Tutorial by Examples: el

Relational operators check if a specific relation between two operands is true. The result is evaluated to 1 (which means true) or 0 (which means false). This result is often used to affect control flow (via if, while, for), but can also be stored in variables. Equals "==" Checks whether...

A table may be joined to itself, with different rows matching each other by some condition. In this use case, aliases must be used in order to distinguish the two occurrences of the table. In the below example, for each Employee in the example database Employees table, a record is returned containi...

Ruby has three access levels. They are public, private and protected. Methods that follow the private or protected keywords are defined as such. Methods that come before these are implicitly public methods. Public Methods A public method should describe the behavior of the object being created. T...

The simplest way to iterate over a file line-by-line: with open('myfile.txt', 'r') as fp: for line in fp: print(line) readline() allows for more granular control over line-by-line iteration. The example below is equivalent to the one above: with open('myfile.txt', 'r') as fp: ...

str.split(sep=None, maxsplit=-1) str.split takes a string and returns a list of substrings of the original string. The behavior differs depending on whether the sep argument is provided or omitted. If sep isn't provided, or is None, then the splitting takes place wherever there is whitespace. Howe...

The <select> element generates a drop-down menu from which the user can choose an option. <select name=""> <option value="1">One</option> <option value="2">Two</option> <option value="3">Three</option> ...

The basic syntax of SELECT with WHERE clause is: SELECT column1, column2, columnN FROM table_name WHERE [condition] The [condition] can be any SQL expression, specified using comparison or logical operators like >, <, =, <>, >=, <=, LIKE, NOT, IN, BETWEEN etc. The following ...

SELECT PhoneNumber, Email, PreferredContact FROM Customers This statement will return the columns PhoneNumber, Email, and PreferredContact from all rows of the Customers table. Also the columns will be returned in the sequence in which they appear in the SELECT clause. The re...

Create a new file called hello.sh with the following content and give it executable permissions with chmod +x hello.sh. Execute/Run via: ./hello.sh #!/usr/bin/env bash # Note that spaces cannot be used around the `=` assignment operator whom_variable="World" # Use printf to sa...

A delegate is a common design pattern used in Cocoa and CocoaTouch frameworks, where one class delegates responsibility for implementing some functionality to another. This follows a principle of separation of concerns, where the framework class implements generic functionality while a separate dele...

The <article> element contains self-contained content like articles, blog posts, user comments or an interactive widget that could be distributed outside the context of the page, for example by RSS. When article elements are nested, the contents of the inner article node should be related t...

The <main> element contains the main content for your web page. This content is unique to the individual page, and should not appear elsewhere on the site. Repeating content like headers, footers, navigation, logos, etc., is placed outside the element. The <main> element should only e...

With a Frame When you know the exact dimensions you want to set for your label, you can initialize a UILabel with a CGRect frame. Swift let frame = CGRect(x: 0, y: 0, width: 200, height: 21) let label = UILabel(frame: frame) view.addSubview(label) Objective-C CGRect frame = CGRectMake(0, 0,...

The <nav> element is primarily intended to be used for sections that contain main navigation blocks for the website, this can include links to other parts of the web page (e.g. anchors for a table of contents) or other pages entirely. Inline items The following will display an inline set of ...

Interactive Shell The Bash shell is commonly used interactively: It lets you enter and edit commands, then executes them when you press the Return key. Many Unix-based and Unix-like operating systems use Bash as their default shell (notably Linux and macOS). The terminal automatically enters an int...

git rm filename To delete the file from git without removing it from disk, use the --cached flag git rm --cached filename

# First falsy element or last element if all are truthy: reduce(lambda i, j: i and j, [100, [], 20, 10]) # = [] reduce(lambda i, j: i and j, [100, 50, 20, 10]) # = 10 # First truthy element or last element if all falsy: reduce(lambda i, j: i or j, [100, [], 20, 0]) # = 100 reduce(la...

When it comes to adding/removing channels to/from your channel groups, you need to have must have the manage permission for those channel groups. But you should never grant clients the permission to manage the channel groups that they will subscribe to. If they did, then they could add any channel t...

First, install Node.js for your platform. In this example we'll create an HTTP server listening on port 1337, which sends Hello, World! to the browser. Note that, instead of using port 1337, you can use any port number of your choice which is currently not in use by any other service. The http mod...

Type the following code into your terminal, then press Enter: echo "Hello World" This will produce the following output: Hello World