We'll discuss redirects and errors with PythonFlask in this article. A redirect is used in the Flask class to send the user to a particular URL with the status code. conversely, this status code additionally identifies the issue. When we access a website, our browser sends a request to the server, and the server replies with what is known as the HTTP status code, which is a three-digit number, The different reasons for errors are:
- Unauthorized access or poor request.
- Unsupported media file types.
- Overload of the backend server.
- Internal hardware/connection error.
Syntaxof Redirect
flask.redirect(location,code=302)
Parameters:
- location(str):the location which URL directs to.
- code(int): The status code for Redirect.
- Code: The default code is 302 which means that the move is only temporary.
Return:The response object and redirects the user to another target location with the specified code.
The different types of HTTP codes are:
| Code | Status |
|---|
| 300 | Multiple_choices |
| 301 | Moved_permanently |
| 302 | Found |
| 303 | See_other |
| 304 | Not_modified |
| 305 | Use_proxy |
| 306 | Reserved |
| 307 | Temporary_redirect |
Import the redirect attribute
We can redirect the URL using Flask by importingredirect.Let's see how to import redirects from Flask
Python3Example:
Let's take a simple example to redirect the URL using a flask namedapp.py.
Python3# importing redirectfromflaskimportFlask,redirect,url_for,render_template,request# Initialize the flask applicationapp=Flask(__name__)# It will load the form template which# is in login.html@app.route('/')defindex():returnrender_template("login.html")@app.route('/success')defsuccess():return"logged in successfully"# loggnig to the form with method POST or GET@app.route("/login",methods=["POST","GET"])deflogin():# if the method is POST and Username is admin then# it will redirects to success url.ifrequest.method=="POST"andrequest.form["username"]=="admin":returnredirect(url_for("success"))# if the method is GET or username is not admin,# then it redirects to index method.returnredirect(url_for('index'))if__name__=='__main__':app.run(debug=True)login.html
Create a folder named templates. In the templates, creates a templates/login.html file. On this page, we will take input from the user of its username.
HTML<!DOCTYPE html><htmllang="en"><body><formmethod="POST",action="\login"> Username:<inputname=usernametype=text></input><br><buttontype="submit">Login</button></form></body></html>
Now we will deploy our code.
python app.py
Output:
Case 1: If the Username isadminand the method isPOSTthen it will redirect to the success URL and display logged in successfully.
Case 2: In the other case, if the Username is something like xyz or anything then it will redirect to theindexmethod i.e., it will load the form again until the username is admin.
Flasks Errors
If there is an error in the address or if there is no such URL then Flask has anabort() function used to exit with an error code.
Syntax of abort() method
Syntax:abort(code, message)
- code: int, The code parameter takes any of the following values
- message: str, create your custom message Error.
The different types of errors we can abort in the application in your Flask.
| Code | Error |
|---|
| 400 | Bad request |
| 401 | Unauthenticated |
| 403 | Forbidden |
| 404 | Not Found |
| 406 | Not Acceptable |
| 415 | Unsupported Media Type |
| 429 | Too Many Requests |
Example to demonstrate abort
In this example, if the username starts with a number then an error code message will through, else on success "Good username" will be printed.
Example 1:
Python3# importing abortfromflaskimportFlask,abort# Initialize the flask applicationapp=Flask(__name__)@app.route('/<uname>')defindex(uname):ifuname[0].isdigit():abort(400)return'<h1>Good Username</h1>'if__name__=='__main__':app.run()Output:
Case 1: If the username doesn't start with a number.
Case 2: If the username starts with a number.
Example 2:
In the above Python code, the status code to the abort() is400, so it raises a Bad Request Error. Let's try to change the code to403. If the username starts with a number then it raises a Forbidden Error.
Python3# importing abortfromflaskimportFlask,abort# Initialize the flask applicationapp=Flask(__name__)@app.route('/<uname>')defindex(uname):ifuname[0].isdigit():abort(403)return'<h1>Good Username</h1>'if__name__=='__main__':app.run()Output:
