How to accept empty url route in flask?

Question

I am working with hardware machines whose firmware cannot be changed. I am supposed to make a server from them the only thing I can configure is IP and port.

For starters, I made the following server in Flask

from flask import Flask

app = Flask(__name__)


@app.route("/" ,methods=['GET', 'POST', 'DELETE', 'PATCH'])
def hello_world():
    return 'Hello World!'


if __name__ == '__main__':
    app.run(host='0.0.0.0',port=5000)

I was getting a 308 error:

error 308

Then I used the following catch-all url approach to help my case.

from flask import Flask

app = Flask(__name__)


@app.route("/", defaults={"path": ""},methods=['GET', 'POST', 'DELETE', 'PATCH'])
@app.route("/<string:path>",methods=['GET', 'POST', 'DELETE', 'PATCH'])
@app.route("/<path:path>",methods=['GET', 'POST', 'DELETE', 'PATCH'])
def hello_world():
    return 'Hello World!'


if __name__ == '__main__':
    app.run(host='0.0.0.0',port=5000)

But still, I am getting the same error:

the error

Tried it , I got 405 which meant method not allowed, I then added methods parameter and it was back to 308. — Christopher V. Young
– Christopher V. Young, Commented May 11, 2019 at 10:01
If you look at the second screenshot the request it not even coming at '/' it is coming at empty. normally there is a / if you send a request to that route — Christopher V. Young
– Christopher V. Young, Commented May 11, 2019 at 10:03
Does this answer your question? Why does my Flask app return a response with status code 308 under test? — NicoNing
– NicoNing, Commented Apr 28, 2021 at 11:38

Michael Spagon · Accepted Answer · 2019-05-11 08:45:06Z

4

Since I don't have 50 reputation yet, I can't comment so I'll leave this here.

You want to use the path variable for routes:

"A simple way to create a Catch-All function which serves every URL including / is to chain two route filters. One for the root path '/' and one including a path placeholder for the rest.

We can't just use one route filter including a path placeholder because each placeholder must at least catch one character."

from flask import Flask
app = Flask(__name__)

@app.route('/', defaults={'path': ''})
@app.route('/<path:path>')
def catch_all(path):
    return 'You want path: %s' % path

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

% curl 127.0.0.1:5000          # Matches the first rule
You want path:  
% curl 127.0.0.1:5000/foo/bar  # Matches the second rule
You want path: foo/bar

http://flask.pocoo.org/snippets/57/

answered May 11, 2019 at 8:45

Michael Spagon

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1 Comment

Christopher V. Young Over a year ago

Tried it , I got 405 which meant method not allowed, I then added methods parameter and it was back to 308.

NicoNing · Accepted Answer · 2021-04-28 11:46:33Z

2

If you insist to use empty route, Just set app.route with strict_slashes=False, like this:

from flask import reqeust
@app.route('/', methods = ['GET','POST','DELETE', 'PATCH'], 
           strict_slashes=False)
def hello():
    return f"hello, {request.method}"

Because Flask use werkzeug.routing.Rule, which enable strict_slashes as default, visiting a branch URL without a trailing slash will redirect to the URL with a slash appended. Which cause response with 308 (Permanent Redirect).

refer: https://werkzeug.palletsprojects.com/en/1.0.x/routing/

answered Apr 28, 2021 at 11:46

NicoNing

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1 Comment

Michael-O Over a year ago

Still applies to 2.2.x

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