TypeError: The view function did not return a valid response.The function either returned None or ended without a return statement how to solve in Flask?

K

kriventseff2021-02-20 15:44:28

Flask

kriventseff, 2021-02-20 15:44:28

python code

from flask import Flask, render_template, url_for, request, redirect
from flask_sqlalchemy import SQLAlchemy
from datetime import datetime

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///poem.db'
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
db = SQLAlchemy(app)

class Ivan(db.Model):
    id = db.Column(db.Integer, primary_key = True)
    author = db.Column(db.String(100), nullable = False)
    namepoem = db.Column(db.String(200), nullable = False)
    poem = db.Column(db.Text, nullable = False)
    date = db.Column(db.DateTime, default = datetime.utcnow)

    def __repr__(self):
        return '<Ivan %r>' % self.id

@app.route('/')
def index():
    return 'Hello World!'

@app.route('/create-poem/', methods=['POST', 'GET'])
def create():
    if request.method == 'POST':
        author = request.form['author']
        name = request.form['namepoem']
        poem = request.form['poem']
        ivan = Ivan(author=author, namepoem=name, poem=poem)
        try:   
            db.session.add(ivan)
            db.session.commit()
            return redirect('/')
        except:
            pass
    else:
        return render_template('create.html')




app.run(debug=True)

html code

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" integrity="sha384-ggOyR0iXCbMQv3Xipma34MD+dH/1fQ784/j6cY/iJTQUOhcWr7x9JvoRxT2MZw1T" crossorigin="anonymous">

    <title>Добавление поэмы или стихотворения</title>
</head>
<body>
    <h1 style="text-align: center;">Добавление</h1>
    <form method="POST">
        <input type="text" name="author" id = "author" class="form-control" placeholder="Автор"></br>
        <input type="text" id="namepoem" name="namepoem" class="form-control" placeholder="Название произведения"></br>
        <input type="text" id="poem" name="poem" class="form-control" placeholder="Произведение"></br>
        <input type="submit" class="btn btn-success" value="Отправить">
    </form>
</body>
<script src="https://code.jquery.com/jquery-3.3.1.slim.min.js" integrity="sha384-q8i/X+965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH+8abtTE1Pi6jizo" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js" integrity="sha384-UO2eT0CpHqdSJQ6hJty5KVphtPhzWj9WO1clHTMGa3JDZwrnQq4sF86dIHNDz0W1" crossorigin="anonymous"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js" integrity="sha384-JjSmVgyd0p3pXB1rRibZUAYoIIy6OrQ6VrjIEaFf/nJGzIxFDsf4x0xIM+B07jRM" crossorigin="anonymous"></script>
</html>

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1 answer(s)

I

Ivan Yakushenko, 2021-02-20
@kriventseff

The route should always return something, but in case of an error, it does not return anything in your case. Moreover, due to the fact that you decided to just "silence" the error, you do not know why you have this error, but you could do like this:

import logging

@app.route('/create-poem/', methods=['POST', 'GET'])
def create():
    if request.method == 'POST':
        ...
        try:
            ...
        except Exception:
            logging.exception('')
            return ''
    else:
        ...

Then you would see an error that says

sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) no such table: ivan

Then you could open your database and see that it really does not contain the table you need, but it does not exist because you did not create it. But to create a table, you need:

db.create_all()
app.run(debug=True)