Tutorial by Examples: n

Add the following code (known as the "JavaScript tracking snippet") to your site's templates. The code should be added before the closing tag, and the string 'UA-XXXXX-Y' should be replaced with the property ID (also called the "tracking ID") of the Google Analytics property yo...

CSS body { counter-reset: item-counter; } .item { counter-increment: item-counter; } .item:before { content: counter(item-counter, upper-roman) ". "; /* by specifying the upper-roman as style the output would be in roman numbers */ } HTML <div class='item'>Item...

CSS body { counter-reset: item-counter; /* create the counter */ } .item { counter-increment: item-counter; /* increment the counter every time an element with class "item" is encountered */ } .item-header:before { content: counter(item-counter) ". "; /* print the v...

The begin block is a control structure that groups together multiple statements. begin a = 7 b = 6 a * b end A begin block will return the value of the last statement in the block. The following example will return 3. begin 1 2 3 end The begin block is useful for conditi...

In Drupal 7 and lower, your configuration is probably stored using the Features module. To update a feature with changes from the databases use this command: drush features-update [feature-name] // e.g. drush features-update content_type_news You can also use this shorthand: drush fu [feature-n...

function createNewFolderInGoogleDrive(folderName) { return DriveApp.createFolder(folderName); } Use function createNewFolderInGoogleDrive to create folder named Test folder in a Google Drive root: var newFolder = createNewFolderInGoogleDrive('Test folder'); newFolder has Class Folder typ...

A HTTP 500 Internal Server Error is a general message meaning that the server encountered something unexpected. Applications (or the overarching web server) should use a 500 when there's an error processing the request - i.e. an exception is thrown, or a condition of the resource prevents the proces...

HTTP 404 Not Found means that the server couldn't find the path using the URI that the client requested. HTTP/1.1 404 Not Found Most often, the requested file was deleted, but sometimes it can be a document root misconfiguration or a lack of permissions (though missing permissions more frequentl...

Use 403 Forbidden when a client has requested a resource that is inaccessible due to existing access controls. For example, if your app has an /admin route that should only be accessible to users with administrative rights, you can use 403 when a normal user requests the page. GET /admin HTTP/1.1 ...

Iterable can be anything for which items are received one by one, forward only. Built-in Python collections are iterable: [1, 2, 3] # list, iterate over items (1, 2, 3) # tuple {1, 2, 3} # set {1: 2, 3: 4} # dict, iterate over keys Generators return iterables: def foo(): # foo ...

s = {1, 2, 3} # get every element in s for a in s: print a # prints 1, then 2, then 3 # copy into list l1 = list(s) # l1 = [1, 2, 3] # use list comprehension l2 = [a * 2 for a in s if a > 2] # l2 = [6]

Use unpacking to extract the first element and ensure it's the only one: a, = iterable def foo(): yield 1 a, = foo() # a = 1 nums = [1, 2, 3] a, = nums # ValueError: too many values to unpack

Start with iter() built-in to get iterator over iterable and use next() to get elements one by one until StopIteration is raised signifying the end: s = {1, 2} # or list or generator or even iterator i = iter(s) # get iterator a = next(i) # a = 1 b = next(i) # b = 2 c = next(i) # raises S...

def gen(): yield 1 iterable = gen() for a in iterable: print a # What was the first item of iterable? No way to get it now. # Only to get a new iterator gen()

You can write the default protocol implementation for a specific class. protocol MyProtocol { func doSomething() } extension MyProtocol where Self: UIViewController { func doSomething() { print("UIViewController default protocol implementation") } } class M...

Generic classes can be inherited: // Models class MyFirstModel { } class MySecondModel: MyFirstModel { } // Generic classes class MyFirstGenericClass<T: MyFirstModel> { func doSomethingWithModel(model: T) { // Do something here } } class MySecondGe...

Setting up settings.py from django.utils.translation import ugettext_lazy as _ USE_I18N = True # Enable Internationalization LANGUAGE_CODE = 'en' # Language in which original texts are written LANGUAGES = [ # Available languages ('en', _("English")), ('de', _("Germ...

In order to efficiently handle cycle detection, we consider each node as part of a tree. When adding an edge, we check if its two component nodes are part of distinct trees. Initially, each node makes up a one-node tree. algorithm kruskalMST'(G: a graph) sort G's edges by their value MST ...

The above forest methodology is actually a disjoint-set data structure, which involves three main operations: subalgo makeSet(v: a node): v.parent = v <- make a new tree rooted at v subalgo findSet(v: a node): if v.parent == v: return v return findSet(v.parent...

We can do two things to improve the simple and sub-optimal disjoint-set subalgorithms: Path compression heuristic: findSet does not need to ever handle a tree with height bigger than 2. If it ends up iterating such a tree, it can link the lower nodes directly to the root, optimizing future trav...