Tutorial by Examples: g

This query gets all overlapping appointments from six to ten. Appointment.objects.filter(time_span__overlap=(6, 10))

This query selects all books with any rating greater than or equal to four. maybe_good_books = Books.objects.filter(ratings_range__contains=(4, None))

the timedelta module comes in handy to compute differences between times: from datetime import datetime, timedelta now = datetime.now() then = datetime(2016, 5, 23) # datetime.datetime(2016, 05, 23, 0, 0, 0) Specifying time is optional when creating a new datetime object delta = now-then ...

To remove extraneous packages (packages that are installed but not in dependency list) run the following command: npm prune To remove all dev packages add --production flag: npm prune --production More on it

To generate a list (tree view) of currently installed packages, use npm list ls, la and ll are aliases of list command. la and ll commands shows extended information like description and repository. Options The response format can be changed by passing options. npm list --json json - Sh...

When using a VCS such as Git or SVN, there are some secret data that must never be versioned (whether the repository is public or private). Among those data, you find the SECRET_KEY setting and the database password. A common practice to hide these settings from version control is to create a file...

Since npm itself is a Node.js module, it can be updated using itself. If OS is Windows must be running command prompt as Admin npm install -g npm@latest If you want to check for updated versions you can do: npm outdated In order to update a specific package: npm update <package name>...

A closure is the PHP equivalent of an anonymous function, eg. a function that does not have a name. Even if that is technically not correct, the behavior of a closure remains the same as a function's, with a few extra features. A closure is nothing but an object of the Closure class which is create...

It is possible, inside a closure, to use an external variable with the special keyword use. For instance: <?php $quantity = 1; $calculator = function($number) use($quantity) { return $number + $quantity; }; var_dump($calculator(2)); // Shows "3" You can go further by ...

As seen previously, a closure is nothing but an instance of the Closure class, and different methods can be invoked on them. One of them is bindTo, which, given a closure, will return a new one that is bound to a given object. For example: <?php $myClosure = function() { echo $this->p...

Let's consider this example: <?php $myClosure = function() { echo $this->property; }; class MyClass { public $property; public function __construct($propertyValue) { $this->property = $propertyValue; } } $myInstance = new MyClass('Hello world...

Since PHP7, it is possible to bind a closure just for one call, thanks to the call method. For instance: <?php class MyClass { private $property; public function __construct($propertyValue) { $this->property = $propertyValue; } } $myClosure = function() ...

We define two sets a and b >>> a = {1, 2, 2, 3, 4} >>> b = {3, 3, 4, 4, 5} NOTE: {1} creates a set of one element, but {} creates an empty dict. The correct way to create an empty set is set(). Intersection a.intersection(b) returns a new set with elements present in bot...

This example creates a simple 1-column repeater that displays a list of numbers, one per repeater item. Markup: <asp:Repeater ID="Repeater1" runat="server"> <ItemTemplate> <%# Container.DataItem.ToString() %> </ItemTemplate> </Repe...

Even though Python natively supports big integers, taking the nth root of very large numbers can fail in Python. x = 2 ** 100 cube = x ** 3 root = cube ** (1.0 / 3) OverflowError: long int too large to convert to float When dealing with such large integers, you will need to use a custom f...

The git commit command does a few things: Create blobs and trees to represent your project directory - stored in .git/objects Creates a new commit object with your author information, commit message, and the root tree from step 1 - also stored in .git/objects Updates the HEAD ref in .git/HEAD t...

When you run git checkout on a commit (specified by hash or ref) you're telling git to make your working directory look like how it did when the snapshot was taken. Update the files in the working directory to match the tree inside the commit Update HEAD to point to the specified hash or ref ...

Running git reset --hard moves refs to the specified hash/ref. Moving MyBranch to b8dc53: $ git checkout MyBranch # moves HEAD to MyBranch $ git reset --hard b8dc53 # makes MyBranch point to b8dc53

Running git checkout -b <refname> will create a new ref that points to the current commit. $ cat .git/head 1f324a $ git checkout -b TestBranch $ cat .git/refs/heads/TestBranch 1f324a

The reduce function can be used to sum the elements in a list. (reduce '+ '(1 2 3 4)) ;;=> 10 By default, reduce performs a left-associative reduction, meaning that the sum 10 is computed as (+ (+ (+ 1 2) 3) 4) The first two elements are summed first, and then that result (3) is added to...