Flask is a web application framework written in Python. Flask is easy to get started with as a beginner because there is little boilerplate code for getting a simple app up and running.
If you do not have Python installed on your computer, download the
installer from the Python official website.
To make sure your Python installation is functional, you can open a
terminal window and type python3, or if that does not work, just python.
python3
which returns
Python 3.8.10 (default, Nov 26 2021, 20:14:08)
[GCC 9.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
To exit the interactive prompt, you can type exit() and press Enter. On
the Linux and Mac OS X versions of Python you can also exit the
interpreter by pressing Ctrl+D. On Windows, the exit shortcut is Ctrl+Z,
followed by Enter.
In Python, packages such as Flask are available in a public repository,
from where anybody can download and install them. The official
Python package repository is called PyPI, which stands for Python
Package Index.
Optionally, if you have not installed pip, run the following command:
apt install python3-pip
Install Flask.
pip install Flask
Create a folder called FlaskApp.
mkdir FlaskApp
Navigate to the FlaskApp folder and create a file called app.py.
cd FlaskApp
nano app.py
Paste the following content to the app.py file.
from flask import Flask
app = Flask(__name__)
@app.route("/")
def main():
return "Welcome to the first Flask App!"
if __name__ == "__main__":
app.run(host='0.0.0.0')
Save the changes and execute app.py.
python3 app.py
which returns
* Serving Flask app "app" (lazy loading)
* Environment: production
WARNING: Do not use the development server in a production
environment.
Use a production WSGI server instead.
* Debug mode: off
* Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)
Open you web browser and type the server_ip:port. It should display:
Note
If you run the server you will notice that the server is only accessible from your own computer, not from any other in the network. This is the default because in debugging mode a user of the application can execute arbitrary Python code on your computer. If you have the debugger disabled or trust the users on your network, you can make the server publicly available simply by adding —host=0.0.0.0 to the command line or editting your app.py to match `app.run(host=‘0.0.0.0’)“ This tells your operating system to listen on all public IPs.
In Flask, templates are written as separate files, stored in a templates folder that is inside the application package. So after making sure that you are in the FlaskApp directory, create the directory where templates will be stored.
Following the procedure to create applications shown in the previous steps, we will create a new application called hello.py running on port 80. with the following configuration:
from flask import Flask, flash, redirect, render_template, request,
session, abort
app = Flask(__name__)
@app.route("/")
def index():
return "Flask App!"
@app.route("/hello/<string:name>/")
def hello(name):
return render_template(
'test.html',name=name)
if __name__ == "__main__":
app.run(host='0.0.0.0', port=80)
Create a directory called templates:
mkdir templates
Create a test.html file:
nano test.html
Paste the following code into your test.html file, save your changes, and exit.
{% extends "layout.html" %} {% block body %}
<divclass="block1">
<h1>Hello {{name}}!</h1>
<h2>Discover a New Cloud Experience</h2>
<p>
"The Disruptive Cloud Computing Platform: Deploy SSD Cloud Servers in
seconds!!"
</p>
</div>
{% endblock %}
Create a layout.html file using nano layout.html, and paste the following code:
Let’s try and display random Scaleway catch phrase instead of always the same one. We will need to pass both the name and the quote variables.
In the templates directory, edit test.html to match the following:
{% extends "layout.html" %} {% block body %}
<divclass="block1">
<h1>Hello {{name}}!</h1>
<h2>Discover a New Cloud Experience</h2>
<p>{{quote}}</p>
</div>
{% endblock %}
Save and exit.
In the application called hello.py, update the configuration to look like the following:
from flask import Flask, flash, redirect, render_template, request, session, abort
from random import randint
app = Flask(__name__)
@app.route("/")
def index():
return "Flask App!"
#@app.route("/hello/<string:name>")
@app.route("/hello/<string:name>/")
def hello(name):
# return name
quotes = [ "Pay as You Go - Enjoy a new cloud experience starting at 0.004euros per hour.",
"Multiple Datacenters - Maximize your services reliability by running your infrastructure through autonomous facilities spread across multiple regions.",
"Over 5 Tb/s of internet bandwidth - Deliver your content anywhere thanks to our multiple high-end transit providers and the best peerings.",
"Limitless Infrastructure Combinations - Additional volumes, movable IPs, security groups and hot snapshots are available on all our servers.",
"Developer Tools - Interact with Scaleway and take control of the cloud in minutes with our many tools, resources and third-party applications.",
"Hourly Billing - All our cloud resources are billed per hour with monthly capping. Scaleway pricing is predictable and transparent, with no hidden costs."$
randomNumber = randint(0,len(quotes)-1)
quote = quotes[randomNumber]
return render_template(
'test.html',**locals())
if __name__ == "__main__":
app.run(host='0.0.0.0', port=80)
As you can notice, we updated the quotes variable with an array of multiples quotes. These can be accessed as quote[0], quote[1], quote[2] and so on. The function randint() returns a random number between 0 and the total number of quotes, one is subtracted because we start counting from zero.
We also added a locals() function which always returns a dictionary of the current namespace.