for-loop

问题 I'm a rookie hobbyist and I nest for loops when I write python, like so: dict = { key1: {subkey/value1: value2} ... keyn: {subkeyn/valuen: valuen+1} } for key in dict: for subkey/value in key: do it to it I'm aware of a "next" keyword that would accomplish the same goal in one line (I asked a question about how to use it but I didn't quite understand it). So to me, a nested for loop is much more readable. Why, then do people use "next"? I read somewhere that Python is a dynamically-typed and

问题 I have the following Python 2.7 code: listOfLists = [] for l1_index, l1 in enumerate(L1): list = [] for l2 in L2: for l3_index,l3 in enumerate(L3): if (L4[l2-1] == l3): value = L5[l2-1] * l1[l3_index] list.append(value) break listOfLists.append(list) with the L1,L2,L3,L4,L5 lists being: L1 = [[0.60, 0.95, 0.38, 1.02, 0.29, 0.43], [0.40, 0.09, 0.87, 0.85, 0.70, 0.46], [0.67, 0.91, 0.66, 0.79, 0.86, 0.06], [0.59, 1.81, 0.05, 1.88, 0.20, 0.48], [0.64, 0.34, 0.37, 1.39, 0.56, 0.27], [0.56, 0.34,

问题 ...if that is possible My task is to find the longest streak of continuous days a user participated in a game. Instead of writing an sql function, I chose to use the R's rle function, to get the longest streaks and then update my db table with the results. The (attached) dataframe is something like this: day user_id 2008/11/01 2001 2008/11/01 2002 2008/11/01 2003 2008/11/01 2004 2008/11/01 2005 2008/11/02 2001 2008/11/02 2005 2008/11/03 2001 2008/11/03 2003 2008/11/03 2004 2008/11/03 2005

问题 I am trying to do this but it's says Value of type 'AnyObject?' has no member 'Generator' So this is my code. let dataDictionary:NSDictionary = try NSJSONSerialization.JSONObjectWithData(responseObject as! NSData, options: NSJSONReadingOptions.MutableContainers) as! NSDictionary var customerArray = dataDictionary.valueForKey("kart") for js: NSDictionary in customerArray { let nameArray: NSArray = js.valueForKey("name") } What I am doing wrong.I didn't figure out.Thank you for your helps. 回答1:

问题 I am trying to do this but it's says Value of type 'AnyObject?' has no member 'Generator' So this is my code. let dataDictionary:NSDictionary = try NSJSONSerialization.JSONObjectWithData(responseObject as! NSData, options: NSJSONReadingOptions.MutableContainers) as! NSDictionary var customerArray = dataDictionary.valueForKey("kart") for js: NSDictionary in customerArray { let nameArray: NSArray = js.valueForKey("name") } What I am doing wrong.I didn't figure out.Thank you for your helps. 回答1:

问题 I am writing some code where I need to use two variables in a for loop. Does the below code seem alright? It does give me the expected result. for (loop_1 = offset,loop_2 = (offset + 2); loop_1 >= (offset - 190),loop_2 <= (190 + offset + 2); loop_1--,loop_2++) { if ( (*(uint8_t*)(in_payload + loop_1) == get_a1_byte(bitslip)) && ((*(uint8_t*)(in_payload + loop_2) == get_a2_byte(bitslip))) ) { a1_count++; } } But I am getting a compiler warning which says: file.c:499:73: warning: left-hand

问题 I have a for loop in Matlab, and all the code inside the for loop is enclosed in an if statement. For example : for p = 1:length(array) if array(p) == 1 %// Test positive for condition %// Generic code here that %// Only executes if p == 1 end; end; Is it faster to have test for equality using an if statement, and execute the interior code if true, or, to test for inequality and then use a continue statement, such as : for p = 1:length(array) if array(p) ~= 1 %// Test negative for condition

问题 I am just learning MATLAB and I find it hard to understand the performance factors of loops vs vectorized functions. In my previous question: Nested for loops extremely slow in MATLAB (preallocated) I realized that using a vectorized function vs. 4 nested loops made a 7x times difference in running time . In that example instead of looping through all dimensions of a 4 dimensional array and calculating median for each vector, it was much cleaner and faster to just call median(stack, n) where

问题 Is the C++ code below legal, or is there a problem with my compiler? The code was complied into a shared library using gcc version 4.4.6 20110731 (Red Hat 4.4.6-3) (GCC) and openMP and then called via R 2.15.2. int it=0; #pragma omp parallel sections shared(it) { #pragma omp section { std::cout<<"Entering section A"<<std::endl; for(it=0;it<10;it++) { std::cout<<"Iteration "<<it<<std::endl; } std::cout<<"Leaving section A with it="<<it<<std::endl; } #pragma omp section { std::cout<<"Entering

问题 I am using Python; and I need to iterate through JSON objects and retrieve nested values. A snippet of my data follows: "bills": [ { "url": "http:\/\/maplight.org\/us-congress\/bill\/110-hr-195\/233677", "jurisdiction": "us", "session": "110", "prefix": "H", "number": "195", "measure": "H.R. 195 (110\u003csup\u003eth\u003c\/sup\u003e)", "topic": "Seniors' Health Care Freedom Act of 2007", "last_update": "2011-08-29T20:47:44Z", "organizations": [ { "organization_id": "22973", "name": "National