Tutorial by Examples: b

Grouping numbers

For the following DataFrame: import numpy as np import pandas as pd np.random.seed(0) df = pd.DataFrame({'Age': np.random.randint(20, 70, 100), 'Sex': np.random.choice(['Male', 'Female'], 100), 'number_of_foo': np.random.randint(1, 20, 100)}) df.head() ...

pandas • Grouping Data

Accessing members of struct

In Swift, structures use a simple “dot syntax” to access their members. For example: struct DeliveryRange { var range: Double let center: Location } let storeLocation = Location(latitude: 44.9871, longitude: -93.2758) var pizzaRange = DeliveryRange(range: 200...

Swift Language • Structs

Enabling EdgeCache

In order to enable EdgeCache, set the following HTTP response headers (Do not deviate from this exact format): Cache-Control header to public, max-age=X where: X = the number of seconds that you want the response to be cached for X > 60 seconds X < 365*24*60*60 Set the Pragma he...

google-app-engine • EdgeCache

Instantiating sun.misc.Unsafe via bootclasspath

public class UnsafeLoader { public static Unsafe loadUnsafe() { return Unsafe.getUnsafe(); } } While this example will compile, it is likely to fail at runtime unless the Unsafe class was loaded with the primary classloader. To ensure that happens the JVM should be loaded with...

Java Language • sun.misc.Unsafe

Check for existence before dropping

MySQL3.19 DROP TABLE IF EXISTS MyTable; PostgreSQL8.x DROP TABLE IF EXISTS MyTable; SQL Server2005 If Exists(Select * From Information_Schema.Tables Where Table_Schema = 'dbo' And Table_Name = 'MyTable') Drop Table dbo.MyTable SQLite3.0 DROP TABLE IF EXI...

SQL • DROP Table

Multidex by using MultiDexApplication directly

Use this option if you don't need an Application subclass. This is the simplest option, but this way you can't provide your own Application subclass. If an Application subclass is needed, you will have to switch to one of the other options to do so. For this option, simply specify the fully-quali...

Android • Multidex and the Dex Method Limit

Multidex by extending Application

Use this option if your project requires an Application subclass. Specify this Application subclass using the android:name property in the manifest file inside the application tag. In the Application subclass, add the attachBaseContext() method override, and in that method call MultiDex.install():...

Android • Multidex and the Dex Method Limit

Block with

and



            
            
If the formatting (white space, new lines, indentation) of the code matters, use the pre element in combination with the code element:
&lt;pre&gt;
    &lt;code&gt;
    x = 42
    if x == 42:
        print &quot;x is …          … 42&quot;
    &lt;/code&gt;
&lt;/pre&gt;

You still have to esc...            

            
            
                
                    
                        HTML
                        •
                        Marking up computer code





    

        

            
            
                
                    Databinding in Fragment
                
            

            
            
Data Model
public class Item {
    private String name;

    public String getName() {
        return name;
    }

    public void setName(String name){
        this.name = name;
    }

}

Layout XML
&lt;?xml version=&quot;1.0&quot; encoding=&quot;utf-8&quot;?&gt;
&lt;layout xmlns:an...            

            
            
                
                    
                        Android
                        •
                        Data Binding Library
                        
                    
                    
                
            
        
    




    

        

            
            
                
                    Show Size of All Tables in Current Database 
                
            

            
            
SELECT
    s.name + '.' + t.NAME AS TableName,
    SUM(a.used_pages)*8 AS 'TableSizeKB'  --a page in SQL Server is 8kb
FROM sys.tables t
    JOIN sys.schemas s on t.schema_id = s.schema_id
    LEFT JOIN sys.indexes i ON t.OBJECT_ID = i.object_id
    LEFT JOIN sys.partitions p ON i.object_id = ...            

            
            
                
                    
                        Microsoft SQL Server
                        •
                        Retrieve information about the database
                        
                    
                    
                
            
        
    




    

        

            
            
                
                    Caller info attributes
                
            

            
            
Caller info attributes can be used to pass down information about the invoker to the invoked method. The declaration looks like this:
using System.Runtime.CompilerServices;

public void LogException(Exception ex,
                         [CallerMemberName]string callerMemberName = &quot;&quot;,
...            

            
            
                
                    
                        C# Language
                        •
                        Attributes
                        
                    
                    
                
            
        
    




    

        

            
            
                
                    Converting to boolean
                
            

            
            
Boolean(...) will convert any data type into either true or false.
Boolean(&quot;true&quot;) === true
Boolean(&quot;false&quot;) === true
Boolean(-1) === true
Boolean(1) === true
Boolean(0) === false
Boolean(&quot;&quot;) === false
Boolean(&quot;1&quot;) === true
Boolean(&quot;0&quot;) === t...            

            
            
                
                    
                        JavaScript
                        •
                        Variable coercion/conversion
                        
                    
                    
                
            
        
    




    

        

            
            
                
                    Use Custom Theme Globally
                
            

            
            
In themes.xml:
&lt;style name=&quot;AppTheme&quot; parent=&quot;Theme.AppCompat&quot;&gt;
    &lt;!-- Theme attributes here --&gt;
&lt;/style&gt;

In AndroidManifest.xml:
&lt;application
    android:icon=&quot;@mipmap/ic_launcher&quot;
    android:label=&quot;@string/app_name&quot;
    andr...            

            
            
                
                    
                        Android
                        •
                        Theme, Style, Attribute
                        
                    
                    
                
            
        
    




    

        

            
            
                
                    Basic decoding / unmarshalling of nested elements with data
                
            

            
            
XML elements often nest, have data in attributes and/or as character data. The way to capture this data is by using ,attr and ,chardata respectively for those cases.
var doc = `
&lt;parent&gt;
  &lt;child1 attr1=&quot;attribute one&quot;/&gt;
  &lt;child2&gt;and some cdata&lt;/child2&gt;
&lt;/p...            

            
            
                
                    
                        Go
                        •
                        XML
                        
                    
                    
                
            
        
    




    

        

            
            
                
                    Making a custom object Parcelable.
                
            

            
            
/**
 * Created by Alex Sullivan on 7/21/16.
 */
public class Foo implements Parcelable
{
    private final int myFirstVariable;
    private final String mySecondVariable;
    private final long myThirdVariable;

    public Foo(int myFirstVariable, String mySecondVariable, long myThirdVariab...            

            
            
                
                    
                        Android
                        •
                        Parcelable
                        
                    
                    
                
            
        
    




    

        

            
            
                
                    Basic creation and playing
                
            

            
            
MediaPlayer class can be used to control playback of audio/video files and streams.
Creation of MediaPlayer object can be of three types:


Media from local resource
MediaPlayer mediaPlayer = MediaPlayer.create(context, R.raw.resource);
mediaPlayer.start(); // no need to call prepare(); create...            

            
            
                
                    
                        Android
                        •
                        MediaPlayer
                        
                    
                    
                
            
        
    




    

        

            
            
                
                    Basic reflect.Value Usage
                
            

            
            

import "reflect"

value := reflect.ValueOf(4)

// Interface returns an interface{}-typed value, which can be type-asserted
value.Interface().(int) // 4

// Type gets the reflect.Type, which contains runtime type information about
// this value
value.Type().Name() // int

value.SetInt(5)...            

            
            
                
                    
                        Go
                        •
                        Reflection
                        
                    
                    
                
            
        
    




    

        

            
            
                
                    Built-In Types Table
                
            

            
            
The following table shows the keywords for built-in C# types, which are aliases of predefined types in the System namespaces.
C# Type.NET Framework TypeboolSystem.BooleanbyteSystem.BytesbyteSystem.SBytecharSystem.ChardecimalSystem.DecimaldoubleSystem.DoublefloatSystem.SingleintSystem.Int32uintSyste...            

            
            
                
                    
                        C# Language
                        •
                        Aliases of built-in types
                        
                    
                    
                
            
        
    




    

        

            
            
                
                    Strings and immutability
                
            

            
            
Immutable types are types that when changed create a new version of the object in memory, rather than changing the existing object in memory. The simplest example of this is the built-in string type.
Taking the following code, that appends &quot; world&quot; onto the word &quot;Hello&quot;
string ...            

            
            
                
                    
                        C# Language
                        •
                        Immutability
                        
                    
                    
                
            
        
    




    

        

            
            
                
                    The Serializable interface
                
            

            
            
Introduction

Classes that implement this interface no longer support __sleep() and __wakeup(). The method serialize is called whenever an instance needs to be serialized. This does not invoke __destruct() or has any other side effect unless programmed inside the method. When the data is unseriali...            

            
            
                
                    
                        PHP
                        •
                        Object Serialization