String is found, or not found response is near instant, however if server is offline or application is not running getting a rejection seems to take seconds How can I change my code to fail faster? for (Thread thread : pool) { thread.start(); } for (Thread thread : pool) { try { thread.join(); } catch (InterruptedException e) { e.printStackTrace(); } } Here is my run method @Override public void run() { for (Box b : boxes) { try { connection = new URL(b.getUrl()).openConnection(); scanner = new Scanner(connection.getInputStream()); scanner.useDelimiter("\\Z"); content = scanner.next(); if (content.equals("YES")) { } else { System.out.println("\tFAILED ON " + b.getName() + " BAD APPLICATION STATE"); } } catch (Exception ex) { System.out.println("\tFAILED ON " + b.getName() + " BAD APPLICATION STATE"); } } }

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• Finding the most similar numbers across multiple lists in Python

  - by new_sysadmin

  In Python, I have 3 lists of floating-point numbers (angles), in the range 0-360, and the lists are not the same length. I need to find the triplet (with 1 number from each list) in which the numbers are the closest. (It's highly unlikely that any of the numbers will be identical, since this is real-world data.) I was thinking of using a simple lowest-standard-deviation method to measure agreement, but I'm not sure of a good way to implement this. I could loop through each list, comparing the standard deviation of every possible combination using nested for loops, and have a temporary variable save the indices of the triplet that agrees the best, but I was wondering if anyone had a better or more elegant way to do something like this. Thanks!

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• java: communication between threads

  - by TRU7H

  I'm making a little java game in which I would have two threads (well as the FIRST step towards multithreading...), one for the logic and one for the drawing. So my question is: How can I make those two communicating which each other? Requirements: accessing variables and object from a another thread syncing them so they each complete a same number of "loops" in the same time. (the logic calculates and then the another one draws the results and the loop begins again...) So how is this achievable in java? Thanks in advance!

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• Print number series in java

  - by user1898282

  I have to print the series shown below in java: ***1*** **2*2** *3*3*3* 4*4*4*4 My current implementation is: public static void printSeries(int number,int numberOfCharsinEachLine){ String s="*"; for(int i=1;i<=number;i++){ int countOfs=(numberOfCharsinEachLine-(i)-(i-1))/2; if(countOfs<0){ System.out.println("Can't be done"); break; } for(int j=0;j<countOfs;j++){ System.out.print(s); } System.out.print(i); for(int k=1;k<i;k++){ System.out.print(s); System.out.print(i); } for(int j=0;j<countOfs;j++){ System.out.print(s); } System.out.println(); } } But there are lot of for loops, so I'm wondering whether this can be done in a better way or not?

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• Getting differences between collections in LINQ

  - by dotnetdev

  Hi, I have a collection of image paths, and a larger collection of Image objects (Which contain a path property). I have the code to check for any matching images, but if there are supposed to be four matching image paths (as that is how many are in the first collection), and there is less than this, how can I get the missing one without writing loops? List<string> ImagesToCheck = new List<string>() { "", "s", "ssdd" }; IEnumerable<HtmlImage> Images = manager.ActiveBrowser.Find.AllControls<HtmlImage>(); var v = from i in Images where ImagesToCheck.Any(x => x == i.Src) select i; if (v.Count() < 3) { } So I need to get the items which are not in the collection titled v, but are in ImagesToCheck. How could I do this with LINQ? Thanks

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