Build your 1st Python Web App with Flask.

Python is so powerful. The popularity and growth of Python is increasing day by day. Not only that, it’s easy to learn and use. What makes it unique is hundreds of open source python libraries and framework. In this post, we explore Flask, a micro and light weight web framework that you can use to save your time and effort by providing the required functionality.

We’ll start by installing the required libraries to start working with Flask and end by writing our all time favorite program “Hello World”. Let’s dive in.

Requirements and Setup.

1- Install virtualenv.

python3 -m pip install --user virtualenv

2-Create a virtual environment.

virtualenv env

3- Activate the environment.

source env/bin/activate

4- Install Flask

pip3 install Flask

Hello World 😊

Before doing any thing, it’s necessary to understand the Folder layout for Flask web app.

/env
  app.py (Your python file)
/env/static/styles
  main.css  
/env/static/img
  contains all the image
/env/templates
  index.html

Hello World! program in Flask is easy and ten lines long :) These ten lines of code are sufficient to create a simple web page.

So, let’s get started.
The code, once all written out, will look like this:

# app.py
from flask import Flask
app = Flask(__name__)

@app.route("/")
def fun():
  return 'Hello World!'
if __name__== '__main__':
    app.run()

Line 2- Import the required library.

from flask import Flask

Line 3- Create a new App.

app = Flask(__name__)

Line 5- Declare a “decorator”.

@app.route(“/”) # at the endpoint /

Lines 6,7- Define a function.

def fun():
  return 'Hello World!'

Lines 9,10- Run the application.

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

Running the Website

Once you have finished developing the code you can test it by running it using terminal(Oh, don’t tell me you hate Command Line/Terminal). You can run the command based on your file name.
For example, in my case it is app.py.

Till next time :) Happy Learning.

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Bilal Khan.