Tutorial by Examples: ar

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...

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...

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 } })

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))

Let's assume we have an Image element using a square image named Picture.png. We can use different files for each dimension set for the element. Picture.TargetSize-16.png Picture.TargetSize-32.png Picture.TargetSize-128.png Now if we set the Height or Width of our Image to 16px, it will use P...

Multidimensional arrays follow the same rules as single-dimensional arrays when passing them to a function. However the combination of decay-to-pointer, operator precedence, and the two different ways to declare a multidimensional array (array of arrays vs array of pointers) may make the declaratio...

First of all, the problem of handling spaces in arguments is NOT actually a Java problem. Rather it is a problem that needs to be handled by the command shell that you are using when you run a Java program. As an example, let us suppose that we have the following simple program that prints the siz...

Write some tests Install dispatch:mocha-phantomjs: meteor add dispatch:mocha-phantomjs Add a test-command to your package.json. { "name": "awesome meteor package", "scripts": { "test": "meteor test --driver-package dispatch:mocha-...

Sinse structs are value types all the data is copied on assignment, and any modification to the new copy does not change the data for the original copy. The code snippet below shows that p1 is copied to p2 and changes made on p1 does not affect p2 instance. var p1 = new Point { x = 1, y =...

To create new archive open zipfile with write mode. import zipfile new_arch=zipfile.ZipFile("filename.zip",mode="w") To add files to this archive use write() method. new_arch.write('filename.txt','filename_in_archive.txt') #first parameter is filename and second parameter i...

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Although storing multiple values in a single column violates normalization rules, sometimes one has to deal with badly designed legacy tables. A recursive query can help convert comma-separated values into distinct rows. Create a sample badly designed table and insert some data: create table proje...

On Unix-like operating systems, it is possible to use the pkg-config program to find and configure packages that provides a <package>.pc file. In order to use pkg-config, it is necessary to call include(FindPkgConfig) in a CMakeLists.txt. Then, there are 2 possible functions: pkg_search_mo...

Using the /p switch with the SET command you can define variables from an Input. This input can be a user Input (keyboard) : echo Enter your name : set /p name= echo Your name is %name% Which can be simplified like this : set /p name=Enter your name : echo Your name is %name% Or you can...

libraryDependency is the SettingKey that handles 'managed' library dependencies, which are dependencies that are automatically downloaded, matching the supplied versions. To add a single dependency: libraryDependencies += "com.typesafe.slick" %% "slick" % "3.2.0-M1" ...

A repository is a place that SBT looks for libraryDependencies. If the build complains about not finding a dependency, it can be lacking the correct repository. Within SBT, the repositories are listed in the resolvers SettingKey: resolvers += "Flyway" at "https://flywaydb.org/repo&qu...