CODEWITHSUNDEEP
flask
SantoshGupta7
SantoshGupta7

Reputation: 6197

404 when using `redirect` and `url_for` in flask

I am trying to test out redirects in flask. I can go directly to an endpoint url no problem, but when I try to redirect to it, I get an error message.

Edit: I changed the name of the method, call, and url to 'predict' but still getting the same error.

This is what my code looks like

from flask import Flask, request, render_template, jsonify
from flask_ngrok import run_with_ngrok
from flask import redirect, url_for

app = Flask(__name__)
run_with_ngrok(app)

@app.route('/QueryParser', methods=['GET', 'POST'])
def query():

    if request.method == 'GET':
        return render_template('index.html', value='hi')
    else:
        body = request.get_json()

        question_textN = body['question']
        context_textN = body['context']

        return redirect(url_for('predict', question=question_textN, 
                        context=context_textN))

@app.route("/predict/<question>/<context>", methods=["GET"])
def predict(question, context):

    question_text = question
    context_text = context

    return jsonify(answer=question_text, context=context_text)

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

At this particular instance, its running on

http://688adffe.ngrok.io/QueryParser

When I put in a context and query and hit ask, nothing happens, and I see this in my commandline output

 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
 * Running on http://688adffe.ngrok.io
 * Traffic stats available on http://127.0.0.1:4040
127.0.0.1 - - [21/Feb/2020 03:51:48] "GET / HTTP/1.1" 404 -
127.0.0.1 - - [21/Feb/2020 03:51:48] "GET /favicon.ico HTTP/1.1" 404 -
127.0.0.1 - - [21/Feb/2020 03:51:55] "GET /QueryParser HTTP/1.1" 200 -
127.0.0.1 - - [21/Feb/2020 03:52:01] "POST / HTTP/1.1" 404 -

It works just fine if I go directly to the url

http://688adffe.ngrok.io/predict/test1/test2

I get this in the command line output

127.0.0.1 - - [21/Feb/2020 02:07:28] "GET /ModelInference/test1/test2 HTTP/1.1" 200 -

And there is an output (though I was aiming to have the output passed to the html but I can worry about that later)

{
  "answer": "test1", 
  "context": "test2"
}

To recreate the minimal example, use this code which downloads files from my google drive. Note that flask versions above 1.0 sometimes do not work with flask_ngrok. In some cases, only version 0.12.5 or 0.12.4 works. 

!pip install flask==1.0
!pip install flask-ngrok
import os
if not os.path.exists('templates'):
    os.mkdir('templates')

%cd templates
!gdown --id 1-l3SlwyyNjSV-bzUnyw1ZpPaPQz3KUYP
%cd ..
!gdown --id 1s_lGCf_T0619RWZKBjQ_oES0jwmNSn2F

!python rest-testMin.py

For convenience, here's a google colab link that has this code ready to execute

https://colab.research.google.com/drive/1uxbR0-c75njIq5dckSpKVaklZkrTb4kf

Upvotes: 0

Views: 962

Answers (1)

Bitto
Bitto

Reputation: 8245

The first argument to url_for should be the name of the view function. It should be 

return redirect(url_for('predict', question=question_textN, context=context_textN))

From the Docs

flask.url_for(endpoint, **values)

Generates a URL to the given endpoint with the method provided.

Also,

From your server output

127.0.0.1 - - [21/Feb/2020 03:52:01] "POST / HTTP/1.1" 404 -

It seems that you have not set the form action attribute correctly to point to the query view function.

<form method="post" action="{{url_for('query')}}">
...
</form>

Upvotes: 1

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