Back-end Web Framework: Flask (Part-3: How to make a simple Login Page using Get and Post)
For previous posts Part-1 and Part-2
HTTP protocol is the core basis of data communication in (WWW) world wide web. It is designed to communicate between clients and servers. It works as a request-respond protocol. HTTP has different methods of data retrieval from specified URL and those methods have been defined in this protocol.
GET: Browser requests server to get data in an unencrypted form stored on that page and send it. It’s the default method. It can be cached and remains in browser history.
HEAD: It is only interested in the headers and not the content of the page. It is supposed to be handled as if it was a GET request but not to deliver the actual content.
POST: It is used to send HTML form data to be processed to a specified resource. Browser tells the server that it wants to posts some new data to the URL and it is only stored once. Data received by POST method is not cached by server.
PUT: It replaces all current representations of the target resource with the uploaded content. Similar to Post, it might trigger the store procedure multiple times by overwriting the old data. It is helpful when suppose your connection is lost during transmission. In this situation a system between the browser and the server might receive the request safely a second time without breaking things.
DELETE: It removes all current representations of the target resource given by a URL.
CONNECT: It converts the request connection to a transparent TCP/IP tunnel
By default, a route answers to GET requests only, but that can be changed by providing the methods argument to the route() decorator. I am just going to use here two common HTTP methods: GET and POST
For GET request request.args.get('nm') is used .
For POST request request.form[‘nm’] is used.
To collect form data we require module: request
from flask import Flask, redirect, url_for, request
app = Flask(__name__)@app.route('/login',methods = ['POST', 'GET'])
def login():
if request.method == 'POST':
user = request.form['nm']
return redirect(url_for('success',name = user))
else:
user = request.args.get('nm')
return redirect(url_for('success',name = user))@app.route('/success/<name>')
def success(name):
return 'welcome %s' % nameif __name__ == '__main__':
app.run(debug = True)
The HTML code is
<html>
<body>
<form action = "http://localhost:5000/login" method="post">
<p> Enter Name:</p>
<p> <input type="text" name="nm"></p>
<p> <input type="submit" name="submit"></p>
</form>
</body>
</html>The http://localhost:5000/login is mapped to login() function. As the server has received the submitted data by POST method, value of ‘nm’ parameter obtained from the form data is by: user = request.form[‘nm’] . It is then passed to the /success URL as the variable part /<name> . The browser will display it on the screen.
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