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You are allowed to implement custom exceptions that can be thrown just like any other exception. This makes sense when you want to make your exceptions distinguishable from other errors during runtime. In this example we will create a custom exception for clear handling of problems the application ...

In normal mode: ~ inverts the case of the character under the cursor, gu{motion} lowercases the text covered by {motion}, gU{motion} uppercases the text covered by {motion} Example (^ marks the cursor position): Lorem ipsum dolor sit amet. ^ Lorem ipSum dolor sit amet. ~ Lorem...

If your code encounters a condition it doesn't know how to handle, such as an incorrect parameter, it should raise the appropriate exception. def even_the_odds(odds): if odds % 2 != 1: raise ValueError("Did not get an odd number") return odds + 1

Use try...except: to catch exceptions. You should specify as precise an exception as you can: try: x = 5 / 0 except ZeroDivisionError as e: # `e` is the exception object print("Got a divide by zero! The exception was:", e) # handle exceptional case x = 0 final...

Sometimes you want to catch an exception just to inspect it, e.g. for logging purposes. After the inspection, you want the exception to continue propagating as it did before. In this case, simply use the raise statement with no parameters. try: 5 / 0 except ZeroDivisionError: print(&quo...

In the process of handling an exception, you may want to raise another exception. For example, if you get an IOError while reading from a file, you may want to raise an application-specific error to present to the users of your library, instead. Python 3.x3.0 You can chain exceptions to show how t...

Exception handling occurs based on an exception hierarchy, determined by the inheritance structure of the exception classes. For example, IOError and OSError are both subclasses of EnvironmentError. Code that catches an IOError will not catch an OSError. However, code that catches an EnvironmentErr...

Exceptions are just regular Python objects that inherit from the built-in BaseException. A Python script can use the raise statement to interrupt execution, causing Python to print a stack trace of the call stack at that point and a representation of the exception instance. For example: >>&gt...

App.xaml.cs file (App.xaml file is default, so skipped) using Xamrin.Forms namespace NavigationApp { public partial class App : Application { public static INavigation GlobalNavigation { get; private set; } public App() { InitializeComponent()...

To find some number (more than one) of largest or smallest values of an iterable, you can use the nlargest and nsmallest of the heapq module: import heapq # get 5 largest items from the range heapq.nlargest(5, range(10)) # Output: [9, 8, 7, 6, 5] heapq.nsmallest(5, range(10)) # Output: [...

When the last parameter of a function is a closure func loadData(id: String, completion:(result: String) -> ()) { // ... completion(result:"This is the result data") } the function can be invoked using the Trailing Closure Syntax loadData("123") { result in ...

Sometimes you want to do something with the exception you catch (like write to log or print a warning) and let it bubble up to the upper scope to be handled. To do so, you can rethrow any exception you catch: try { ... // some code here } catch (const SomeException& e) { std::cout &l...

if ([object respondsToSelector:@selector(someOptionalMethodInProtocol:)]) { [object someOptionalMethodInProtocol:argument]; }

Move Blue to the beginning of the array: NSMutableArray *myColors = [NSMutableArray arrayWithObjects: @"Red", @"Green", @"Blue", @"Yellow", nil]; NSUInteger fromIndex = 2; NSUInteger toIndex = 0; id blue = [[[self.array objectAtIndex:fromIndex] retain]...

This example will guide you through setting up a back end serving an a Hello World HTML page. Installing Requirements Order matters for this step! sudo apt-get install apache2 Setting up the HTML Apache files live in /var/www/html/. Lets quickly get there. Make sure you're in your root ...

In Swift, we can exponentiate Doubles with the built-in pow() method: pow(BASE, EXPONENT) In the code below, the base (5) is set to the power of the exponent (2) : let number = pow(5.0, 2.0) // Equals 25

Due to Node's asynchronous nature, creating or using a directory by first: checking for its existence with fs.stat(), then creating or using it depending of the results of the existence check, can lead to a race condition if the folder is created between the time of the check and the time of ...

Exporting a macro to allow other modules to use it: #[macro_export] // ^~~~~~~~~~~~~~~ Think of it as `pub` for macros. macro_rules! my_macro { (..) => {..} } Using macros from other crates or modules: #[macro_use] extern crate lazy_static; // ^~~~~~~~~~~~ Must add this in ord...

If you need to match characters that are a part of the regular expression syntax you can mark all or part of the pattern as a regex literal. \Q marks the beginning of the regex literal. \E marks the end of the regex literal. // the following throws a PatternSyntaxException because of the un-close...

-- Create an index for column 'name' in table 'my_table' CREATE INDEX idx_name ON my_table(name);