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Study_Material/Cheatsheets/Backend/Django.py

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+# *****************************************************************************
+# CODING STYLE > MAKING YOUR CODE READABLE
+# *****************************************************************************
+
+
+# 1. Avoid abbreviating variable names.
+# 2. Write out your function argument names.
+# 3. Document your classes and methods.
+# 4. Comment your code.
+# 5. Refactor repeated lines of code into reusable functions or methods.
+# 6. Keep functions and methods short. A good rule of thumb is that scrolling
+# should not be necessary to read an entire function or method.
+
+# TIP: Use Flake8 for Checking Code Quality.
+
+
+# *****************************************************************************
+# CODING STYLE > THE WORD ON IMPORTS
+# *****************************************************************************
+
+
+# Imports should be grouped in the following order:
+
+# 1. Standard library imports.
+# 2. Core Django imports.
+# 3. Third-party app imports.
+# 4. Imports from your apps.
+
+# Use explicit relative imports.
+# Avoid using import *
+
+
+# *****************************************************************************
+# CODING STYLE > OTHERS
+# *****************************************************************************
+
+
+# Use underscores in URL pattern names rather than dashes.
+
+# *****************************************************************************
+# CODING STYLE > DATABASE
+# *****************************************************************************
+
+# 1.Register your app in admin file in your app folder to use admin panel in django
+# 2.Create a superuser using command python manage.py createsuperuser
+# 3.Remember to migrate after you change anything in your models.py file
+# 4.Use /admin/ page to add data in your tables for testing purpose
+
+
+# *****************************************************************************
+# Deployment
+# *****************************************************************************
+
+
+# add your media, database, venv, __pycache__ to the .gitignore (there is a compelete list that you can find here: https://github.com/jpadilla/django-project-template/blob/master/.gitignore)
+# keep migration files in the git (you will need to migrate them in target server)
+# don't run "makemigrations" in the target server (you will need to just run "migrate")
+# $ pip freeze > requirements.txt
+# make appropriate changes in your project settings.py file (change DEBUG to False and etc)
+# push your code to your git-server
+# pull your code in your target server
+# give right permissions to the web-server (e.g. $ chown www-data:www-data -R /var/www/myproject)
+# make a new venv in the target server and activate it
+# $ sudo pip install -r requirements.txt
+# sudo ./venv/bin/python3 manage.py migrate
+# restart your web-server (in case of apache: $ sudo service apache2 restart)
+
+
+# *****************************************************************************
+# DJANGO-ADMIN
+# *****************************************************************************
+
+
+django-admin check                       # Checks the entire django project for potential problems
+django-admin changepassword <username>   # Allows changing a user’s password. It prompts you to enter a new password twice for the given user.
+django-admin clearsessions               # Can be run as a cron job or directly to clean out expired sessions.
+django-admin collectstatic               # Helps to collect all the static files in the one mentioned directory
+django-admin createsuperuser             # Creates a superuser account (a user who has all permissions).
+django-admin compilemessages             # Compiles .po files to .mo files for use with builtin gettext support
+django-admin createcachetable            # Creates the tables needed to use the SQL cache backend.
+django-admin dbshell                     # Runs the command-line client for specified database, or the default database if none is provided.
+django-admin diffsettings                # Displays differences between the current settings.py and Django's default settings.
+django-admin dumpdata                    # Output the contents of the database as a fixture of the given format (using each model's default manager unless --all is specified).
+django-admin flush                       # Removes ALL DATA from the database, including data added during migrations. Does not achieve a "fresh install" state.
+django-admin inspectdb                   # Introspects the database tables in the given database and outputs a Django model module.
+django-admin loaddata                    # Installs the named fixture(s) in the database.
+django-admin makemessages                # Runs over the entire source tree of the current directory and pulls out all strings marked for translation. It creates (or updates) a message file in the conf/locale (in the django tree) or locale (for projects and applications) directory. You must run this command with one of either the --locale, --exclude, or --all options.
+django-admin help                        # display usage information and a list of the commands provided by each application
+django-admin makemigrations              # create new migrations to the database based on the changes detected in the models
+django-admin migrate                     # synchronize the database state with your current state project models and migrations
+django-admin remove_stale_contenttypes   # Deletes stale content types (from deleted models) in your database.y.
+django-admin runserver <port>            # start the development webserver at 127.0.0.1 with the port <port> default 8000
+django-admin sendtestemail               # Sends a test email to the email addresses specified as arguments.
+django-admin shell                       # Runs a Python interactive interpreter. Tries to use IPython or bpython, if one of them is available. Any standard input is executed as code.
+django-admin showmigrations              # Shows all available migrations for the current project.
+django-admin sqlflush                    # Returns a list of the SQL statements required to return all tables in the database to the state they were in just after they were installed.
+django-admin sqlmigrate                  # Prints the SQL statements for the named migration.
+django-admin sqlsequencereset            # Prints the SQL statements for resetting sequences for the given app name(s).
+django-admin squashmigrations            # Squashes an existing set of migrations (from first until specified) into a single new one.
+django-admin startapp <Appname>          # create a new django application with the specified name
+django-admin startproject <ProjectName>  # create a new project directory structure
+django-admin testserver                  # Runs a development server with data from the given fixture(s).
+django-admin version                     # display the current django version
+
+
+# *****************************************************************************
+# Starting a django project in python3
+# *****************************************************************************
+
+
+# 1. $ curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py; python3 get-pip.py						
+# 2. $ pip install virtualenv
+# 3. $ mkdir django-projects
+# 4. $ cd django-projects  
+# 5. $ virtualenv venv 								
+# 6. $ source venv/bin/activate	
+# 7. $ pip install django							
+# 8. $ django-admin startproject myproject
+# 9. $ django-admin startapp myapp
+# 10. $ python manage.py runserver

Study_Material/Cheatsheets/Backend/Express.js

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+/* *******************************************************************************************
+ * API
+ * http://expressjs.com/en/api.html
+ * ******************************************************************************************* */
+`npm i express --save` or`yarn add -D express``(-D saves it as a dev dependency)`
+`yarn add -D @types/express``(Installing for TS)`
+
+const express = require("express"); // Importing the express library.
+const app = express(); // Intializing the imported express application
+
+/* *******************************************************************************************
+ * GLOBAL OBJECTS
+ * http://expressjs.com/en/api.html#express.json
+ * ******************************************************************************************* */
+
+```Methods```;
+
+`express.json([options]);`
+
+options: `
+inflate                   // to manage the deflated bodies like enabling and disabling
+
+limit                     // Controls the maximum request body size.
+
+reviver                   // It is passed directly to JSON.parse as an second argument
+
+type                      // This is used to determine the type of middleware will parse
+
+verify                    // It is an undefined function which used to verify the middleware parsing.
+
+`;
+
+`express.raw([options]);`
+
+options: `
+inflate                   // to manage the deflated bodies like enabling and disabling
+
+limit                     // Controls the maximum request body size.
+
+type                      // This is used to determine the type of middleware will parse
+
+verify                    // It is an undefined function which used to verify the middleware parsing.
+`;
+
+`express.Router([options]);`
+
+options: `
+caseSensitive             //Enables case sensitivity
+
+mergeParams               //if param names of child and parent are conflicted then the child takes the precedence
+
+strict                    // Enables Strict routing
+`;
+
+`express.static(root, [options]);`
+
+options: `
+dotfiles                 // determines how dotfiles are used
+
+etag                     // Operates etag generation
+
+extensions               // Operates file extension fallback
+
+fallthrough              //	Enable or disable the immutable directive in the Cache-Control response header
+
+index                    // sends the specified directory index file
+
+LastModified             // sets the Last-Modified header to the last modified date
+
+setHeaders               // Function for setting HTTP headers to serve with the file
+`;
+
+`express.text([options]);`
+
+options: `
+defaultCharset          // Sets the default charset for the text context.
+
+inflate                 // to manage the deflated bodies like enabling and disabling
+
+limit                   // Controls the maximum request body size.
+
+type                    // This is used to determine the type of middleware will parse
+
+verify                  // It is an undefined function which used to verify the middleware parsing.
+`;
+
+`express.urlencoded([options]);`
+
+options: `
+extended                // it allows to choose between parsing the URL-encoded data or the qs library
+
+parameterLimit          // It controls the no of params.
+
+inflate                 // to manage the deflated bodies like enabling and disabling
+
+limit                   // Controls the maximum request body size.
+
+type                    // This is used to determine the type of middleware will parse
+
+verify                  // It is an undefined function which used to verify the middleware parsing.
+`;
+
+```Application`````;
+Properties```app.local`;
+
+`app.locals.title = "My Cheatsheet";
+
+console.dir(app.locals.title)`;                     `// Creating objects with local variables`
+
+app.mountpath`
+
+``app.mountpath``const admin = express()
+admin.get('/', function(req,res){
+    console.log(admin.mountpath)
+    res.send('Admin Homepage')
+})                            
+
+app.use('<admin dir>', admin)`;                    `// Mounting a sub - app`
+
+``Event``
+
+`admin.on('mount', (parent){
+    console.log('Admin Mounted')
+})`                                                `// Mounting on a parent app`
+
+``Methods``
+`app.get('/', function(req, res){
+    res.send('GET request to message')
+})`                                               `// get requests to the specified path`
+
+`app.post('/', function(req,res){
+    res.send('POST request to a webpage')
+})`                                               `// post request to the specified path`
+
+`app.put('/', function(req,res){
+    res.send('PUT request to a webpage')
+})`                                               `// post request to the specified path`
+
+`app.delete('/', function(req,res){
+    res.send('DELETE request to a webpage')
+})`                                               `// delete request to the specified path`
+
+`app.all('/', function(req,res,next){
+    console.log('Accessing the secret section....')
+    next()
+})`                                               `// Routing all types of HTTP request`
+
+`app.param('user', function(req,res,next){
+    User.find(id, function(err, user){
+        if(err){
+            next(err)
+        } else if (user){
+            req.user = user
+            next()
+        } else {
+            next(new Error('Failed to load user'))
+        }
+    })
+})`                                               `// Adding callback trigger to route parameters`
+
+`app.use(function(req,res,next){
+    res.send('Hey There!')
+})`                                               `// To Invoke the middleware layer that you want to add`
+
+```Request```
+``Methods``
+
+`req.get('content-type')`                         `// Returns the specified HTTP req header`
+
+`req.accepts('html')`                             `// Checks if the specified content types are available or not`
+
+`req.is('json')`                                  `// Requests the matching content-type`
+
+`var range = req.range(1000)
+if (range.type === 'bytes'){
+    range.forEach(function(r){
+        // Your code
+    })
+}`                                                `// Range header parser`
+
+``Properties``
+
+`req.param('name')`                               `// Requests the param name when present`
+
+`app.post('/', function (req, res, next) {
+    console.log(req.body)
+    res.json(req.body)
+})`                                                `// Data submitted in the request body`
+
+`console.dir(req.cookies.name)`                    `// Contains cookies sent by the request`
+
+`console.dir(req.query.q)`                         `// Query string parameter in the route`
+
+`console.log(req.route)
+res.send('GET')`                                   `// Outputs all the layer, methods, path`
+
+`console.dir(req.signedCookies.user)`              `// Logs all the signed cookies sent by the request`
+
+
+```Response```
+``Methods``
+
+`res.redirect('https://google.com')`               `// Redirects to the intended page`
+
+`res.send({message: 'Awesome Stuffs'})`            `// Response to the webpage` 
+
+`res.json({alert: 'awesomecheatsheets'})`          `// Response in JSON type`
+
+`const file = req.params.name;
+res.sendFile(file, options, function(err){
+    if(err){
+        next(err)
+    }else{
+        console.log('Sent:', file)
+    }
+})`                                                `// Sends file to the intended path`
+
+`res.render('index')`                              `// Rendering the intended file`
+
+```BodyParser```
+
+`const BodyParser = require('body-parser')
+app.use(BodyParser.json())
+app.use(BodyParser.urlencoded({
+    extended: true
+}))`                                               `// Parses incoming request bodies`