Unable to delete records from sqlite db using flask with two buttons

Question

In my flask+sqlite app, i have created two buttons for updating and deleting the data respectively. It is working fine for inserting, but when deleting the records, records are not deleting. This is my first learning project with CRUD implementation.

app.py

from flask import Flask, render_template, g, request, redirect, url_for
import sqlite3

app = Flask(__name__)

def connect_db():
    connection = sqlite3.connect('./books.db')
    connection.row_factory = sqlite3.Row
    return connection

def get_db():
    if not hasattr(g, 'sqlite3'):
        g.sqlite3_db = connect_db()
    return g.sqlite3_db

@app.route("/")
def main():
    return render_template('book.html')   

@app.route('/', methods=['POST'])
def delete(book):
    if request.method == "POST":
        if request.form['submit'] == 'delete':
            db = get_db()
            cursor = db.execute("delete from books where book = ?", book)
            db.commit()
    return redirect(url_for('view'))
   
@app.route('/view', methods=["GET"])
def view():
    db = get_db()
    cursor = db.execute('select * from books')
    rows = cursor.fetchall()
    return render_template('view.html', rows=rows)


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

View.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>BookStore</title>
</head>
<body>
 <h1> Use this page for adding,deleting book from records </h1>
<form action="" method="POST" >
   <label for="book">Book</label>
          <input type="text" id="book" name="book"><br><br>
   <label for="author">Author</label>
          <input type="text" id="author" name="author"><br><br>
   <label for="category">Book Category</label>
         <select name="category" id="category">
             <option value></option>
             <option value="Fiction">Fiction</option>
             <option value="Non-Fiction">Non-Fiction</option>
             <option value="Business">Business and Management</option>
             <option value="Biography">Biography</option>
         </select><br><br>
    <button type="submit" name="submit" value="update">update</button>
   <button type="submit" name="submit" value="delete">delete</button>
</form>
</body>
</html>

Possibly the case of the book is different in SQLite than the input? Also, the DB-API specifies that the 2nd argument to .execute() should be a container. So, try instead: db.execute("delete from books where book = ?", (book,)) where the parens/brackets and comma make a tuple. — mechanical_meat
– mechanical_meat, Commented Sep 19, 2021 at 18:54
@mechanical_meat, thanks for the reply, but creating the container with comma and brackets i.e. (book,)) still didn't work. Also, can you please help me to understand with the first line "book is different ion sqlite then input.In my DB i have three columns: book, author, category. — Deepak Mishra
– Deepak Mishra, Commented Sep 19, 2021 at 19:07

Aditya Naitan · Accepted Answer · 2021-09-19 19:43:53Z

1

You have 2 functions (main and delete) for the same endpoint /. And also the book variable in the delete(book) function, its value has never been passed.

 @app.route('/<book>', methods=['POST'])
def delete(book):
    if request.method == "POST":
        if request.form['submit'] == 'delete':
            db = get_db()
            cursor = db.execute("delete from books where book = ?", book)
            db.commit()
    return redirect(url_for('view'))

Try something like this, where you can pass the book name in the URL itself.

answered Sep 19, 2021 at 19:43

Aditya Naitan

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