Django – Part 2

Intro

Django’s slogan is “The web framework for perfectionists with deadlines.” It accomplishes this in a few different ways, forced compartmentalization, built in development tools, and every feature you could ask for. Below we will discuss how to get started, and how see how Django handles MVC.

Getting started:

You first want to setup a virtual env. I am using Anaconda, so I would type in:

  1. conda create –name <your env name> django
  2. source activate <your env name>

Then you would use Django’s great command line tools to create your first project:

  • django-admin startproject <your app name>

Once you the command above you will have your very first Django app. However it won’t do very much. You can execute the following command to run the application:

  • python manage.py runserver

As you can see its pretty boring and does not due much. Django is built around the idea of applications, being different modules in your over all application. These modules are separate from the main project and encapsulate the different features of your application. You create a Django app by then running:

  • python manage.py startapp <app name>

By running the command you get a new directory generated in your folder structure.

Getting started with MVC (MTV):

Dajango does not use the MVC design pattern per say, rather it uses the MTV design pattern. MTV stands for:

M – model : This is a simple python classes.

As you can see it is very easy to start building the inter model relationships. All models need to inherit from the Model class. This is all possible due to Djangos built in ORM. The ORM abstracts away the whole concept of having to work with a SQL DB, since it also provides a easy method revise your tables to reflect changes to your python models. This is simply done by using the:

  • python manage.py migrate
  • python manage.py make migrations < Dajango app name>

T – template : This is your html that displays model data through server side rendering.

Note that to serve these files, they need to be outside your main Django app, and they need to be reregistered in the Django settings file.

V – view : This is interestingly your controller.

As you can see above, you tie the data from your controller to your view by way of dictionaries. And tie your templates to your controllers to your views by specifying the url path name, and the file name.

A point of interest here, is that unlike some other frameworks your mapping a url to a method, rather then a whole class that contains different methods. This method mapping to is done using url.py files that exist both in the directory of the main project and the django app.

The main project directory:

The Django app:

As you can see your using regex, to find a specific url, then mapping it to a method. The main urls.py file contains the main urls for the whole project and imports the urls specifically for the Django app. Whereas the Django app just contains the sub urls for that particular app.

The “http://127.0.0.1:8000/first_app&#8221; would hit the “first_app” app, then it would then hit any of the sub urls stored in the Django app urls file.

As you can see Django is not that hard use at all, and in most ways is significantly easier then other frameworks, that don’t have all these built in features. In the next blog post I will be discussing Models, the Django admin console, and how the ORM handles model changes.

You can find part one here.

 

Intro to Python ? – Part 2

You can find Part 1 here.

Intro

In this part of the series we are going to cover the very basics of Python. You may be asking: “Its Python, how hard can it get ? Its just sudo code” well that is both true and false to a degree.

Variables

Python is a dynamically typed language, however it is strongly typed. This just means that you can set a variable to any sort of data type you want without declaring it first. However it doesn’t implicitly convert types for you.

Collections

Python also contains different types array like structures. And they are all get dynamically sized of course. You have Lists and Dictionaries, they all work the way you intuitively think do, coming from another programming language. The only new sort of collection type, you will encounter is the Tuple. A Tuple is pretty much the same thing as a List however they are immutable and can not contain repeats of the same value.

Control Flow

It’s pretty basic.

Loops

Python does not find “for” loops pythonic that is way it favors “For In” loops instead. maybe asking: “What if I just want to print something 3 times ? do I have to make a list with three elements ?” The answer is no, you can use a “generator” shown in the gists below. Python also has something called “list comprehension” its very nifty to write compact and concise code.

 

You can go here to find all the relevant code, in order.

Django – Part 1

Django_Reinhardt_(Gottlieb_07301)
Django Reinhardt a jazz legend

No I am not talking about this guy to the left.

I am actually talking about the web framework written in Python. Now the reason that I have even started learning this, is cause I wanted to see what all the hype is about. Plus I wanted to get a better understanding of the Python language its self.

Now I come from the world of Express.js which is kinda of like Flask, in terms of its bare-bones nature. So when I first saw Django I was reminded of ASP.NET, and Ruby on Rails. You might be thinking what sort of nonsnese is this kid spouting ? How the can he put two of the most loved opens sourced projects next to, Microsofts evil ways. And to that I respond with: A) Microsoft is not evil, and B) I say that since all three of these frameworks have so much built in functionality, that they become opaque. Opaque as in not transparent as in have to use for along time to really understand how they work.

Anyways this is a post letting you guys or gals out there know, I am going to be making a tutorial series as I start to learn the framework.

Yes I know that all my posts are starting to seem like tutorials or updates. I promise they will eventually be about something else 😅

Getting Started with Express.js

Intro

Raise your hand if you already know the MVC design pattern ! … oh right you can’t.

You can look at one of my previous blog posts here. Now that we have gotten that out of the way. Express.js provides an incredibly simplistic and transparent way to develop APIs for your applications. It’s one of the most popular frameworks to run on the Node.js platform.

You simply define your routes, define what you want to send out and pull in, and your golden 👍

Setting it up:

Routes:

Here you can see the route in question is just a slash. That means that when ever anyone hits the https://”your domain”/, this route gets triggered (since it is a GET request). Once the route gets triggered it executes the function, that has the “req”, and “res” variables. The “req” is your request object, and the “res” is your response object. You can put different things in the res object and it gets passed along to be rendered in HTML.

This same sort of logic can be applied to POST and PUT requests.

Folder Structures:

You can use a variety of different folder structures. What ever folder structure you use, make sure its suited for the type of app your going to be building. You can checkout an example over here.

And your done ! Easy as that. You may be thinking WTF is that really it ? Why do people want to use Express.js if this is it ? Well the answer is that the frame work does not lock you into, using any specific way of doing things. Therefor you can use any sort of authentication, object relational mapper, session manager, or data base you want.

You can find the best 40 packages most commonly used here.

Intro to Python ? – Part 1

Intro

You may have seen the title and been a bit surprised. In a previous post here, I said I don’t like Python. So you might be asking why I am even writing this. It’s cause I decided to give Python another shoot to wow me. Therefor I am going to start going into the cycle of learning a bit about it and then writing about it, and so on.

What is it ?

Its just a general purpose programming language.

What type of programming language is it really ?

It is a interpreted , dynamically typed, and strongly typed.

What can it do ?

Just like Java, C#, or C, it can do anything. That includes everything from Machine Learning to Desktop App Development.

What are it’s main selling points ?

  • Readable syntax to the point where, you can mistake it for pseudo code
  • Hugh and active community that supports it
  • Large selection of libraries
  • Large enterprises use it and actively contribute to it, such as Google, Reddit, The New York Times, and etc.

What are the draw backs ?

  • Its interpreted so it won’t be as fast as a compiled language
  • Far from the metal aka a thick layer of abstraction
  • No static typing
  • Object Oriented paradigm isn’t flushed out, for example there are no accesses modifiers on class variables (instance variables)
  • There are two different versions of language 2.7 and 3.x
    • Some libraries choose not to move to 3.x

 

MVC made easy

When I was first learning MVC I don’t have much to any experience programming for the web. I didn’t even now what the request response cycle was. The most programming experience I have ever had was printing interesting patterns using Java.

At the end of the day MVC is much more of an idea about how and why we should structure a program. For example when we write a web site that has your basic CRUD operations, you don’t want everything living in a single file that requires you to use the find functions to find your method.

So start separating out functionality, and at a very basic level we get a Model, View, and Controller. There for each of these things do something very specific. Most applications at a basic level usually involve:

  • Displaying data
  • Working with data
  • Navigation

The MVC design pattern helps you do those things, in a effect organized way. The direct translation would be:

  • Displaying data -> View : Think -> React, Angular, EJS
  • Working with data -> Model : Think -> Plain old classes (ORMs)
  • Navigation -> Controller : Think -> Express.js, Spring, Django

And there you have it, the MVC pattern explained. Now these direct translation might not be true for every framework out there, but for the most part they are true. You can this design pattern applied in almost every app frame work, form Metoer.js to ASP.Net MVC.

Note ORMs aren’t covered in this post, they require their own post to properly explain.

Hope that helped you guys understand.

OOP Explained

Preface

OOP is a way of thinking / design pattern. It can be understood by way of a number of different analogs. Not all the analogs described here are perfect but it makes some of the concepts easier to understand.

Blueprints:

Blueprints tell people how to make things, from your stove to your car. It has a clearly planned out way making sure everything works the way it is supposed to, and makes sure it satisfies it purpose.

You can think about “Classes” in the same way, expect what it builds is not something material, but an entity in computer. So if you wanted to make a car class you would thing about the things it should do. Such as accelerate, brake, turn on and off, open the door, and etc. Notice how all these things involve a verb , these actions that the car can take can be thought of as the methods in class. And then you have the stats of the care, such as the make, model, owner, and etc. These are all nouns and can be thought of as the variables of the classes.

There for when you instantiate a class, your telling the computer to build that objects using the guide (“Class”)

Collections of things:

People collect a lot of different things, from action figures, to stamps. These things all have common figures. Action figures are usually of a fictional character, are made of plastic, can be moved into different positions, and are usually a certain height .

And classes are the same, they hold variables and methods that come together since they are all kind of related. For example a coin classes could have a variable called “metal type” and a method called “flip”.

Cookie Cutters:

Cookie Cutters let you take cookie dough and make interestingly shaped cookies. Which is same thing as what a class does, except the cookie dough is your computers memory, and the cookie cutter is your class. Every time you instantiate a class,  your take some memory forcing it through the classes and making a object.