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Retrieving HTML From data using Flask

  • Difficulty Level : Easy
  • Last Updated : 16 Jul, 2020

Flask is a lightweight WSGI web application framework. It is designed to make getting started quick and easy, with the ability to scale up to complex applications. It began as a simple wrapper around Werkzeug and Jinja and has become one of the most popular Python web application frameworks.

Read this article to know more about Flask
Create form as HTML

We will create a simple HTML Form, very simple Login form




<form action="{{ url_for("gfg")}}" method="post">
<label for="firstname">First Name:</label>
<input type="text" id="firstname" name="fname" placeholder="firstname">
<label for="lastname">Last Name:</label>
<input type="text" id="lastname" name="lname" placeholder="lastname">
<button type="submit">Login</button>

Its an simple HTML form using the post method the only thing is unique is action URL. URL_for is an Flask way of creating dynamic URLs where the first arguments refers to the function of that specific route in flask. In our form it will create a Dynamic route which has gfg function in the flask app

Create Flask application



Start your virtual environment

pip install virtualenv
python3 -m venv env
pip install flask

Now we will create the flask backend which will get user input from HTML form




# importing Flask and other modules
from flask import Flask, request, render_template 
  
# Flask constructor
app = Flask(__name__)   
  
# A decorator used to tell the application
# which URL is associated function
@app.route('/', methods =["GET", "POST"])
def gfg():
    if request.method == "POST":
       # getting input with name = fname in HTML form
       first_name = request.form.get("fname")
       # getting input with name = lname in HTML form 
       last_name = request.form.get("lname"
       return "Your name is "+first_name + last_name
    return render_template("form.html")
  
if __name__=='__main__':
   app.run()

Working –

Almost everything is simple, We have created a simple Flask app, if we look into code

  • importing flask and creating a home route which has both get and post methods
  • defining a function with name gfg
  • if requesting method is post, which is the method we specified in the form we get the input data from HTML form
  • you can get HTML input from Form using name attribute and request.form.get() function by passing the name of that input as argument
    • request.form.get("fname") will get input from Input value which has name attribute as fname and stores in first_name variable
    • request.form.get("lname") will get input from Input value which has name attribute as lname and stores in last_name variable
  • The return value of POST method is by replacing the variables with their valuesYour name is "+first_name+last_name
  • the default return value for the function gfg id returning home.html template
  • you can review what-does-the-if-__name__-__main__-dofrom the article

Output –
Code in action
code
flask server running
flask server running
html form
html form
returning data from html template
retutning data

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