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How to obtain the number of CPUs/cores in Linux from the command line?
...
The most portable solution I have found is the getconf command:
getconf _NPROCESSORS_ONLN
This works on both Linux and Mac OS X. Another benefit of this over some of the other approaches is that getconf has been around for a long time. Some of the older Linux machines I have to do development o...
Any reason not to use '+' to concatenate two strings?
...ucture, especially if it is growing. With list you can use list.extend(list_of_items) and list.append(item) which are much faster when concatenating stuff dynamically.
– Antti Haapala
Sep 11 '12 at 9:56
...
How to convert CFStringRef to NSString?
...e using ARC, the new casting syntax is as follows:
NSString *aNSString = (__bridge NSString *)aCFString;
works as well. The key thing to note is that CoreFoundation will often return objects with +1 reference counts, meaning that they need to be released (all CF[Type]Create format functions do th...
Does use of final keyword in Java improve the performance?
...(at compile time).
public class FinalTest {
public static final int N_ITERATIONS = 1000000;
public static String testFinal() {
final String a = "a";
final String b = "b";
return a + b;
}
public static String testNonFinal() {
String a = "a";
...
MQTT客户端内置版使用指导 · App Inventor 2 中文网
...入口。
案例一：连接并订阅
when 按钮_连接.Click() {
MqttClient1.Connect(true)
}
when MqttClient1.ConnectionStateChanged(新状态, 状态文本) {
标签1.Text = 状态文本
if MqttClient1.IsConnected {
MqttClient1.Subscribe("demo/status", 0)
}
}
...
How to calculate moving average using NumPy?
... an off-by-one wrong indexing spotted by Bean in the code. EDIT
def moving_average(a, n=3) :
ret = np.cumsum(a, dtype=float)
ret[n:] = ret[n:] - ret[:-n]
return ret[n - 1:] / n
>>> a = np.arange(20)
>>> moving_average(a)
array([ 1., 2., 3., 4., 5., 6., 7....
App Inventor 2 数据可视化教程 - 折线图/曲线图/实时数据绘图 · App Inventor 2 中文网
...线图）
积木块：
// 全局变量
global x计数 = 0
when 按钮_开始.Click() {
计时器1.TimerEnabled = true
二维图表数据1.Clear()
}
when 计时器1.Timer() {
global x计数 = x计数 + 1
global 随机值 = randomInteger(1, 100)
二维图表数据1.AddEntry(x计数, 随...
How to get Scala List from Java List?
...now built into the language using:
import scala.collection.JavaConversions._
...
lst.toList.foreach{ node => .... }
works. asScala did not work
In 2.12.x use import scala.collection.JavaConverters._
In 2.13.x use import scala.jdk.CollectionConverters._
...
PDO closing connection
...>connection = new PDO();
$this->connection->query('KILL CONNECTION_ID()');
$this->connection = null;
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How to implement the --verbose or -v option into a script?
...unction (or if you're willing to use print as a function in 2.x using from __future__ import print_function) it's even simpler:
verboseprint = print if verbose else lambda *a, **k: None
This way, the function is defined as a do-nothing if verbose mode is off (using a lambda), instead of constantl...