Modern web apps use a technique named routing. This helps the user remember the URLs. For instance, instead of having /booking.php they see /booking/. Instead of /account.asp?id=1234/ they’d see /account/1234/.

Related course: Python Flask: Create Web Apps with Flask

Routes

flask route example

Routes in Flask are mapped to Python functions. You have already created one route, the ‘/‘ route:

@app.route('/')
    def index():

The route() decorator, @app.route(), binds a URL to a function.

If you want the route /hello, you can bind it to the hello_world() function like this:

@app.route('/hello')
def hello_world():
   return "hello world"

The output of the function hello_world() is shown in your browser.

flask route params

Parameters can be used when creating routes. A parameter can be a string (text) like this: /product/cookie.

That would have this route and function:

@app.route('/product/<name>')
def get_product(name):
  return "The product is " + str(name)

So you can pass parameters to your Flask route, can you pass numbers?

The example here creates the route /sale/<transaction_id>, where transaction_id is a number.

@app.route('/sale/<transaction_id>')
def get_sale(transaction_id=0):
  return "The transaction is "+str(transaction_id)

flask route multiple arguments

If you want a flask route with multiple parameters that’s possible. For the route /create/<first_name>/<last_name> you can do this:

@app.route('/create/<first_name>/<last_name>')
def create(first_name=None, last_name=None):
  return 'Hello ' + first_name + ',' + last_name

flask route post

Flask suports HTTP POST requests. If you are unfamiliar with this, I recommend this course: Create apps with Flask.

Create a template named login.html

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<html>
   <body>
      <form action = "http://localhost:5000/login" method = "post">
         <p>Username:</p>
         <p><input type = "text" name = "name" /></p>
         <p><input type = "submit" value = "submit" /></p>
      </form>
   </body>
</html>

The code below supports both type of HTTP requests.

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from flask import Flask
from flask import render_template
from flask import request

from flask import Flask, redirect, url_for, request
app = Flask(__name__)

@app.route('/dashboard/<name>')
def dashboard(name):
   return 'welcome %s' % name

@app.route('/login',methods = ['POST', 'GET'])
def login():
   if request.method == 'POST':
      user = request.form['name']
      return redirect(url_for('dashboard',name = user))
   else:
      user = request.args.get('name')
      return render_template('login.html')

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

If you get an error like this, your routing is wrong:

werkzeug.routing.BuildError
werkzeug.routing.BuildError: Could not build url for endpoint 'dashboard'. Did you forget to specify values ['name']?

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