conditional | 易学教程

Is there such thing as not less than? [closed]

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问题 Closed. This question does not meet Stack Overflow guidelines. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 3 years ago . In my code, I'm trying to make a not less than operator. I can't do a !< b ... what can I do? Is there any package / method I can use? 回答1: The opposite of a<b is a>=b , not a>b . EDIT: The syntax you were looking for is !(a<b) 回答2: Oh, I am so stupid! I could just do a >= b ! 来源：

Is there such thing as not less than? [closed]

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Conditional operations on numpy arrays

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问题 I'm new to NumPy, and I've encountered a problem with running some conditional statements on numpy arrays. Let's say I have 3 numpy arrays that look like this: a: [[0, 4, 4, 2], [1, 3, 0, 2], [3, 2, 4, 4]] b: [[6, 9, 8, 6], [7, 7, 9, 6], [8, 6, 5, 7]] and, c: [[0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0]] I have a conditional statement for a and b in which I would like to use the value of b (if the conditions of a and b are met) to calculate the value of c: c[(a > 3) & (b > 8)]+=b*2 I get an

How do I conditionally check if an enum is one variant or another?

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问题 I have an enum with two variants: enum DatabaseType { Memory, RocksDB, } What do I need in order to make a conditional if inside a function that checks if an argument is DatabaseType::Memory or DatabaseType::RocksDB ? fn initialize(datastore: DatabaseType) -> Result<V, E> { if /* Memory */ { //.......... } else if /* RocksDB */ { //.......... } } 回答1: First, go back and re-read the free, official Rust book : The Rust Programming Language, specifically the chapter on enums. match fn initialize

Pandas: How to sum columns based on conditional of other column values?

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问题 I have the following pandas DataFrame. import pandas as pd df = pd.read_csv('filename.csv') print(df) dog A B C 0 dog1 0.787575 0.159330 0.053095 1 dog10 0.770698 0.169487 0.059815 2 dog11 0.792689 0.152043 0.055268 3 dog12 0.785066 0.160361 0.054573 4 dog13 0.795455 0.150464 0.054081 5 dog14 0.794873 0.150700 0.054426 .. .... 8 dog19 0.811585 0.140207 0.048208 9 dog2 0.797202 0.152033 0.050765 10 dog20 0.801607 0.145137 0.053256 11 dog21 0.792689 0.152043 0.055268 .... I create a new column

关于C# 中的Attribute 特性

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摘要：纠结地说，这应该算是一篇关于Attribute 的笔记，其中的一些思路和代码借鉴了他人的文笔（见本文底部链接）。但是，由于此文对Attribute 的讲解实在是叫好（自夸一下 ^_^），所以公之于众，希望能对大家有所帮助。　　 Attribute与Property 的翻译区别　　Attribute 一般译作“特性”，Property 仍然译为“属性”。　　 Attribute 是什么　　Attribute 是一种可由用户自由定义的修饰符（Modifier），可以用来修饰各种需要被修饰的目标。　　简单的说，Attribute就是一种“附着物” —— 就像牡蛎吸附在船底或礁石上一样。　　这些附着物的作用是为它们的附着体追加上一些额外的信息（这些信息就保存在附着物的体内）—— 比如“这个类是我写的”或者“这个函数以前出过问题”等等。　　 Attribute 的作用　　特性Attribute 的作用是添加元数据。　　元数据可以被工具支持，比如：编译器用元数据来辅助编译，调试器用元数据来调试程序。　　 Attribute 与注释的区别注释是对程序源代码的一种说明，主要目的是给人看的，在程序被编译的时候会被编译器所丢弃，因此，它丝毫不会影响到程序的执行。而Attribute是程序代码的一部分，不但不会被编译器丢弃，而且还会被编译器编译进程序集（Assembly

MVCC在分布式系统中的应用

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问题最近项目中遇到了一个分布式系统的并发控制问题。该问题可以抽象为：某分布式系统由一个数据中心D和若干业务处理中心L1，L2 ... Ln组成；D本质上是一个key-value存储，它对外提供基于HTTP协议的CRUD操作接口。L的业务逻辑可以抽象为下面3个步骤： read: 根据keySet {k1, ... kn}从D获取keyValueSet {k1:v1, ... kn:vn} do: 根据keyValueSet进行业务处理，得到需要更新的数据集keyValueSet' {k1':v1', ... km':vm'} ( 注：读取的keySet和更新的keySet'可能不同) update: 把keyValueSet'更新到D （注：D保证在一次调用更新多个key的原子性）在没有事务支持的情况下，多个L进行并发处理可能会导致数据一致性问题。比如，考虑L1和L2的如下执行顺序： L1从D读取key:123对应的值100 L2从D读取key:123对应的100 L1对值增加1，将key:123更新为100 + 1 L2对值增加2，将key:123更新为100 + 2 如果L1和L2串行执行，key:123对应的值将为103，但上面并发执行中L1的执行效果完全被L2所覆盖，实际key:123所对应的值变成了102。解决方案1：锁机制为了让L的处理可串行化

How do you conditionally show fields in “Show” component in react-admin?

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问题 Some fields I want to only show if they have a value. I would expect to do this like so: <Show {...props} > <SimpleShowLayout> { props.record.id ? <TextField source="id" />: null } </SimpleShowLayout> </Show> But that doesn't work. I can make it somewhat work by making each field a higher order component, but I wanted to do something cleaner. Here's the HOC method I have: const exists = WrappedComponent => props => props.record[props.source] ? <WrappedComponent {...props} />: null; const

How do you conditionally show fields in “Show” component in react-admin?

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关于 @Conditional 注解

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关于 @Conditional 注解背景在我们项目中，有时候需要实现这样的需求。我有个接口I，接口的实现类有A、B，我需要的效果是通过不同的配置，实例化具体某个实现类，即可以选择实例化A或B 在spring中，有个注解 @Conditional 可以实现这个要求。我们先来最简单的例子1 1、例子1 接口1个 public interface PrinterService { String print ( String content ) ; } 具体实现2个 @Service @Conditional ( PrinterServiceConditional . InkCondition . class ) public class InkPrinterServiceImpl implements PrinterService { @Override public String print ( String content ) { return "喷墨打印机打印：" + content ; } } @Service @Conditional ( PrinterServiceConditional . LaserCondition . class ) public class LaserPrinterServiceImpl implements PrinterService {

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