slice | 易学教程

How to slice a id and grab a number?

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问题 I have a jQuery id like <div id="myid-page-top-0"> some stuff </div> I want to use jQuery to grab the "0" from the end of the #id . I have tried like $('div').slice(-1,0); But this doesn't work ? Any ideas ? 回答1: Instead of slice, which would only work if your id contains numbers 0-9, not if it is say 10 or 11, you should base it off of the dashes. Something like: var id = "myid-page-top-0"; alert(id.split("-")[3]); or in your code something like: var number = $('div').attr('id').split("-")[3

Golang 切片

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一个切片(slice) 是一个数组某个部分的引用。 1、切片初始化（1）、通过内置函数make初始化： slice := make([]Type,len,[cap]) []Type，某种类型的数组； Len 表示切片数据长度； Cap 表示切片容量，cap >= len，该参数可选，默认cap=len 例如： slice := make([]string,5) //初始化一个字符串类型的切片，长度和容量均为5 slice := make([]string,5,10) //初始化一个字符串类型的切片，长度为5，容量为10 （2）、通过现有数组来初始化 slice := arr[startIndex:endIndex] //startIndex,endIndex可选，startIndex默认为0，endIndex默认为arr长度，取得的数组下标是[startIndex:endIndex) 左闭右开区间例如： arr := […]string{"aaa","bbb","ccc","ddd"} slice := arr[1:4] //[1:4) 共3个元素创建一个切片 slice := arr[:4] //[0:4) 共4个元素创建一个切片 slice := arr[1:] //[1:len(arr)) slice := arr[:] //[0:len(arr))

using while_loop over the tensor for creating a mask in tensorflow

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问题 I want to create a mask with iterating over the tensor. I have this code: import tensorflow as tf out = tf.Variable(tf.zeros_like(alp, dtype=tf.int32)) rows_tf = tf.constant ( [[1, 2, 5], [1, 2, 5], [1, 2, 5], [1, 4, 6], [1, 4, 6], [2, 3, 6], [2, 3, 6], [2, 4, 7]]) columns_tf = tf.constant( [[1], [2], [3], [2], [3], [2], [3], [2]]) I want to iterate through rows_tf and accordingly columns_tf to create a mask over the out . for example, it will mask the index at [1,1] [2,1] and [5,1] in the

Appending to a slice with enough capacity using value receiver

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问题 can someone help me understand what happens here? package main import ( "fmt" ) func appendString(slice []string, newString string) { slice = append(slice, newString) } func main() { slice := make([]string, 0, 1) appendString(slice, "a") fmt.Println(slice) } I know about the slice header and the need to use a pointer receiver. But here, as the underlying array has enough capacity I would expect append to work anyways (just adding the new value to the underlying array and the original [copied]

group_by to select first two rows, then spread()

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问题 I'm trying to reformat this so I can generate a dataframe of all instances of On Hold Begins and the next event immediately after it. On Hold Begins is the start an event, and I'd like to capture its Timestamp and Deviation as well as the Timestamp and Deviation for the next event immediately after it (i.e. Below Thresold , Stage Enabled ). If possible, I only want to include slices that have On Hold Begins as the first event (so the ideal solution would not include rows 1 &2 above), do not

How to slice numbered lists into sublists

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问题 I have opened a file and used readlines() and split() with regex '\t' to remove TABs and it has resulted into the following lists: ["1", "cats", "--,"] ["2", "chase", "--,"] ["3", "dogs", "--,"] ["1", "the", "--,"] ["2", "car", "--,"] ["3", "is", "--,"] ["4", "gray", "--,"] Now I want to extract and slice this into sublists like "cats chase dogs" and "the car is gray" by looping the integers on index [0] as sentence boundaries. For instance 1 - 3 to sublist "cats chase dogs" and then continue

How to update a slice set, in an elegant way?

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问题 First, I want the top 250 users, and update their top = 1 users = MyTable.objects.order_by('-month_length')[0: 250] for u in users: u.top = 1 u.save() But, actually, I hope there is an elegent way, like this: MyTable.objects.all().update(top=1) And more, from this question: Django: Cannot update a query once a slice has been taken Does that mean CAN NOT WRITE UPDATE ... WHERE ... LIMIT 5 ? 回答1: Until the queryset has been evaluated once (at which point it will cache itself), slicing result in

Go - modify dereferenced struct pointer changes most struct values, but not slices

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问题 I'm trying to create a shallow copy of a struct Board (a chessboard). Before saving a move to the board, I need to check if that move puts the mover in check. To do so, within the Move method (method of a pointer), I dereference the pointer, update and check this possible board for Check. When I change the value of a single value of the Board type (such as possible.headers = "Possible Varient" ) the original b Board is not changed. But here when I call a method updateBoard() it updates both

Complexity of palindrome test

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问题 def is_palindrome(s): if len(s) <= 1: return True return s[0] == s[-1] and is_palindrome(s[1:-1]) My first thought was that the complexity is O(n) because each recursive call removes 2 characters. But then I thought of the slice's complexity. According to https://wiki.python.org/moin/TimeComplexity, the complexity of getting a slice is O(k), where k = number of elements in the slice. In is_palindrome , k = n - 2, then k = n - 4, then n - 6, etc. so I thought the complexity would be O(n^2)

PHP : Array Slice issue

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问题 I'm having a small issue in php and i know the solution is straightforward but i can't seem to get around to it. basically i have an array and i need small slices of it until the end. <?php $main = array(1,2,3,4,5,6,7,8,9,10,11,12,13,14,15); $start = 5; $sliced = array_slice($main, $start); $offset=3; $startx = $start; foreach($sliced as $s) { $start_pt = $startx-$offset; $end_pt = ($startx) - count($main); $sli = array_slice($main,$start_pt,$end_pt+1); print_r($sli); echo "<br>##############