Tutorial by Examples: d

When you create an argparse ArgumentParser() and run your program with '-h' you get an automated usage message explaining what arguments you can run your software with. By default, positional arguments and conditional arguments are separated into two categories, for example, here is a small script ...

The main app file loads the routes file where routes are defined. app.js var express = require('express'); var app = express(); app.use('/', require('./routes')); app.listen('3000'); routes.js var router = require('express').Router(); router.get('/', function(req, res) { res.sen...

Middleware is executed prior to the route execution and can decide whether to execute the router according to the URL. var router = require('express').Router(); router.use(function (req, res, next) { var weekDay = new Date().getDay(); if (weekDay === 0) { res.send('Web is clos...

Use associated type when there is a one-to-one relationship between the type implementing the trait and the associated type. It is sometimes also known as the output type, since this is an item given to a type when we apply a trait to it. Creation trait GetItems { type First; // ^~~~ d...

Say you have implemented some logic to detect attempts to modify an object in the database while the client that submitted changes didn't have the latest modifications. If such case happens, you raise a custom exception ConfictError(detailed_message). Now you want to return an HTTP 409 (Confict) st...

Use the maxlen parameter while creating a deque to limit the size of the deque: from collections import deque d = deque(maxlen=3) # only holds 3 items d.append(1) # deque([1]) d.append(2) # deque([1, 2]) d.append(3) # deque([1, 2, 3]) d.append(4) # deque([2, 3, 4]) (1 is removed because i...

Creating empty deque: dl = deque() # deque([]) creating empty deque Creating deque with some elements: dl = deque([1, 2, 3, 4]) # deque([1, 2, 3, 4]) Adding element to deque: dl.append(5) # deque([1, 2, 3, 4, 5]) Adding element left side of deque: dl.appendleft(0) # deque([0, 1, 2, ...

Methods can be set on Schemas to help doing things related to that schema(s), and keeping them well organized. userSchema.methods.normalize = function() { this.name = this.name.toLowerCase(); }; Example usage: erik = new User({ 'name': 'Erik', 'password': 'pass' }); erik.nor...

Often times you will see an exception Anti forgery token is meant for user "" but the current user is "username" This is because the Anti-Forgery token is also linked to the current logged-in user. This error appears when a user logs in but their token is still linked to bein...

#Post to pagerduty.com notification pagerduty { post = https://events.pagerduty.com/generic/2010-04-15/create_event.json contentType = application/json runOnActions = false body = `{ "service_key": "myservicekey", "incident_key": {{.|jso...

In many other languages, if you run the following (Java example) if("asgdsrf" == 0) { //do stuff } ... you'll get an error. You can't just go comparing strings to integers like that. In Python, this is a perfectly legal statement - it'll just resolve to False. A common gotcha ...

<div tabindex="0">Some button</div> Note: Try to use a native HTML button or an a tag where appropriate.

<button tabindex="-1">This button will not be reachable by tab</button> The element will be removed from the tabbing order but will still be focusable.

<div tabindex="2">Second</div> <div tabindex="1">First</div> Positive values will insert the element at the tabbing order position of its respective value. Elements without preference (i.e. tabindex="0" or native elements such as button and a...

We can optimize a simple xor function for only architectures that support unaligned reads/writes by creating two files that define the function and prefixing them with a build constraint (for an actual example of the xor code which is out of scope here, see crypto/cipher/xor.go in the standard libra...

Just some methods of an object can be mocked using spy() of mockito. For example, imagine that method class requires some web service to work. public class UserManager { List<User> users; public UserManager() { user = new LinkedLisk<User>(); } ...

go() method The go() method loads a specific URL from the history list. The parameter can either be a number which goes to the URL within the specific position (-1 goes back one page, 1 goes forward one page), or a string. The string must be a partial or full URL, and the function will go to the f...

The spacing should be even and uniform throughout. Improper indentation can cause an IndentationError or cause the program to do something unexpected. The following example raises an IndentationError: a = 7 if a > 5: print "foo" else: print "bar" print "done&qu...

This basic code will launch a "Hello world" GUI window using PyQt4: import sys from PyQt4 import QtGui # create instance of QApplication app = QtGui.QApplication(sys.argv) # create QLabel, without parent it will be shown as window label = QtGui.QLabel('Hello world!') label.show(...

The hashlib module allows creating message digest generators via the new method. These generators will turn an arbitrary string into a fixed-length digest: import hashlib h = hashlib.new('sha256') h.update(b'Nobody expects the Spanish Inquisition.') h.digest() # ==> b'.\xdf\xda\xdaVR[\x12\...