Tutorial by Examples: f

Example for reading file data_file.csv such as: File: index,header1,header2,header3 1,str_data,12,1.4 3,str_data,22,42.33 4,str_data,2,3.44 2,str_data,43,43.34 7, str_data, 25, 23.32 Code: pd.read_csv('data_file.csv') Output: index header1 header2 header3 0 1 str_dat...

Models are typically defined in the models.py file under your application subdirectory. The Model class of django.db.models module is a good starting class to extend your models from. For example: from django.db import models class Book(models.Model): title = models.CharField(max_length=100...

Assuming python and python3 are both installed, it is possible to create a virtual environment for Python 3 even if python3 is not the default Python: virtualenv -p python3 foo or virtualenv --python=python3 foo or python3 -m venv foo or pyvenv foo Actually you can create virtual ...

The method nextInt(int bound) of Random accepts an upper exclusive boundary, i.e. a number that the returned random value must be less than. However, only the nextInt method accepts a bound; nextLong, nextDouble etc. do not. Random random = new Random(); random.nextInt(1000); // 0 - 999 int num...

NSArray *array = [NSArray arrayWithObjects:@"Nick", @"Ben", @"Adam", @"Melissa", nil]; NSPredicate *aPredicate = [NSPredicate predicateWithFormat:@"SELF beginswith[c] 'a'"]; NSArray *beginWithA = [array filteredArrayUsingPredicate:bPredicate]; ...

Simple record {-# LANGUAGE TemplateHaskell #-} import Control.Lens data Point = Point { _x :: Float, _y :: Float } makeLenses ''Point Lenses x and y are created. let p = Point 5.0 6.0 p ^. x -- returns 5.0 set x 10 p -- returns Point { _x = 10.0, _y = 6.0 } p & x +~ ...

By default error message appears below textbox in <div class="help-block"></div> on keyUp or after pressing submit button if any validation constraints aren't met. Sometimes we want a message on submit only i.e. no validation at onKeyup event. Let's check yii2/widgets/ActiveF...

A Kotlin interface contains declarations of abstract methods, and default method implementations although they cannot store state. interface MyInterface { fun bar() } This interface can now be implemented by a class as follows: class Child : MyInterface { override fun bar() { ...

An interface in Kotlin can have default implementations for functions: interface MyInterface { fun withImplementation() { print("withImplementation() was called") } } Classes implementing such interfaces will be able to use those functions without reimplementing cl...

Different flavors of application builds can contain different resources. To create a flavor-specific resource make a directory with the lower-case name of your flavor in the src directory and add your resources in the same way you would normally. For example, if you had a flavour Development and w...

You don't have to check the IDisposable object for null. using will not throw an exception and Dispose() will not be called: DisposableObject TryOpenFile() { return null; } // disposable is null here, but this does not throw an exception using (var disposable = TryOpenFile()) { //...

Java 8 provides classes called IntSummaryStatistics, DoubleSummaryStatistics and LongSummaryStatistics which give a state object for collecting statistics such as count, min, max, sum, and average. Java SE 8 List<Integer> naturalNumbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10); IntSu...

MATLAB comes with many built-in scripts and functions which range from simple multiplication to image recognition toolboxes. In order to get information about a function you want to use type: help functionname in the command line. Lets take the help function as an example. Information on how to use...

What is recursion: In general, recursion is when a function invokes itself, either directly or indirectly. For example: // This method calls itself "infinitely" public void useless() { useless(); // method calls itself (directly) } Conditions for applying recursion to a probl...

Content has been moved back to the good 'ol JSF wiki page

In this example, we will look at a method for returning the last non-empty row in a column for a data set. This method will work regardless of empty regions within the data set. However caution should be used if merged cells are involved, as the End method will be "stopped" against a mer...

Dart has If Else: if (year >= 2001) { print('21st century'); } else if (year >= 1901) { print('20th century'); } else { print('We Must Go Back!'); } Dart also has a ternary if operator: var foo = true; print(foo ? 'Foo' : 'Bar'); // Displays "Foo".

Two types of for loops are allowed: for (int month = 1; month <= 12; month++) { print(month); } and: for (var object in flybyObjects) { print(object); } The for-in loop is convenient when simply iterating over an Iterable collection. There is also a forEach method that you can cal...

enum MyEnum { One, Two, Three } foreach(MyEnum e in Enum.GetValues(typeof(MyEnum))) Console.WriteLine(e); This will print: One Two Three

The FlagsAttribute can be applied to an enum changing the behaviour of the ToString() to match the nature of the enum: [Flags] enum MyEnum { //None = 0, can be used but not combined in bitwise operations FlagA = 1, FlagB = 2, FlagC = 4, FlagD = 8 //you must use pow...