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Python will implicitly convert any object to a Boolean value for testing, so use it wherever possible. # Good examples, using implicit truth testing if attr: # do something if not attr: # do something # Bad examples, using specific types if attr == 1: # do something if att...

The query attribute on queryset gives you SQL equivalent syntax for your query. >>> queryset = MyModel.objects.all() >>> print(queryset.query) SELECT "myapp_mymodel"."id", ... FROM "myapp_mymodel" Warning: This output should only be used for d...

To get First object: MyModel.objects.first() To get last objects: MyModel.objects.last() Using Filter First object: MyModel.objects.filter(name='simple').first() Using Filter Last object: MyModel.objects.filter(name='simple').last()

Web applications often require static files like CSS or JavaScript files. To use static files in a Flask application, create a folder called static in your package or next to your module and it will be available at /static on the application. An example project structure for using templates is as f...

In an enum it is possible to define a specific behavior for a particular constant of the enum which overrides the default behavior of the enum, this technique is known as constant specific body. Suppose three piano students - John, Ben and Luke - are defined in an enum named PianoClass, as follows:...

A typeglob *foo holds references to the contents of global variables with that name: $foo, @foo, $foo, &foo, etc. You can access it like an hash and assign to manipulate the symbol tables directly (evil!). use v5.10; # necessary for say our $foo = "foo"; our $bar; say ref *foo{SCAL...

open(my $fh, '<', "/some/path") or die $!; my @ary = <$fh>; When evaluated in list context, the diamond operator returns a list consisting of all the lines in the file (in this case, assigning the result to an array supplies list context). The line terminator is retained, and ...

XE2 program CrossPlatformHelloWorld; uses FMX.Dialogs; {$R *.res} begin ShowMessage('Hello world!'); end. Most of the Delphi supported platforms (Win32/Win64/OSX32/Android32/iOS32/iOS64) also support a console so the WriteLn example fits them well. For the platforms that require...

When Intel designed the original x86, the 8086 (and 8088 derivative), they included Segmentation to allow the 16-bit processor to access more than 16 bits worth of address. They did this by making the 16-bit addresses be relative to a given 16-bit Segment Register, of which they defined four: Code S...

AnchorPane a is a layout that allows placing the content at a specific distance from it's sides. There are 4 methods for setting and 4 methods for getting the distances in AnchorPane. The first parameter of these methods is the child Node. The second parameter of the setters is the Double value to ...

TextInputDialog allows the to ask the user to input a single String. TextInputDialog dialog = new TextInputDialog("42"); dialog.setHeaderText("Input your favourite int."); dialog.setTitle("Favourite number?"); dialog.setContentText("Your favourite int: ");...

$ mkdir hello-world $ cd hello-world $ tns create hello-world --ng $ tns platform add android #You can only add ios on an OSX machine Then ensure you have a device connected or an emulator running (if you don't, the default emulator should start or an error will be raised. I would recommend ge...

To start a bibliography you need to define your sources. Create a database file (like sources.bib) and include some content: @book{Doe1993, Author = {John Doe}, Publisher = {Earth University}, Title = {Creating a bibliography with biber}, Year = {1993}} You can then include y...

Microsoft Access is an Application Generator for developing databases and data-driven applications, primarily for local use. Microsoft Access consists of two main elements: A Relational Database Management System (RDBMS) that combines the Microsoft Jet Database Engine (Access 2003 and earler) or ...

Related to Monads are F# computation expressions (CE). A programmer typically implements a CE to provide an alternative approach to chaining Monads, ie instead of this: let v = m >>= fun x -> n >>= fun y -> return_ (x, y) You can write this: let v = ce { let! x = m ...

Most programming languages, including F#, evaluate computations immediately in accord with a model called Strict Evaluation. However, in Lazy Evaluation, computations are not evaluated until they are needed. F# allows us to use lazy evaluation through both the lazy keyword and sequences. // define ...

F#, like most programming languages, uses Strict Evaluation by default. In Strict Evaluation, computations are executed immediately. In contrast, Lazy Evaluation, defers execution of computations until their results are needed. Moreover, the results of a computation under Lazy Evaluation are cached,...

In Emacs, file has the same meaning as in the operating system, and is used for permanent storage of data. A buffer is the internal representation of a file being edited. Files can be read into buffers using C-x C-f, and buffers can be written to files using C-x C-s (save file at its current locatio...

Emacs's user interface uses terms that were coined early and can be unsettling to users used to a more modern terminology. Frame In Emacs, what is otherwise called a window (the area of the display used by a program) is called a frame. Emacs starts using one frame, though additional frames may b...

Sometimes it is desirable to evaluate a nullable expression in an if-else fashion. The elvis operator, ?:, can be used in Kotlin for such a situation. For instance: val value: String = data?.first() ?: "Nothing here." The expression above returns "Nothing here" if data?.firs...