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Getting Started With Python Flask

Installing Flask using pip tool

We can install Flask using Python pip tool. As we are using Python3, the below command will install Flask framework on to your machine.

$ pip3 install flask

The above command will install Flask and its dependencies.

Writing our first Flask application

We will write a simple Flask application with two routes, index route (“/”) and something line “/<user>” route. Route is nothing but the URL structure. Before that we will create the structure of our application:

  1. Create a folder called flask-app.
  2. Create a file called simple_flask.py inside flask-app folder.

Copy the below code to simple_flask.py file:

Execute the application locally using

$ python3 simple_flask.py

Flask comes with inbuilt development server which runs on http://127.0.0.1:5000. Open the link in the browser and you will see the message “Welcome to Flask”. If you change the route to http://127.0.0.1:5000/saisyam you will see the message “Hi saisyam!”.

When the base URL is called, I mean, http://127.0.0.1:5000, Flask will check for the appropriate root, in our example, it is:

@app.route('/')
def index():
    return "Welcome to Flask"

The base route is “/” and hence Flask will show the message under this route. Similarly for the second route, http://127.0.0.1/saisyam the below code is executed:

@app.route('/<user>')
def hi_user(user):
    return "Hi "+user+"!"

Here <user> is a variable which is substituted with a string, in our case it is, “saisyam”.

So, we have successfully created our first Flask web application. Hope you got the basic idea of how routes work in a web application.


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