slice | 易学教程

array_slice but for images php

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问题 i have written this code <?php $a = Meme::all(); $b = count($a); for($i=$b;$i<$b-3;$i--) { ?> <div class="col-sm-6"><img class="lazy" data-src="<?php echo $a[$i]->path; ?>" /> </div> <?php }?> i want to output the last 3 memes(images) but this for loop doesn't work. So i found something that is called array_slice and i wanted to use it but everyone was using print_r but in this case i don't need it. So any suggestions? 回答1: Store those 3 elements of array $a in a new array $b by using array

Go slice length is capacity -1, why?

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问题 Consider the go code below: fruits := [4]string{"apple", "orange", "mango"} tasty_fruits := fruits[1:3] fmt.Println(len(tasty_fruits)) fmt.Println(cap(tasty_fruits)) fmt.Println(tasty_fruits) Ouputs: 2 3 [orange mango] What I don't understand is why is the capacity of tasty_fruits 3, intuitively I would expect it to be 2 since that is the length of the slice? And if the capacity of tasty_fruits is 3 why does: tasty_fruits[2] = "nectarine" result in: panic: runtime error: index out of range

Slicing list inside a method (Python 3)

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问题 I have a method like the following: def slice_list(my_list, slice_point): my_list = my_list[:slice_point] print("Inside method: ", my_list) return I have a test for it like the following: if __name__ == "__main__": my_list = [1,2,3,4,5] slice_point = 3 slice_list(my_list, slice_point) print("Outside method: ", my_list) The output I get is not what I expected for, in the sense that the list is not ultimately edited >>>Inside method: [1, 2, 3] >>>Outside method: [1, 2, 3, 4, 5] But when I do an

using references to point to sliding window array in Perl

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问题 here is my problem: I have 2 arrays. One is character array and represents a sliding window. Characters gets shifted from the beginning and pushed at the end. I would like to use a second array to store references to array slices that 'follow' the characters as they move along. Example: my @char_array = ('h','e','l','l','o','w','o','r','l','d'); my $char_arr_ref=[@char_array[1..$#char_array]]; print @$char_arr_ref, "\n"; # slice contains 'elloworld'; shift(@char_array); push(@char_array), 'x'

using references to point to sliding window array in Perl

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Python:slice与indices

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slice: 　　eg: 　　　　>>>e=[0,1,2,3,4,5,6] 　　　　>>>s=slice(2,3) 　　　　>>>e[s] 　　　　[2] 　　　　slice的区间左闭右开[）　　　　>>>s 　　　　slice(2,3,None) 　　　　slice([strar,]stop[,step]),start缺少时就是0 indices: 　　eg: 　　　　>>>print(s.indices(100)) 　　　　(2,3,1) 　　　　>>>print(s.indices(3)) 　　　　(2,3,1) 　　　　>>>print(s.indices(2)) 　　　　(2,2,1) 　　　　>>>e[s] 　　　　[2] 　　　　这个indices相当于stop的位置,只要是大于之前的stop索引，按之前的来，否则就取小索引转载：https://www.cnblogs.com/baxianhua/p/8145324.html 来源： CSDN 作者：西奥之LSM 链接： https://blog.csdn.net/qq_33673213/article/details/103791097

The zero value of a slice is not nil

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问题 I was following the example https://tour.golang.org/moretypes/10 I modified the code expecting to get the same result. I did not. Is this a bug, or a documentation error? The tour states A nil slice has a length and capacity of 0. My y variable has a length and capacity of 0. package main import "fmt" func myPrint(z []int) { fmt.Println(z, len(z), cap(z)) if z == nil { fmt.Println("nil!") } } func main() { var z []int y := []int {} myPrint(z) myPrint(y) } Here is my output. [] 0 0 nil! [] 0 0

slice pandas timeseries on date +/- 2 business days

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问题 having following timeseries: In [65]: p Out[65]: Date 2008-06-02 125.20 2008-06-03 124.47 2008-06-04 124.40 2008-06-05 126.89 2008-06-06 122.84 2008-06-09 123.14 2008-06-10 122.53 2008-06-11 120.73 2008-06-12 121.19 Name: SPY how can I slice on a specfic date +/- 2 neighbouring (business) days, so ie if d = '2008-06-06': -2 2008-06-04 124.40 -1 2008-06-05 126.89 0 2008-06-06 122.84 1 2008-06-09 123.14 2 2008-06-10 122.53 回答1: You could use the index method get_loc, and then slice: d = pd.to

Why does assigning past the end of a list via a slice not raise an IndexError? [duplicate]

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问题 This question already has answers here : Why does substring slicing with index out of range work? (3 answers) Closed 3 years ago . I'm working on a sparse list implementation and recently implemented assignment via a slice. This led me to discover some behaviour in Python's built-in list implementation that I find suprising. Given an empty list and an assignment via a slice: >>> l = [] >>> l[100:] = ['foo'] I would have expected an IndexError from list here because the way this is implemented

MIT6.824 Lab1 MapReduce

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MapReduce分布式计算框架 MapReduce是谷歌开发的分布式计算框架。MapReduce需用户指定Map和Reduce两个函数具体操作内容。现实世界大多数计算操作都可以基于该操作完成。 Map&&Reduce操作 Map MapReduce按照记录读取文件，针对每条记录执行Map操作，将记录转化为KeyValues形式保存到中间文件中（根据Key的哈希值映射到指定文件中，文件如何分割根据partition函数） Reduce Reduce 读取中间文件，将相同Key的多个Values合并成到一个Value中。 MapReduce计算框架结构： MapReduce 首先将输入文件划分成M份放入到worker中，每个worker中都有一份代码的副本其中一份副本作为master，其他worker被master分配工作。设定M个map任务以及R个reduce任务。master选择空闲的worker分配map任务或者reduce任务分配map任务的worker，将输入文件的内容利用map函数将其解析为key-value，放入到内存中。与此同时，内存中key-value pair分为R个文件写入到磁盘中。将文件地址传给master。 reduce worker收到文件地址后，利用远程过程调用（RPC）读取所有中间文件，根据key值对文件排序（相同key的pair组成一起）