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• Removing groups of similar records in MySQL query

  - by user1182155

  I'm trying to wrap my head around this... (it may be simple, been a long day!) I have a database with sometimes multiple similar records... ie. Apples 2008-09-03 Apples 2012-01-01 Apples 2013-10-24 Oranges 2012-01-04 What I need to do is do a query that will show only records that haven't been updated today... So in this case, since Apples has an entry that was updated today, none of the records for the Apples should appear in the results. Oranges should be the only record it returns. I have a query similar to this... SELECT fruit FROM fruitnames where date < CURDATE() Which works to remove the record that was updated today... But it keeps the other records for Apples (obviously)... How would I remove those results as well?

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• Fastest way to find the rotation of a vector

  - by kriss

  I have two 2D vectors, say u and v, defined by cartesian coordinates. Imagine that vectors are needles of a clock. I'm looking for the fastest way to find out, using python, if v is after or before u (or in other words find out in wich half plane is v, regarding to position of u). For the purpose of the problem if vectors are aligned answer should be before. It seems easy using some trigonometry, but I believe there should be a faster way using coordinates only. My test case: def after(u, v): """code here""" after((4,2), (6, 1)) : True after((4,2), (3, 3)) : False after((4,2), (2, 1)) : False after((4,2), (3, -3)) : True after((4,2), (-2, -5)) : True after((4,2), (-4, -2)) : False

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• mysql query to concat information from 3 tables - getting incorrect result count

  - by iPfaffy

  I have 3 tables in my database. ab_contacts id first_name last_name addressbook_id ab_addressbooks name id co_comments id link_id comment I'd like to create a query that will let me select all the contacts and comments related to them in a given addressbook. To select all the people in a given addressbook, I can use: select count(*) from ab_contacts where addressbook_id = '50'; This returns 8152 people. However, when I run my query: select ab_contacts.first_name, ab_contacts.last_name, ab_contacts.email, ab_addressbooks.name, co_comments.comments from ab_contacts JOIN ab_addressbooks ON (ab_contacts.addressbook_id = ab_addressbooks.id) JOIN co_comments ON (ab_contacts.id = co_comments.link_id) WHERE ab_contacts.addressbook_id = '50';` the format works, but I only get 1045 results. I'm sure there is something I am missing, but I cannot figure it out. Any help would be greatly appreciated.

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• How to custom query using ORM in Fuelphp?

  - by viyancs

  I have a problem when I want to query table using ORM ,example I have article table with field id,author,text. My code like this : // Single where $article = Model_Article::find()->where('id', 4); print_r($article); that't code will be fetch all field on table article, it's like select * from article where id = 4 Try Possibility $article = Model_Article::find(null, array('id','title'))->where('id', 3); the response is object(Orm\Query)#89 (14) { ["model":protected]=> string(10) "Model_Article" ["connection":protected]=> NULL ["view":protected]=> NULL ["alias":protected]=> string(2) "t0" ["relations":protected]=> array(0) { } ["joins":protected]=> array(0) { } ["select":protected]=> array(1) { ["t0_c0"]=> string(5) "t0.id" } ["limit":protected]=> NULL ["offset":protected]=> NULL ["rows_limit":protected]=> NULL ["rows_offset":protected]=> NULL ["where":protected]=> array(1) { [0]=> array(2) { [0]=> string(9) "and_where" [1]=> array(3) { [0]=> string(5) "t0.id" [1]=> string(1) "=" [2]=> int(3) } } } ["order_by":protected]=> array(0) { } ["values":protected]=> array(0) { } } that's is not return id or title field. but when i'm try by adding get_one() method $article = Model_Article::find(null, array('id','title'))->where('id', 3)->get_one(); id is return , but title is not and another field, i don't know why ? Reference ORM Discussion FuelPHP it's say ORM currently will be select all column, no plans to change that at the moment. My Goal I want to query in orm like this select id,owner from article where id = 4 it's will be return only id & owner, how i can get that using orm ?

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• Initializing a C++ vector to random values... fast

  - by Flamewires

  Hey, id like to make this as fast as possible because it gets called A LOT in a program i'm writing, so is there any faster way to initialize a C++ vector to random values than: double range;//set to the range of a particular function i want to evaluate. std::vector<double> x(30, 0.0); for (int i=0;i<x.size();i++) { x.at(i) = (rand()/(double)RAND_MAX)*range; } EDIT:Fixed x's initializer.

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• Controlling read and write access width to memory mapped registers in C

  - by srking

  I'm using and x86 based core to manipulate a 32-bit memory mapped register. My hardware behaves correctly only if the CPU generates 32-bit wide reads and writes to this register. The register is aligned on a 32-bit address and is not addressable at byte granularity. What can I do to guarantee that my C (or C99) compiler will only generate full 32-bit wide reads and writes in all cases? For example, if I do a read-modify-write operation like this: volatile uint32_t* p_reg = 0xCAFE0000; *p_reg |= 0x01; I don't want the compiler to get smart about the fact that only the bottom byte changes and generate 8-bit wide read/writes. Since the machine code is often more dense for 8-bit operations on x86, I'm afraid of unwanted optimizations. Disabling optimizations in general is not an option.

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• How computer multiplies 2 numbers?

  - by ckv

  How does a computer perform a multiplication on 2 numbers say 100 * 55. My guess was that the computer did repeated addition to achieve multiplication. Of course this could be the case for integer numbers. However for floating point numbers there must be some other logic. Note: This was asked in an interview.

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• How can I improve the below query?

  - by Newbie

  I have the following input. INPUT: TableA ID Sentences --- ---------- 1 I am a student 2 Have a nice time guys! What I need to do is to extract the words from the sentence(s) and insert each individual word in another table OUTPUT: SentenceID WordOccurance Word ---------- ------------ ----- 1 1 I 1 2 am 1 3 a 1 4 student 2 1 Have 2 2 a 2 3 nice 2 4 time 2 5 guys! I was able to get the answer by using the below query ;With numCTE As ( Select rn = 1 Union all Select rn+1 from numCTE where rn<1000) select SentenceID=id, WordOccurance=row_number()over(partition by TableA.ID order by rn), Word = substring(' '+sentences+' ', rn+1, charindex(' ',' '+sentences+' ', rn+1)-rn-1) from TableA join numCTE on rn <= len(' '+sentences+' ') where substring(' '+sentences+' ', rn,1) = ' ' order by id, rn How can I improve this query of mine.? Basically I am looking for a better solution than the one presented Thanks

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• SQL query to select distinct record with 2 or more repetition in another field

  - by kyohiros

  So I have this table of book orders, it contains 2 columns, one is the order ID(primary key) and another is the ID of the book that the customer ordered. For example: | OrderID | BookID | | 0001 | B002 | | 0002 | B005 | | 0003 | B002 | | 0004 | B003 | | 0005 | B005 | | 0006 | B002 | | 0007 | B002 | What I want is to get the IDs of the books that got 2 or more purchases/orders, for example if I run the SQL query against the above data, I would get this as the result: | BookID | | B002 | | B005 | I don't know if this can be archived in SQL or I have to built a simpler statement and repetitive run the query against all the records in another language. I need some help and thanks for reading my question.

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• SQL server 2005 query not running

  - by Aayushi

  Hi, Before posting this question, I have tried so many things but that was not helpful for me. I want to rename the column of table at sql server 2005, following query I have run at sql server2005: 1) ALTER TABLE Details RENAME COLUMN AccountID TO UID; but it gives me the error: Incorrect syntax near the keyword 'COLUMN'. 2)I have added one new column in the table by query: ALTER TABLE Details ADD BID uniqueidentifier; and then I want to set the coulmn property to not null . How can i do that? Thanks in advance AS

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• How to make if-elif-else statement in python more space-saving?

  - by Neverland

  I have a lot of if-elif-else statements in my code if message == '0' or message == '3' or message == '5' or message == '7': ... elif message == '1' or message == '2' or message == '4' or message == '6' or message == '8': ... else: ... Is it possible to format this in a more space-saving way? I tried it this way: if message == '0' or '3' or '5' or '7': ... elif message == '1' or '2' or '4' or '6' or '8': ... else: ... But without success.

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• C++ DWORD* to BYTE*

  - by NomeSkavinski

  My issue, i am trying to convert and array of dynamic memory of type DWORD to a BYTE. Fair enough i can for loop through this and convert the DWORD into a BYTE per entry. But is their a faster way to do this? to take a pointer to DWORD data and convert the whole piece of data into a pointer to BYTE data? such as using a memcpy operation? I feel this is not possible, im not requesting an answer just an experienced opinion on my approach, as i have tried testing both approaches but seem to fail getting to a solution on my second solution. Thanks for any input, again no answers just a point in the right direction. Nor is this a homework question, i felt that had to be mentioned.

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• Creating objects makes the VM faster?

  - by Sudhir Jonathan

  Look at this piece of code: MessageParser parser = new MessageParser(); for (int i = 0; i < 10000; i++) { parser.parse(plainMessage, user); } For some reason, it runs SLOWER (by about 100ms) than for (int i = 0; i < 10000; i++) { MessageParser parser = new MessageParser(); parser.parse(plainMessage, user); } Any ideas why? The tests were repeated a lot of times, so it wasn't just random. How could creating an object 10000 times be faster than creating it once?

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• Composite primary keys in N-M relation or not?

  - by BerggreenDK

  Lets say we have 3 tables (actually I have 2 at the moment, but this example might illustrate the thought better): [Person] ID: int, primary key Name: nvarchar(xx) [Group] ID: int, primary key Name: nvarchar(xx) [Role] ID: int, primary key Name: nvarchar(xx) [PersonGroupRole] Person_ID: int, PRIMARY COMPOSITE OR NOT? Group_ID: int, PRIMARY COMPOSITE OR NOT? Role_ID: int, PRIMARY COMPOSITE OR NOT? Should any of the 3 ID's in the relation PersonGroupRole be marked as PRIMARY key or should they all 3 be combined into one composite?? whats the real benefit of doing it or not? I can join anyways as far as I know, so Person JOIN PersonGroupRole JOIN Group gives me which persons are in which Groups etc. I will be using LINQ/C#/.NET on top of SQL-express and SQL-server, so if there is any reasons regarding language/SQL that might make the choice more clear, thats the platform I ask about. Looking forward to see what answers pops up, as I have thought of these primary keys/indexes many times when making combined ones.

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• Query to update rowNum

  - by BrokeMyLegBiking

  Can anyone help me write this query more efficiently? I have a table that captures TCP traffic, and I'd like to update a column called RowNumForFlow which is simly the sequential number of the IP packet in that flow. The code below works fine, but it is slow. declare @FlowID int declare @LastRowNumInFlow int declare @counter1 int set @counter1 = 0 while (@counter1 < 1) BEGIN set @counter1 = @counter1 + 1 -- 1) select top 1 @FlowID = t.FlowID from Traffic t where t.RowNumInFlow is null if (@FlowID is null) break -- 2) set @LastRowNumInFlow = null select top 1 @LastRowNumInFlow = RowNumInFlow from Traffic where FlowID=@FlowID and RowNumInFlow is not null order by ID desc if @LastRowNumInFlow is null set @LastRowNumInFlow = 1 else set @LastRowNumInFlow = @LastRowNumInFlow + 1 update Traffic set RowNumInFlow = @LastRowNumInFlow where ID = (select top 1 ID from Traffic where flowid = @FlowID and RowNumInFlow is null) END Example table values after query has run: ID FlowID RowNumInFlow 448923 44 1 448924 44 2 448988 44 3 448989 44 4 448990 44 5 448991 44 6 448992 44 7 448993 44 8 448995 44 9 448996 44 10 449065 44 11 449063 45 1 449170 45 2 449171 45 3 449172 45 4 449187 45 5

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• Java - Optimize finding a string in a list

  - by Mark

  I have an ArrayList of objects where each object contains a string 'word' and a date. I need to check to see if the date has passed for a list of 500 words. The ArrayList could contain up to a million words and dates. The dates I store as integers, so the problem I have is attempting to find the word I am looking for in the ArrayList. Is there a way to make this faster? In python I have a dict and mWords['foo'] is a simple lookup without looping through the whole 1 million items in the mWords array. Is there something like this in java? for (int i = 0; i < mWords.size(); i++) { if ( word == mWords.get(i).word ) { mLastFindIndex = i; return mWords.get(i); } }

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• Thin down jQuery

  - by Taylor Satula

  Hi, I have been optimizing my website but the one problem that stands in my way is all the jQuery functions that I do not use. The only ones that I use are for a smooth page scroller. It just seems like such a waste of download time. My question is: Is there any script or program that will remove the jQuery code that I do not need and leave the 1 or 2 functions that I do need.

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• Calculating Growth-Rates by applying log-differences

  - by mropa

  I am trying to transform my data.frame by calculating the log-differences of each column and controlling for the rows id. So basically I like to calculate the growth rates for each id's variable. So here is a random df with an id column, a time period colum p and three variable columns: df <- data.frame (id = c("a","a","a","c","c","d","d","d","d","d"), p = c(1,2,3,1,2,1,2,3,4,5), var1 = rnorm(10, 5), var2 = rnorm(10, 5), var3 = rnorm(10, 5) ) df id p var1 var2 var3 1 a 1 5.375797 4.110324 5.773473 2 a 2 4.574700 6.541862 6.116153 3 a 3 3.029428 4.931924 5.631847 4 c 1 5.375855 4.181034 5.756510 5 c 2 5.067131 6.053009 6.746442 6 d 1 3.846438 4.515268 6.920389 7 d 2 4.910792 5.525340 4.625942 8 d 3 6.410238 5.138040 7.404533 9 d 4 4.637469 3.522542 3.661668 10 d 5 5.519138 4.599829 5.566892 Now I have written a function which does exactly what I want BUT I had to take a detour which is possibly unnecessary and can be removed. However, somehow I am not able to locate the shortcut. Here is the function and the output for the posted data frame: fct.logDiff <- function (df) { df.log <- dlply (df, "code", function(x) data.frame (p = x$p, log(x[, -c(1,2)]))) list.nalog <- llply (df.log, function(x) data.frame (p = x$p, rbind(NA, sapply(x[,-1], diff)))) ldply (list.nalog, data.frame) } fct.logDiff(df) id p var1 var2 var3 1 a 1 NA NA NA 2 a 2 -0.16136569 0.46472004 0.05765945 3 a 3 -0.41216720 -0.28249264 -0.08249587 4 c 1 NA NA NA 5 c 2 -0.05914281 0.36999681 0.15868378 6 d 1 NA NA NA 7 d 2 0.24428771 0.20188025 -0.40279188 8 d 3 0.26646102 -0.07267311 0.47041227 9 d 4 -0.32372771 -0.37748866 -0.70417351 10 d 5 0.17405309 0.26683625 0.41891802 The trouble is due to the added NA-rows. I don't want to collapse the frame and reduce it, which would be automatically done by the diff() function. So I had 10 rows in my original frame and am keeping the same amount of rows after the transformation. In order to keep the same length I had to add some NAs. I have taken a detour by transforming the data.frame into a list, add the NAs, and afterwards transform the list back into a data.frame. That looks tedious. Any ideas to avoid the data.frame-list-data.frame class transformation and optimize the function?

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• Visual C++ 9 compiler options to make the program run faster

  - by John Williams

  I have built an open-source application from the source code. Unfortunately, the original executable runs significantly faster. I tried to enable few compiler optimizations, but the result wasn't satisfactory enough. What else do I need to make in Visual Studio 2008 to increase the executable performance? Thanks!

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• JavaScript Optimisation

  - by Jayie

  I am using JavaScript to work out all the combinations of badminton doubles matches from a given list of players. Each player teams up with everyone else. EG. If I have the following players a, b, c & d. Their combinations can be: a & b V c & d a & c V b & d a & d V b & c I am using the code below, which I wrote to do the job, but it's a little inefficient. It loops through the PLAYERS array 4 times finding every single combination (including impossible ones). It then sorts the game out into alphabetical order and stores it in the GAMES array if it doesn't already exist. I can then use the first half of the GAMES array to list all game combinations. The trouble is if I have any more than 8 players it runs really slowly because the combination growth is exponential. Does anyone know a better way or algorithm I could use? The more I think about it the more my brain hurts! var PLAYERS = ["a", "b", "c", "d", "e", "f", "g"]; var GAMES = []; var p1, p2, p3, p4, i1, i2, i3, i4, entry, found, i; var pos = 0; var TEAM1 = []; var TEAM2 = []; // loop through players 4 times to get all combinations for (i1 = 0; i1 < PLAYERS.length; i1++) { p1 = PLAYERS[i1]; for (i2 = 0; i2 < PLAYERS.length; i2++) { p2 = PLAYERS[i2]; for (i3 = 0; i3 < PLAYERS.length; i3++) { p3 = PLAYERS[i3]; for (i4 = 0; i4 < PLAYERS.length; i4++) { p4 = PLAYERS[i4]; if ((p1 != p2 && p1 != p3 && p1 != p4) && (p2 != p1 && p2 != p3 && p2 != p4) && (p3 != p1 && p3 != p2 && p3 != p4) && (p4 != p1 && p4 != p2 && p4 != p3)) { // sort teams into alphabetical order (so we can compare them easily later) TEAM1[0] = p1; TEAM1[1] = p2; TEAM2[0] = p3; TEAM2[1] = p4; TEAM1.sort(); TEAM2.sort(); // work out the game and search the array to see if it already exists entry = TEAM1[0] + " & " + TEAM1[1] + " v " + TEAM2[0] + " & " + TEAM2[1]; found = false; for (i=0; i < GAMES.length; i++) { if (entry == GAMES[i]) found = true; } // if the game is unique then store it if (!found) { GAMES[pos] = entry; document.write((pos+1) + ": " + GAMES[pos] + "<br>"); pos++; } } } } } } Thanks in advance. Jason.

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• Whether to put method code in a VB.Net data storage class, or put it in a separate class?

  - by Alan K

  TLDR summary: (a) Should I include (lengthy) method code in classes which may spawn multiple objects at runtime, (b) does doing so cause memory usage bloat, (c) if so should I "outsource" the code to a class that is loaded only once and have the class methods call that, or alternatively (d) does the code get loaded only once with the object definition anyway and I'm worrying about nothing? ........ I don't know whether there's a good answer to this but if there is I haven't found it yet by searching in the usual places. In my VB.Net (2010 if it matters) WinForms project I have about a dozen or so class objects in an object model. Some of these are pretty simple and do little more than act as data storage repositories. The ones further up the object model, however, have an increasing number of methods. There can be a significant number of higher level objects in use though the exact number will be runtime dependent so I can't be more precise than that. As I was writing the method code for one of the top level ones I noticed that it was starting to get quite lengthy. Memory optimisation is something of a lost art given how much memory the average PC has these days but I don't want to make my application a resource hog. So my questions for anyone who knows .Net way better than I do (of which there will be many) are: Is the code loaded into memory with each instance of the class that's created? Alternatively is it loaded only once with the definition of the class, and all derived objects just refer to that definition? (I'm not really sure how that could be possible given that, for example, event handlers can be assigned dynamically, but no harm asking.) If the answer to the first one is yes, would it be more efficient to write the code in a "utility" object which is loaded only once and called from the real class' methods? Any thoughts appreciated.

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• How to get REALLY fast python over a simple loop

  - by totallymike

  I'm working on a spoj problem, INTEST. The goal is to specify the number of test cases (n) and a divisor (k), then feed your program n numbers. The program will accept each number on a newline of stdin and after receiving the nth number, will tell you how many were divisible by k. The only challenge in this problem is getting your code to be FAST because it k can be anything up to 10^7 and the test cases can be as high as 10^9. I'm trying to write it in python and having trouble speeding it up. Any ideas? import sys first_in = raw_input() thing = first_in.split() n = int(thing[0]) k = int(thing[1]) total = 0 i = 0 for line in sys.stdin: t = int(line) if t % k == 0: total += 1 print total

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• Where does the compiler store methods for C++ classes?

  - by Mashmagar

  This is more a curiosity than anything else... Suppose I have a C++ class Kitty as follows: class Kitty { void Meow() { //Do stuff } } Does the compiler place the code for Meow() in every instance of Kitty? Obviously repeating the same code everywhere requires more memory. But on the other hand, branching to a relative location in nearby memory requires fewer assembly instructions than branching to an absolute location in memory on modern processors, so this is potentially faster. I suppose this is an implementation detail, so different compilers may perform differently. Keep in mind, I'm not considering static or virtual methods here.

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• I'm doing a lot of lists and dictionary sorting...and this is causing memory errors in Python websit

  - by alex

  I retrieved data from the log table in my database. Then I started finding unique users, comparing/sorting lists, etc. In the end I got down to this. stats = {'2010-03-19': {'date': '2010-03-19', 'unique_users': 312, 'queries': 1465}, '2010-03-18': {'date': '2010-03-18', 'unique_users': 329, 'queries': 1659}, '2010-03-17': {'date': '2010-03-17', 'unique_users': 379, 'queries': 1845}, '2010-03-16': {'date': '2010-03-16', 'unique_users': 434, 'queries': 2336}, '2010-03-15': {'date': '2010-03-15', 'unique_users': 390, 'queries': 2138}, '2010-03-14': {'date': '2010-03-14', 'unique_users': 460, 'queries': 2221}, '2010-03-13': {'date': '2010-03-13', 'unique_users': 507, 'queries': 2242}, '2010-03-12': {'date': '2010-03-12', 'unique_users': 629, 'queries': 3523}, '2010-03-11': {'date': '2010-03-11', 'unique_users': 811, 'queries': 4274}, '2010-03-10': {'date': '2010-03-10', 'unique_users': 171, 'queries': 1297}, '2010-03-26': {'date': '2010-03-26', 'unique_users': 299, 'queries': 1617}, '2010-03-27': {'date': '2010-03-27', 'unique_users': 323, 'queries': 1310}, '2010-03-24': {'date': '2010-03-24', 'unique_users': 352, 'queries': 2112}, '2010-03-25': {'date': '2010-03-25', 'unique_users': 330, 'queries': 1290}, '2010-03-22': {'date': '2010-03-22', 'unique_users': 329, 'queries': 1798}, '2010-03-23': {'date': '2010-03-23', 'unique_users': 329, 'queries': 1857}, '2010-03-20': {'date': '2010-03-20', 'unique_users': 368, 'queries': 1693}, '2010-03-21': {'date': '2010-03-21', 'unique_users': 329, 'queries': 1511}, '2010-03-29': {'date': '2010-03-29', 'unique_users': 325, 'queries': 1718}, '2010-03-28': {'date': '2010-03-28', 'unique_users': 340, 'queries': 1815}, '2010-03-30': {'date': '2010-03-30', 'unique_users': 329, 'queries': 1891}} It's not a big dictionary. But when I try to do one last thing...it craps out on me. for k, v in stats: mylist.append(v) too many values to unpack What the heck does that mean??? TOO MANY VALUES TO UNPACK.

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• Execute a method less times possible - PHP

  - by serhio

  I have a site in multiple languages. I have a method that returns me the today currencies in a array. I display that currencies in a table then. // --- en/index.php <?php include_once "../exchangeRates.php"; $currencies = ReadExchangeRates(); // --- fr/index.php <?php include_once "../exchangeRates.php"; $currencies = ReadExchangeRates(); ... // somewhere in the page <td><?php echo $currencies["eur"]["today"]; ?></td> So, every time I load, en/ or fr/ or other language, I request the exchange rates from a external site. Can I optimize this behavior (reading once per day or session)? maybe to store a global variable and check the update date?

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