How do i host a python flask web application?
by Salvador Villalon Show
IntroductionIn each section, I will show pieces of code for you to follow along. All the code used in the tutorial is available in this GitHub Repository. What is HTTP and What Does it Have to do with Flask?HTTP is the protocol for websites. The internet uses it to interact and communicate with computers and servers. Let me give you an example of how you use it everyday. When you type the name of a website in the address bar of your browser and you hit enter. What happens is that an HTTP request has been sent to a server. For example, when I go to my address bar and type google.com, then hit enter, an HTTP request is sent to a Google Server. The Google Server receives the request and needs to figure how to interpret that request. The Google Server sends back an HTTP response that contains the information that my web browser receives. Then it displays what you asked for on a page in the browser. How is Flask involved?We will write code that will take care of the server side processing. Our code will receive requests. It will figure out what those requests are dealing with and what they are asking. It will also figure out what response to send to the user. To do all this we will use Flask. What is Flask?Flask (A Python Microframework)It makes the process of designing a web application simpler. Flask lets us focuson what the users are requesting and what sort of response to give back. Learn more about micro frameworks. How Does a Flask App Work?The code lets us run a basic web application that we can serve, as if it were a website.
This piece of code is stored in our main.py. Line 1: Here we are importing the Flask module and creating a Flask web server from the Flask module. Line 3: __name__ means this current file. In this case, it will be main.py. This current file will represent my web application. We are creating an instance of the Flask class and calling it app. Here we are creating a new web application. Line 5: It represents the default page. For example, if I go to a website such as “google.com/” with nothing after the slash. Then this will be the default page of Google. This is what the @app.route(“/”) will representLine 6–7: When the user goes to my website and they go to the default page (nothing after the slash), then the function below will get activated. Line 9: When you run your Python script, Python assigns the name “__main__” to the script when executed. If we import another script, the if statement will prevent other scripts from running. When we run main.py, it will change its name to __main__ and only then will that if statement activate. Line 10: This will run
the application. Having Let’s Try Running main.pyIn your Terminal or Command Prompt go to the folder that contains your main.py.Then do The important part is where it says 127.0.0.1 means this local computer. If you do not know the meaning of this (like I didn’t when I started — this article is really helpful), the main idea is that 127.0.0.1 and localhost refer to this local computer. Go to that address and you should see the following: Congrats! You made a website with Flask!More Fun with FlaskEarlier you saw what happened when we ran main.py with one route which was app.route(“/”). Let’s add more routes so you can see the difference.
In lines 9–11. we added a new route, this time to /salvador. Now run the main.py again and go tohttp://localhost:5000/salvador. So far we have been returning text. Let’s make our website look nicer by adding HTML and CSS. HTML, CSS, and Virtual EnvironmentsHTML and Templates in FlaskFirst create a new HTML file. I called mine home.html. Here is some code to get you started.
Important Point To RememberThe Flask Framework looks for HTML files in a folder called templates. You need to create a templates folder and put all your HTML files in there. Remember to always keep the main.py outside of your templates folderNow we need to change our main.py so that we can view the HTML file we created.
Line 1: We imported Line 7: We change the return so that now it returns Now visit your localhost and see the changes: http://localhost:5000/. Let’s add more pagesLet’s create an about.html inside the templates folder.
Let’s make a change similar to what we did before to our main.py.
We made three new changes: Line 9:
Change the route to Line 10: Change the function so it is now Line 11: Change the return so that now it returns Now see the changes: http://localhost:5000/about. Let’s Connect Both Pages with a NavigationTo connect both pages we can have a navigation menu on the top. We can use Flask to make the process of creating a navigation menu easier. First, let’s create a template.html. This template.html will serve as a parent template. Our two child templates will inherit code from it.
Line 13–14: We use the function called The two lines with the curly brackets will be replaced by the content of home.html and about.html. This willdepend on the URL in which the user is browsing. These changes allow the child pages (home.html and about.html) to connect to the parent (template.html). This allows us to not have to copy the code for the navigation menu in the about.html and home.html. Content of about.html:
Content of home.html:
Let’s try adding some CSS. Adding CSS to Our WebsiteAn important note to rememberIn the same way as we created a folder called templates to store all our HTML templates, we need a folder called static. In static, we will store our CSS, JavaScript, images, and other necessary files. That is why it is important that you should create a CSS folder to store your stylesheets. After you do this, your project folder should look like this: Linking our CSS with our HTML fileOur template.html is the one that links all pages. We can insert the code here and it will be applicable to all child pages.
Line 7: Here we are giving the path to where the template.css is located. Now see the changes: http://localhost:5000/about. Moving Forward with Flask and virtualenvNow that you are familiar with using Flask, you may start using it in your future projects. One thing to always do is use virtualenv. Why use virtualenv?You may use Python for others projects besides web-development. Your projects might have different versions of Python installed, different dependencies and packages. We use virtualenv to create an isolated environment for your Python project. This means that each project can have its own dependencies regardless of what dependencies every other project has. Getting started with virtualenvFirst, run this command on your command prompt or terminal:
Second, do the following:
Here you can give a name to the environment. I usually give it a name of virtual. It will look like this: After setting up virtual environment, check your project folder. It should look like this. The virtual environment needs to be created in the same directory where your app files are located. How the directory looks likeActivating the virtual environmentNow go to your terminal or command prompt. Go to the directory that contains the file called activate. The file called activate is found inside a folder called Scripts for Windows and bin for OS X and Linux. For OS X and Linux Environment:
For Windows Environment:
Since I am using a Windows machine, when I activate the environment it will look like this: You should see this at beginning of your command prompt lineThe next step is to install flask on your virtual environment so that we can run the application inside our environment. Run the command:
Run your application and go to http://localhost:5000/ We finally made our web application. Now we want to show the whole world our project. (More information on virtualenv can be found in the following guides on virtualenv and Flask Official Documentation) Let’s send it to the CloudTo show others the project we made, we will need to learn how to use Cloud Services. Deploy Your Web Application to the CloudTo deploy our web application to the cloud, we will use Google App Engine (Standard Environment). This is an example of a Platform as a Service (PaaS). PaaS refers to the delivery of operating systems and associated services over the internet without downloads or installation. The approach lets customers create and deploy applications without having to invest in the underlying infrastructure (More info on PaaS check out TechTarget). Google App Engine is a platform as a service offering that allows developers and businesses to build and run applications using Google’s advanced infrastructure — TechOpedia. Before you Start:You will need a Google Account. Once you create an account, go to the Google Cloud Platform Console and create a new project. Also, you need to install the Google Cloud SDK. At the end of this tutorial your project structure will look like this. Project Folder StructureWe will need to create three new files: app.yaml, appengine_config.py, and requirements.txt. Content of app.yaml:
If you were to check Google’s Tutorial in the part where they talk about content of the app.yaml, it does not include the section where I wrote about libraries. When I first attempted to deploy my simple web app, my deployment never worked. After many attempts, I learned that we needed to include the SSL library. The SSL Library allows us to create secure connections between the client and server. Every time the user goes to our website they will need to connect to a server run by Google App Engine. We need to create a secure connection for this. (I recently learned this, so if you have a suggestions for this let me know!) Content of appengine_config.py:
Content of requirements.txt:
Now inside our virtual environment (make sure your virtualenv is activated),we are going to install the new dependencies we have in requirements.txt. Run this command:
-t lib: This flag copies the libraries into a lib folder, which uploads to App Engine during deployment. -r requirements.txt: Tells pip to install everything from requirements.txt. Deploying the ApplicationTo deploy the application to Google App Engine, use this command.
I usually include — project [ID of Project] This specifies what project you are deploying. The command will look like this:
The ApplicationNow check the URL of your application. The application will be store in the following way:
My application is here: http://sal-flask-tutorial.appspot.com ConclusionFrom this tutorial, you all learned how to:
What I learnedI learned three important things from this small project. First, I learned about the difference between a static website and a web application Static Websites:
Web Applications:
Server Side and Client Side:
Second, I learned about Cloud Services Most of my previous projects were static websites, and to deploy them I used GitHub Pages. GitHub Pages is a free static site hosting service designed to host projects from a GitHub Repository. When working with web applications, I could not use GitHub Pages to host them. GitHub Pages is only meant for static websites not for something dynamic like a web application that requires a server and a database. I had to use Cloud Services such as Amazon Web Services or Heroku Third, I learned how to use Python as a Server Side Language To create the server side of the web application we had to use a server side language. I learned that I could use the framework called Flask to use Python as the Server Side Language. Next Steps:You can build all sorts of things with Flask. I realized that Flask helps make the code behind the website easier to read. I have made the following applications during this summer of 2018 and I hope to make more. Personal Projects
During my internship
Here is the list of resources that helped me create this tutorial:
If you have any suggestions or questions, feel free to leave a comment. Learn to code for free. freeCodeCamp's open source curriculum has helped more than 40,000 people get jobs as developers. Get started How do I host a Flask Web App?Step 1: Creating a Python Virtual Environment for your Project. Before you get started, you need to set up your Python developer environment. ... . Step 2: Creating a Minimal Flask App. ... . Step 3: Setting Up Your Gunicorn Configuration. ... . Step 4: Pushing the Site to GitHub. ... . Step 5: Deploying to DigitalOcean with App Platform.. Where can I host a Flask website?Easiest and fastest way to host Flask Python. PythonAnywhere.com (web-SSH; web-instant-MySQL-db; web-IDE; instant deployment of flask, free; easy logs; github/single-file-upload support; SFTP/SSH requires pay). Nitrious.io (web-IDE; SSH; free; requires "websocket"-supporting browser; upgradeable cloud service). How do you deploy a Python Flask Web app for free?How can I deploy my flask web app on vercel?. Download vercel cli using npm i -g vercel . Refer here.. add requirements. txt file with all the python packages mentioned you've used.. add vercel.json file and add the below content(here I am using app.py as my main file). How do I host a Flask API in Python?So, let's hit it!. Create a repo on GitHub. First things first, we need our working code to be available on GitHub, because that's how we are linking it to Heroku. ... . Create a venv. ... . Activate the venv. ... . Install flask and gunicorn. ... . Create the . ... . Create the api.py file. ... . Create a requirements. ... . Create a Procfile.. |