for-loop

问题 So, I`m trying to write a function that removes the negative elements of a list without using .remove or .del. Just straight up for loops and while loops. I don`t understand why my code doesn`t work. Any assistance would be much appreciated. def rmNegatives(L): subscript = 0 for num in L: if num < 0: L = L[:subscript] + L[subscript:] subscript += 1 return L 回答1: A note to your code: L = L[:subscript] + L[subscript:] does not change your list. For example >>> l = [1,2,3,4] >>> l[:2] + l[2:] [1

问题 I have a vector: std::vector<int> vec = {1, 2, 3}; And I want to make a reverse for loop. It works, when I write: for(int i = vec.size() - 1; i >= 0; --i) { std::cout << i << std::endl; // 2, 1, 0 } But I get a very large number (like 18446744073709223794) if I write: for(size_t i = vec.size() - 1; i >= 0; --i) { std::cout << i << std::endl; } But they both work when I write: for(int i = 0; i < vec.size() - 1; ++i) { std::cout << i << std::endl; // 1, 2, 3 } // Or for(size_t i = 0; i < vec

问题 I have a vector: std::vector<int> vec = {1, 2, 3}; And I want to make a reverse for loop. It works, when I write: for(int i = vec.size() - 1; i >= 0; --i) { std::cout << i << std::endl; // 2, 1, 0 } But I get a very large number (like 18446744073709223794) if I write: for(size_t i = vec.size() - 1; i >= 0; --i) { std::cout << i << std::endl; } But they both work when I write: for(int i = 0; i < vec.size() - 1; ++i) { std::cout << i << std::endl; // 1, 2, 3 } // Or for(size_t i = 0; i < vec

问题 I am quite new to manipulating elements in the DOM in JS so I am creating a simple to do list to get more comfortable and where I can add items using the input and remove items by clicking on the list item. ALthough this may not be best practice and limitting I am just wanting to use create and remove elements rather than using objects or classes until I get more familar, also using plain/vanilla js so please keep this in mind when answering. I am trying to add a click event which removes the

问题 Is it possible to create a python for-loop with a modulo operation? I have a ringbuffer in Python and I want to iterate the elements between the startPos and endPos indexes, where startPos can have a bigger value than endPos . In other programming languages, I would intuitively implement this with a modulo operator: int startPos = 6; int endPos = 2; int ringBufferSize = 8; for(int i = startPos, i != endPos, i = (i+1) % ringBufferSize) { print buffer.getElementAt(i); } Is there a way to do

问题 I am new to Rust . I need to create a vector before a for loop. Run for loop on it. Change the vector inside the for loop. Then Change the vector after the for loop. I tried the following code and tried to use immutable borrow but both did not work. fn main() { let mut vec1 = vec![4, 5]; vec1.push(6); for i in vec1 { if i % 2 == 0 { vec1.push(7); } } vec1.push(8); println!("vec1={:?}", vec1); } I expect to compile and change the vector inside and after the for loop. But it shows this error

问题 I have a twig template to display audio options (Auto play and Continuos play) as shown in the screen shot: Click to see the screen shot of the page The following is the code in my twig file. {{ audio_options_form}} renders the form with the checkboxes.I want to display the check boxes only once if {{ item.audio }} is true. Please let me know what changes should I make: <div id="textcontent"> {% set field = data|slice(2) %} {% set field = field|slice(0, -1) %} <div class="col-md-12"> <div

问题 I have a twig template to display audio options (Auto play and Continuos play) as shown in the screen shot: Click to see the screen shot of the page The following is the code in my twig file. {{ audio_options_form}} renders the form with the checkboxes.I want to display the check boxes only once if {{ item.audio }} is true. Please let me know what changes should I make: <div id="textcontent"> {% set field = data|slice(2) %} {% set field = field|slice(0, -1) %} <div class="col-md-12"> <div

问题 What's exactly the action scope of let in a for-loop in JavaScript? for (let i = 0; i < 3; i++) { let i = 4; console.log(i); } console.log(i); The external console.log throws an error: "Uncaught Reference Error: i is not defined" It proves i is in a block action scope, however, why doesn't the i defined in the for-loop throw any duplicate definition error? 回答1: The body of a for loop (with a let variable declaration) has two scopes (or LexicalEnvironments): one scope is the iteration

问题 I have two arrays A (len of 3.8million) and B (len of 20k). For the minimal example, lets take this case: A = np.array([1,1,2,3,3,3,4,5,6,7,8,8]) B = np.array([1,2,8]) Now I want the resulting array to be: C = np.array([3,3,3,4,5,6,7]) i.e. if any value in B is found in A , remove it from A , if not keep it. I would like to know if there is any way to do it without a for loop because it is a lengthy array and so it takes long time to loop. 回答1: Using searchsorted With sorted B , we can use