Tutorial by Examples: re

Start a named process on one IP address: $ iex --name [email protected] --cookie chocolate iex([email protected])> Node.ping :"[email protected]" :pong iex([email protected])> Node.list [:"[email protected]"] Start another named process on a different IP address: $ iex ...

Example uses basic HTTP syntax. Any <#> in the example should be removed when copying it. You can use the _cat APIs to get a human readable, tabular output for various reasons. GET /_cat/health?v <1> The ?v is optional, but it implies that you want "verbose" output. _...

All files are in folder files. First create list of DataFrames and then concat them: import pandas as pd import glob #a.csv #a,b #1,2 #5,8 #b.csv #a,b #9,6 #6,4 #c.csv #a,b #4,3 #7,0 files = glob.glob('files/*.csv') dfs = [pd.read_csv(fp) for fp in files] #duplicated ind...

The ** operator works similarly to the * operator but it applies to keyword parameters. def options(required_key:, optional_key: nil, **other_options) other_options end options(required_key: 'Done!', foo: 'Foo!', bar: 'Bar!') #> { :foo => "Foo!", :bar => "Bar!" ...

.Net 4.0 type Lazy guarantees thread-safe object initialization, so this type could be used to make Singletons. public class LazySingleton { private static readonly Lazy<LazySingleton> _instance = new Lazy<LazySingleton>(() => new LazySingleton()); public stati...

Finding patterns in data often proceeds in a chain of data-processing steps, e.g., feature selection, normalization, and classification. In sklearn, a pipeline of stages is used for this. For example, the following code shows a pipeline consisting of two stages. The first scales the features, and t...

Consider this simple class: class SmsUtil { public bool SendMessage(string from, string to, string message, int retryCount, object attachment) { // Some code } } Before C# 3.0 it was: var result = SmsUtil.SendMessage("Mehran", "Maryam", "Hello...

Responses can be written to a http.ResponseWriter using templates in Go. This proves as a handy tool if you wish to create dynamic pages. (To learn how Templates work in Go, please visit the Go Templates Documentation page.) Continuing with a simple example to utilise the html/template to respond ...

In order to install PostgreSQL on OSX, you need to know which versions are currently supported. Use this command to see what versions you have available. sudo port list | grep "^postgresql[[:digit:]]\{2\}[[:space:]]" You should get a list that looks something like the following: post...

CREATE CONTEXT my_ctx USING my_pkg; This creates a context that can only be set by routines in the database package my_pkg, e.g.: CREATE PACKAGE my_pkg AS PROCEDURE set_ctx; END my_pkg; CREATE PACKAGE BODY my_pkg AS PROCEDURE set_ctx IS BEGIN DBMS_SESSION.set_context('MY_CTX','...

The RewriteEngine module within Apache is used to dynamically rewrite URLs and paths depending on various expressions provided: <IfModule mod_rewrite.c> RewriteEngine On RewriteBase / RewriteRule ^index\.php$ - [L] RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d ...

When it comes to geographic data, R shows to be a powerful tool for data handling, analysis and visualisation. Often, spatial data is avaliable as an XY coordinate data set in tabular form. This example will show how to create a spatial data set from an XY data set. The packages rgdal and sp provi...

Concurrent collections are a generalization of thread-safe collections, that allow for a broader usage in a concurrent environment. While thread-safe collections have safe element addition or removal from multiple threads, they do not necessarily have safe iteration in the same context (one may not...

The difference between size and count is: size counts NaN values, count does not. df = pd.DataFrame( {"Name":["Alice", "Bob", "Mallory", "Mallory", "Bob" , "Mallory"], "City":["Seattle", &q...

x=anObject.aProperty.anotherProperty.getSomething().data; Here, any object before the dot can end up being null, and using methods that return complex objects only increases the complication to debug the null error. Worst case if the method is prone to extraneous failures, say retrieving data ove...

s=this.getChildByName("garbage"); if (s.parent==this) {...} getChildByName() is one of the many functions that can return null if an error occurred when processing its input. Therefore, if you are receiving an object from any function that can possibly return null, check for null first...

Rescue from record not found error instead of showing an exception or white page: class ApplicationController < ActionController::Base # ... your other stuff here rescue_from ActiveRecord::RecordNotFound do |exception| redirect_to root_path, 404, alert: 'Record not found' en...

This helper validates that the specified attributes are not empty. class Person < ApplicationRecord validates :name, presence: true end Person.create(name: "John").valid? # => true Person.create(name: nil).valid? # => false You can use the absence helper to validate th...

You can create parser error messages according to your script needs. This is through the argparse.ArgumentParser.error function. The below example shows the script printing a usage and an error message to stderr when --foo is given but not --bar. import argparse parser = argparse.ArgumentParser...

First: The path structure If you don't have it you need to create the middleware folder within your app following the structure: yourproject/yourapp/middleware The folder middleware should be placed in the same folder as settings.py, urls, templates... Important: Don't forget to create the ini...