So this is going to be very fun and also, hopefully, it's going to give you a good idea on the architecture that you're going to use whenever you're building out API clients, and if you are coming at this from a front-end perspective.

So if you spend quite a bit of your time building out applications such as React apps, or Angular, or Vue applications, then typically you're going to be working with some type of backend API and so throughout these few sections we're going to build out multiple projects and you're going to see exactly how the back end side of that works.

Now, this very first project is going to be very basic and the whole goal of this is to give you a base case scenario and get you familiar with some of the commands and the basic flow of building out an API application.

One thing I will say is that if you are a fan of the Python programming language I think you're really going to like working with Flask because Flask is very close to writing pure Python, it simply gives you some additional tools layered on top of Python so that you can have APIs.

So that's where we're going to walk through in this first section. And in this guide specifically, we're just going to see how we can build out our basic environment. So this is going to be pretty common across all of the projects. This is a good reference point for you.

Now a couple of requirements that I want you to have before going through this is make sure that you have pipenv installed on in your environment. So the Pip environment tool that we walked through before and then make sure that you also have the Postman client.

Postman is going to allow us to test out our APIs. And then lastly make sure that you have some type of text editor. Now I personally am going to be using VIM throughout all of these guides but you can use Visual Studio code you can use Sublime Text, or Atom. It's completely up to you. That will not change how everything works.

So let's get started. The very first thing that I do is I'm going to create a directory for our project so I'm going to call it hello-flask and then I'm going to change into it. Now I want to create a development environment inside of it so I'm going to say pipenv --three so this is going to create a pip file and it's going to allow us to start adding our own dependencies.

We're going to start off just by adding Flask, so now by type ls you can see that we have a pip file there and if you're working with a text editor such as visual studio code or sublime text right now would be a good time to open up that project.

Now, I'm going to go through it using VIM throughout the rest of the course. So now that we have that let's install Flask. So I'm going to say pipenv install flask and this is going to go into our Pip file it's going to add Flask as a dependency and then it's going to go up to the PI shop and it's going to go and bring it down into our system.

We can test this out by now looking at the pip file and you can see now around line 14 you should now have Flask

You can also see that we're working with Python 3.6. That's the basic setup that you're going to want to use. And now we're going to create an app file so if you're following along in some other text editor simply right click on the left-hand side and create a file called app.py and now let's add just a few lines of code.

app.py

from flask import flask

app = Flask(__name__)

Now we're going to create our first route so a route, as you may be familiar with, is simply an endpoint that we can go into our application with, and the way that routes are created in Flask is they use a tool that is called a decorator and so a decorator in computer science terms is code that you can wrap around methods or classes.

So in this case, the way that Python uses decorators is it starts with an @ symbol and so let's build this out.

app.py

from flask import Flask

app = Flask(__name__)

@app.route('/')
def hello():
    return "Hey Flask"

if __name__ == '__main__':
    app.run(debug=True)

And that is it. Let's save this file and then we're going to walk through it in a second after we confirm that it is all working. So let's start up a shell session. pipenv shell So this is going to get Python going with the version of 3.6 that we need it to be.

And now to test out our application, simply run python app.py. So notice that this is exactly the same process is if you had built out a basic terminal type of program in Python. And as long as you don't get any error messages, it means everything should be working.

And now we can test this out. So if you notice if you look at this debug log it says that it's running on this URL. Now, this URL http://127.0.0.1:5000/ This is the same as saying localhost so I can say localhost:5000 and that is going to take us where we want to be.

So I can go to a localhost:5000 and you can see that it says 'Hey Flask'.

So if you have gone through all of that and you're seeing 'Hey Flask' that means that you have built your first Flask API application. So great job if you did that we still are going to be adding quite a bit too, so don't worry it's going to get much more complex even for our basic example but just know if you are at this point right now that means everything's working you haven't run into any errors and you have a basic Flask setup.

So this is the server and so the server's running. In order to end it you can see that you have the code to end it, so if you press CTRL+C that will end the server session.

That ended it and if I go back to the browser now and I try to run localhost 5000 now we simply get an error which is what we'd expect because a server is no longer running.

So great job if you went through that you now have built out your very first Flask application and as we go through this particular project we're going to start building out a full-scale type of JSON based API.

Source Code

• Code at this stage

https://docs.pipenv.org/ Guide on installing pipenv