slice | 易学教程

Perl: slicing an array of hashes

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问题 The output of the code below is always empty. Not sure what I am doing wrong and would appreciate any help. How do I get to the values of a key in a specific hash in an array of hashes? use strict; use warnings; my %dot1 = ('a'=>1,'b'=>2); my %dot2 = ('a'=>3,'b'=>4); my %dot3 = ('a'=>5,'b'=>6); my %dot4 = ('a'=>7,'b'=>8); my @array = (%dot1,%dot2,%dot3,%dot4); my %x = $array[2]; my $y = $x->{'a'}; print "$y \n"; 回答1: If you want an array of hash references, you need to say so explicitly. my

Combining slicing and broadcasted indexing for multi-dimensional numpy arrays

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I have a ND numpy array (let say for instance 3x3x3) from wich I'd like to extract a sub-array, combining slices and index arrays. For instance: import numpy as np A = np.arange(3*3*3).reshape((3,3,3)) i0, i1, i2 = ([0,1], [0,1,2], [0,2]) ind1 = j0, j1, j2 = np.ix_(i0, i1, i2) ind2 = (j0, slice(None), j2) B1 = A[ind1] B2 = A[ind2] I would expect that B1 == B2, but actually, the shapes are different >>> B1.shape (2, 3, 2) >>> B2.shape (2, 1, 2, 3) >>> B1 array([[[ 0, 2], [ 3, 5], [ 6, 8]], [[ 9, 11], [12, 14], [15, 17]]]) >>> B2 array([[[[ 0, 3, 6], [ 2, 5, 8]]], [[[ 9, 12, 15], [11, 14, 17]]]]

pytorch笔记

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pytorch Tensor slice 以[2,3]矩阵为例,slice后可以得到任意shape的矩阵,并不是说一定会小于2行3列. import torch truths=torch.Tensor([[1,2,3],[4,5,6]]) #代表新生成一个[3,]的矩阵,行位置分别取原先矩阵的第1,第0,第1行. print(truths[[1,0,1],:]) print(truths[[1,0,1]]) #等同于truths[[1,0,1],:] #代表新生成一个[,4]的矩阵,列位置分别取原先矩阵的第2,第2,第2,第2列 print(truths[:,[2,2,2,2]]) 输出来源： https://www.cnblogs.com/sdu20112013/p/11731741.html

How to pass multiple values from template to template?

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问题 My City struct is like this: type City struct { ID int Name string Regions []Region } And Region struct is: type Region struct { ID int Name string Shops []Destination Masters []Master EducationCenters []Destination } In main I try to do this: tpl.ExecuteTemplate(resWriter,"cities.gohtml",CityWithSomeData) Is it possible to do something like this inside template? {{range .}} {{$city:=.Name}} {{range .Regions}} {{$region:=.Name}} {{template "data" .Shops $city $region}} {{end}} {{end}} 回答1:

Golang学习笔记--Array和Slice

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目录 Reference Array Slice slice的创建 Slice常用操作 reslice append函数 copy函数 range遍历 Reference https://blog.golang.org/go-slices-usage-and-internals Array 数组是值类型，赋值和传参会复制整个数组，而不是指针。数组⻓长度必须是常量，且是类型的组成部分。[2]int 和 [3]int 是不同类型。⽀支持 "=="、"!=" 操作符，因为内存总是被初始化过的。指针数组 [n]*T，数组指针 *[n]T。 Slice 因为array是值类型，赋值和传参行为使用array都会发生数据拷贝，如果操作对象是比较大的array，那么时间和空间上的开销都会成为问题。 7 func arrayAsParamTest() { 8 fmt.Println("=========SliceTest.sliceAsParamTest()==========") 9 arrayA := [2]int{1, 2} 10 var arrayB [2]int 11 arrayB = arrayA 12 fmt.Printf("Address: %p.\n", &arrayA) 13 fmt.Printf("Address: %p.\n", &arrayB) 14

Slice pandas multiindex dataframe using list of index values [duplicate]

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This question already has an answer here: Select rows in pandas MultiIndex DataFrame 1 answer I have a multi-index dataframe that looks like uid tid text abc x t1 bcd y t2 uid and tid are the indexes. I have a list of uid s, and want to get the rows corresponding to the uids in that list, but keeping the 2nd level index values (tid). I want to do it without running any explicit loop. Is that possible? Data: L = ['abc', 'bcd'] print (df) text uid tid abc x t1 abc1 x t1 bcd y t2 1. slicers idx = pd.IndexSlice df1 = df.loc[idx[L,:],:] 2. boolean indexing + mask with get_level_values + isin : df1

Golang精编100题-搞定golang面试

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分享一下我老师大神的人工智能教程！零基础，通俗易懂！ http://blog.csdn.net/jiangjunshow 也欢迎大家转载本篇文章。分享知识，造福人民，实现我们中华民族伟大复兴！ Golang 精编 100 题能力模型级别模型初级 primary 熟悉基本语法，能够看懂代码的意图；在他人指导下能够完成用户故事的开发，编写的代码符合 CleanCode 规范；中级 intermediate 能够独立完成用户故事的开发和测试；能够嗅出代码的坏味道，并知道如何重构达成目标；高级 senior 能够开发出高质量高性能的代码；能够熟练使用高级特性，开发编程框架或测试框架；选择题 1. 【初级】下面属于关键字的是（） A. func B. def C. struct D. class 参考答案： AC 2. 【初级】定义一个包内全局字符串变量，下面语法正确的是（） A. var str string B. str := "" C. str = "" D. var str = "" 参考答案： AD 3. 【初级】通过指针变量 p 访问其成员变量 name ，下面语法正确的是（） A. p.name B. (*p).name C. (&p).name D. p->name 参考答案： AB 4. 【初级】关于接口和类的说法，下面说法正确的是（） A.

Zeroc ICE 之zeroc Registry(Java)

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zeroc文档很少，都是我采用“穷举法“踩坑，一个一个摸索。 1.首先在windows中安装zeroc ice，在eclipse中安装Ice Builder插件 2.新建一个java项目（如上图），然后用Ice Builder插件构建生成generated文件夹。在项目下新建文件夹slice 3.在slice文件夹下新建service.ice和SMSService.ice(如上图) service.ice代码如下: [["java:package:com.hp.tel.ice"]] module book{ struct Message{ string name; int type; bool valid; double price; string content; }; interface OnlineBook{ Message bookTick(Message msg); }; } ; SMSService.ice代码如下: [["java:package:com.hp.tel.ice"]] module message{ interface SMSService{ void sendSMs(string msg); }; }; 然后，会在generated文件下生成代码。 4.OnlineBookI2.java 代码如下: package com.hp.impl;

Efficient way to check IP in slice of IP addresses in Golang

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I'm developing a network application in Golang. I have a slice of IP addresses. Each time a request comes I use net.LookupIP(host) to find out IP address of host which returns a slice of net.IP . What is the best approach to compare these? By the way in Python we have a set data structure which makes above question so easy to resolve but what about Go? icza With a "set" Building our set There is no builtin Set type in Go, but you can elegantly use a map[Type]bool as a set, e.g.: // Create a set with 2 values in it: [1, 2] m := map[int]bool{1: true, 2: true} // Test an element: fmt.Println(m[1]

Store information/reference about structure

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I am looking for a way to store information which struct a function should use. Each struct corresponds to certain database table. type Record struct { TableName string PrimaryKey string //XormStruct // how can I store User or Post here? XormStruct2 interface{} // see I have tried below XormStruct3 reflect.Type // see I have tried below } var posts []Post var ListOfTables [...]Record { {"User", "id", User}, //{"Post", "post_id", Post}, {"Post", "post_id", posts, reflect.TypeOf([]Post{})}, } // User is xorm struct type User struct { Id int64 Name string } // Post is xorm struct type Post struct

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