Flask class has a redirect() function. When called, it returns a response object and redirects the user to another target location with specified status code.

Prototype of redirect() function is as below −

Flask.redirect(location, statuscode, response)

In the above function −

• location parameter is the URL where response should be redirected.

• statuscode sent to browser’s header, defaults to 302.

• response parameter is used to instantiate response.

The following status codes are standardized −

• HTTP_300_MULTIPLE_CHOICES
• HTTP_301_MOVED_PERMANENTLY
• HTTP_302_FOUND
• HTTP_303_SEE_OTHER
• HTTP_304_NOT_MODIFIED
• HTTP_305_USE_PROXY
• HTTP_306_RESERVED
• HTTP_307_TEMPORARY_REDIRECT

The default status code is 302, which is for ‘found’.

In the following example, the redirect() function is used to display the login page again when a login attempt fails.

from flask import Flask, redirect, url_for, render_template, request
# Initialize the Flask application
app = Flask(__name__)

@app.route(''/'')
def index():
   return render_template(''log_in.html'')

@app.route(''/login'',methods = [''POST'', ''GET'']) 
def login(): 
   if request.method == ''POST'' and request.form[''username''] == ''admin'' :
      return redirect(url_for(''success''))
   else:
      return redirect(url_for(''index''))

@app.route(''/success'')
def success():
   return ''logged in successfully''
	
if __name__ == ''__main__'':
   app.run(debug = True)

Flask class has abort() function with an error code.

Flask.abort(code)

The Code parameter takes one of following values −

• 400 − for Bad Request

• 401 − for Unauthenticated

• 403 − for Forbidden

• 404 − for Not Found

• 406 − for Not Acceptable

• 415 − for Unsupported Media Type

• 429 − Too Many Requests

Let us make a slight change in the login() function in the above code. Instead of re-displaying the login page, if ‘Unauthourized’ page is to be displayed, replace it with call to abort(401).

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

@app.route(''/'')
def index():
   return render_template(''log_in.html'')

@app.route(''/login'',methods = [''POST'', ''GET''])
def login():
   if request.method == ''POST'':
      if request.form[''username''] == ''admin'' :
         return redirect(url_for(''success''))
      else:
         abort(401)
   else:
      return redirect(url_for(''index''))

@app.route(''/success'')
def success():
   return ''logged in successfully''

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