Tutorial by Examples: r

.after(delay, callback=None) is a method defined for all tkinter widgets. This method simply calls the function callback after the given delay in ms. If no function is given, it acts similar to time.sleep (but in milliseconds instead of seconds) Here is an example of how to create a simple timer us...

If you want to append a series of values [1,2] to the column of dataframe df, you will get NaNs: import pandas as pd series=pd.Series([1,2]) df=pd.DataFrame(index=[3,4]) df['col']=series df col 3 NaN 4 NaN because setting a new column automatically aligns the data by the inde...

The latest JVMs supports Garbage First GC ( G1 GC) and consists of set of regions which accumulate to make young and old generation. The JVM will have approximately 2048 reagions and set heap region size accordingly from 1 MB to 32 MB and power of 2 bounds. This is important parameter which decide ...

COMPUTE answer = 3*var-1 That is a reference to the variable var-1, and not var - 1. COMPUTE answer = 3 * var - 1 Recommended, opinion.

Scenario: You need to select an implementation of address validation when a sales order is submitted, and the validator is determined by the country to which the order is shipping. The factory needs to inspect some value passed as an argument to select the correct implementation. First, write an in...

Scenario: You need to resolve a dependency when a method is called, not in the constructor. Solution: Inject an abstract factory into the constructor. When the method is called, it requests the dependency from the abstract factory, which in turn resolves it from the container. (Your class depends o...

const Promise = require('bluebird'), fs = require('fs') Promise.promisifyAll(fs) // now you can use promise based methods on 'fs' with the Async suffix fs.readFileAsync('file.txt').then(contents => { console.log(contents) }).catch(err => { console.error('error reading', er...

Example of map: Promise.resolve([ 1, 2, 3 ]).map(el => { return Promise.resolve(el * el) // return some async operation in real world }) Example of filter: Promise.resolve([ 1, 2, 3 ]).filter(el => { return Promise.resolve(el % 2 === 0) // return some async operation in real world...

const promiseReturningFunction = Promise.coroutine(function* (file) { const data = yield fs.readFileAsync(file) // this returns a Promise and resolves to the file contents return data.toString().toUpperCase() }) promiseReturningFunction('file.txt').then(console.log)

function somethingThatReturnsADisposableResource() { return getSomeResourceAsync(...).disposer(resource => { resource.dispose() }) } Promise.using(somethingThatReturnsADisposableResource(), resource => { // use the resource here, the disposer will automatically close it when ...

Promise.resolve([1, 2, 3]) .mapSeries(el => Promise.resolve(el * el)) // in real world, use Promise returning async function .then(console.log)

const Koa = require('koa') const app = new Koa() app.use(async ctx => { ctx.body = 'Hello World' }) app.listen(8080)

app.use(async (ctx, next) => { try { await next() // attempt to invoke the next middleware downstream } catch (err) { handleError(err, ctx) // define your own error handling function } })

describe('Suite Name', function() { describe('#method()', function() { it('should run without an error', function() { expect([ 1, 2, 3 ].length).to.be.equal(3) }) }) })

var expect = require("chai").expect; describe('Suite Name', function() { describe('#method()', function() { it('should run without an error', function(done) { testSomething(err => { expect(err).to.not.be.equal(null) done() }) }) }) }) ...

describe('Suite Name', function() { describe('#method()', function() { it('should run without an error', function() { return doSomething().then(result => { expect(result).to.be.equal('hello world') }) }) }) })

Unlike var, const/let are bound to lexical scope rather than function scope. { var x = 1 // will escape the scope let y = 2 // bound to lexical scope const z = 3 // bound to lexical scope, constant } console.log(x) // 1 console.log(y) // ReferenceError: y is not defined console.log(z...

Arrow functions automatically bind to the 'this' lexical scope of the surrounding code. performSomething(result => { this.someVariable = result }) vs performSomething(function(result) { this.someVariable = result }.bind(this))

Before starting work with scrapy you have to start a project where you want to store your code. Enter the directory and run this code scrapy startproject helloProject The third part of this code is project name. This code will create a "helloProject" directory with the following conten...

You can qualify a whole folder folder for a specific device type, its files will override the ones outside it on that device: / DeviceFamily-Mobile PageOfEden.xaml MainPage.xaml MainPage.xaml MainPage.xaml.cs PageOfEden.xaml PageOfEden.xaml.cs Files inside the qualifying folder won...