FLASK-python ValueError：视图函数未返回响应

Question

I am trying to run an sql function that inserts data into a table. I am following the example explained here but whenever i run the script i get the error "ValueError: View function did not return a response"

My code looks like this:

from flask import render_template, flash, redirect, request
from app import app
from .forms import LoginForm
from .forms import RegistrationForm
import sqlite3 as sql

@app.route('/')
@app.route('/index')


@app.route('/registration', methods = ['GET','POST'])
def registration():
    form = RegistrationForm()

    if request.method == 'POST':
      try:
         card_id = request.form['card_id']
         pin = request.form['pin']
         account_id = request.form['account_id']


         with sql.connect("testDB.db") as con:
            cur = con.cursor()

            cur.execute("INSERT INTO atm_card (card_id,pin,account_id) VALUES (?,?,?,?)",(card_id,pin,account_id) )

            con.commit()
            msg = "Record successfully added"
      except:
         con.rollback()
         msg = "error in insert operation"

      finally:
         return render_template("index.html",msg = msg)
         con.close()

what can i be possibly be doing wrong?

Answer 1

What would be returned if request method is GET? you are rendering template only on POST request. correct it.

@app.route('/registration', methods = ['GET','POST'])
def registration():
    form = RegistrationForm()

    if request.method == 'POST':
      try:
         card_id = request.form['card_id']
         pin = request.form['pin']
         account_id = request.form['account_id']


         with sql.connect("testDB.db") as con:
            cur = con.cursor()

            cur.execute("INSERT INTO atm_card (card_id,pin,account_id) VALUES (?,?,?,?)",(card_id,pin,account_id) )

            con.commit()
            msg = "Record successfully added"
      except:
         con.rollback()
         msg = "error in insert operation"

      finally:
         return render_template("index.html",msg = msg)
         con.close()
    else:
        return render_template('index.html', form=form)