[FIXED] exception raised in application: TypeError: 'NoneType' object is not subscriptable

Issue

Hellow, I'm new here and need help. I just did my cs50 Finance problem. everything works, you can buy, sell, see price of quotes, see the history of transactions. But when I'm trying to check50 it showes this error. Also in html files I already did '| usd' as recomended. and it showes everything like it should. I know code is big but, check50 section says this - "Be aware that check50 will test your entire program as a whole. If you run it before completing all required functions, it may report errors on functions that are actually correct but depend on other functions."

import os

from cs50 import SQL
from flask import Flask, flash, redirect, render_template, request, session
from flask_session import Session
from werkzeug.security import check_password_hash, generate_password_hash

from helpers import apology, login_required, lookup, usd

# Configure application
app = Flask(__name__)

# Custom filter
app.jinja_env.filters["usd"] = usd

# Configure session to use filesystem (instead of signed cookies)
app.config["SESSION_PERMANENT"] = False
app.config["SESSION_TYPE"] = "filesystem"
Session(app)

# Configure CS50 Library to use SQLite database
db = SQL("sqlite:///finance.db")


@app.after_request
def after_request(response):
    """Ensure responses aren't cached"""
    response.headers["Cache-Control"] = "no-cache, no-store, must-revalidate"
    response.headers["Expires"] = 0
    response.headers["Pragma"] = "no-cache"
    return response


@app.route("/")
@login_required
def index():
    """Show portfolio of stocks"""

    # Main variables
    user_id = session["user_id"]
    user_cash = db.execute("SELECT cash FROM users WHERE id == ?", user_id)[0]["cash"]
    counter = 0
    shares_total = 0
    user_info = db.execute("SELECT user_id, symbol, SUM(shares) as shares, price, total, MAX(timestamp) as timestamp FROM info WHERE user_id == ? AND shares > 0 GROUP BY symbol", user_id)
    counter = len(user_info)

    # MAIN calculation loop
    if counter != 0:
        for j in range(1):
            for i in range(counter):

                symbol = user_info[i]["symbol"]
                price = lookup(symbol)["price"]
                total = price * user_info[i]["shares"]
                cash = user_cash - total

                # This if statement means if there is more symbol and shares the do this
                if counter > 1:
                    shares_total += user_info[i]["total"]

                elif counter == 1:
                    shares_total = user_info[i]["total"]

                db.execute("UPDATE info SET price == ?, total == ? WHERE user_id == ? AND symbol == ?", price, total, user_id, symbol)

            # Select current cash and then incriment
            cash = db.execute("SELECT cash FROM users WHERE id == ?", user_id)[0]["cash"]
            main_total = cash + shares_total

        return render_template("layout.html", user_info = user_info, i=i, counter = counter, total = total, price = price, tottal = main_total, cash = cash)

    else:

        return render_template("layout.html", cash = user_cash, tottal = user_cash, counter = counter)


@app.route("/buy", methods=["GET", "POST"])
@login_required
def buy():
    """Buy shares of stock"""


    if request.method == "GET":
        return render_template("buy.html")

    else:

        user_id = session["user_id"]
        input_shares = request.form.get("shares")
        cash = db.execute("SELECT cash FROM users WHERE id == ?", user_id)[0]["cash"]


        # Erro hendling statements
        try:
            input_shares = int(request.form.get("shares"))

        except ValueError:
            return apology("shares must be a posative integer", 400)

        input_shares = int(input_shares)

        if input_shares <= 0:
            return apology("Shares number should be more then 0")

        if lookup(request.form.get("symbol")) is None:
            return apology("Please enter valid quotes")

        price = lookup(request.form.get("symbol"))["price"]

        if cash < price * input_shares:
            return apology("You don't have enough money")

        symbol = lookup(request.form.get("symbol"))["name"]
        shares = db.execute("SELECT shares FROM info WHERE user_id == ? AND symbol == ?", user_id, symbol)

        # This statemen is for error hendling, it's neccesery because if there is no purchase yet
        # It will purchase some shares and then return
        if len(shares) == 0:

            total = price * input_shares
            cash -= total
            db.execute("UPDATE users SET cash == ? WHERE id == ?", cash, user_id)
            db.execute("INSERT INTO info (user_id, symbol, shares, price, total) VALUES (?, ?, ?, ?, ?)", user_id, symbol, input_shares, price, total)
            db.execute("INSERT INTO history_info (user_id, symbol, shares, price) VALUES (?, ?, ?, ?)", user_id, symbol, input_shares, price)

            flash('You have bought!', 'success')
            return redirect("/")

        elif len(shares) > 0:

            # ar dagaviwydes rom sheamowmo len(shares) im shemtxvevashi tu ki romelime stock bevri yidva gayidvis istoria aqvs
            # da unda vnaxot ramdenad sworad gvichvenebs shares[0]["shares"] tavis monacems!!!!!!!!!!!!!!!!!!!!!!!!!

            shares = db.execute("SELECT shares FROM info WHERE user_id == ? AND symbol == ?", user_id, symbol)
            shares = shares[0]["shares"]

            shares += input_shares

            # Calculate and then Update all of the information into a SQL database
            total = price * shares

            cash = cash - price * input_shares

            db.execute("UPDATE users SET cash == ? WHERE id == ?", cash, user_id)
            db.execute("UPDATE info SET symbol == ?, price == ?, shares == ?, total == ? WHERE user_id == ? AND symbol == ?", symbol, price, shares, total, user_id, symbol)
            db.execute("INSERT INTO history_info (user_id, symbol, shares, price) VALUES (?, ?, ?, ?)", user_id, symbol, input_shares, price)

            flash('You have bought!', 'success')
            return redirect("/")


@app.route("/history")
@login_required
def history():
    """Show history of transactions"""

    # Main variables
    user_id = session["user_id"]
    info = db.execute("SELECT * FROM history_info WHERE user_id == ?", user_id)
    counter = len(info)

    # If there is not purchase yet it will return nothing
    # Main code is inside HTML For loop and if statement
    if not info:
        return render_template("history.html", info = info)
    else:
        for i in range(counter):
            return render_template("history.html", info = info, i = i, counter = counter)


@app.route("/login", methods=["GET", "POST"])
def login():
    """Log user in"""

    # Forget any user_id
    session.clear()

    # User reached route via POST (as by submitting a form via POST)
    if request.method == "POST":

        # Ensure username was submitted
        if not request.form.get("username"):
            return apology("must provide username", 403)

        # Ensure password was submitted
        elif not request.form.get("password"):
            return apology("must provide password", 403)

        # Query database for username
        rows = db.execute("SELECT * FROM users WHERE username = ?", request.form.get("username"))

        # Ensure username exists and password is correct
        if len(rows) != 1 or not check_password_hash(rows[0]["hash"], request.form.get("password")):
            return apology("invalid username and/or password", 403)

        # Remember which user has logged in
        session["user_id"] = rows[0]["id"]

        return redirect("/")

    # User reached route via GET (as by clicking a link or via redirect)
    else:
        return render_template("login.html")


@app.route("/logout")
def logout():
    """Log user out"""

    # Forget any user_id
    session.clear()

    # Redirect user to login form
    return redirect("/")


@app.route("/quote", methods=["GET", "POST"])
@login_required
def quote():
    """Get stock quote."""
    if request.method == "GET":
        return render_template("quote.html")

    else:
        # save user input and give's it to the lookup function
        symbol = lookup(request.form.get("symbol"))

        # take price from lookup function
        value = lookup(request.form.get("symbol"))

        if symbol == None:
            return apology("You need to sign correct Symbol")

        # Take symbol's Name from dict
        symbol = symbol["name"]

        # Take Symbol's Price from dict
        value = value["price"]

        return render_template("quoted.html", symbol=symbol, value=value)


@app.route("/register", methods=["GET", "POST"])
def register():
    """Register user"""

    session.clear()

    name = request.form.get("username")
    password = request.form.get("password")
    confirm = request.form.get("confirmation")

    # this will count, if there is excist username
    check_users = db.execute("SELECT COUNT(*) FROM users WHERE username = ?", name)

    # if there is match count_value dict will return 1
    count_value = check_users[0]['COUNT(*)']

    if request.method == "POST":

        # Chek users registration form
        if not name:
            return apology("user’s input is blank")

        elif not password:
            return apology("Password input is blank")

        elif not confirm:
            return apology("Confirm password input is blank")

        elif password != confirm:
            return apology("Passwords do not match")

        elif count_value != 0:
            return apology("Username already exists")


        # ransform password into hash
        hashed_password = generate_password_hash(password, method='pbkdf2')

        # if there is no apology, then this will insert users information into SQL
        db.execute("INSERT INTO users(username, hash) VALUES(?, ?)", name, hashed_password)

        # Query database for username
        rows = db.execute("SELECT * FROM users WHERE username = ?", name)

        # Remember which user has logged in
        session["user_id"] = rows[0]["id"]

        # this will let user know that registration succesfully complete
        flash('You have successfully registered!', 'success')

        # redirects to homepage
        return redirect("/")

    else:

        return render_template("register.html")


@app.route("/sell", methods=["GET", "POST"])
@login_required
def sell():
    """Sell shares of stock"""

    if request.method == "GET":

        user_id = session["user_id"]
        # Insert symbols with DISTINC method inside html section
        # DISTINC avoides repeted symbols it will SELECT's only once
        quotes = db.execute("SELECT DISTINCT symbol FROM info WHERE user_id == ? AND shares > 0", user_id)

        return render_template("sell.html", quotes = quotes)

    else:

        # Main variables
        user_id = session["user_id"]
        symbol = request.form.get("symbol")
        input_shares = int(request.form.get("sell-shares"))

        if input_shares <= 0:
            return apology("Number should be greater then zero")

        # This is how we can have acces into symbol
        # 12: means select chars from 12th char
        # :-2 select last two char which is ' } and removes
        symbol = symbol[12:][:-2]
        price = lookup(symbol)["price"]
        cash = db.execute("SELECT cash FROM users WHERE id == ?", user_id)[0]["cash"]

        shares = db.execute("SELECT shares FROM info WHERE user_id ==? AND symbol == ?", user_id, symbol)[0]["shares"]

        if shares < input_shares:
            return apology("You don't have that many quotes")

        shares -= input_shares

        # Main calculation and Update SQL data
        profit = input_shares * price
        profit += cash
        db.execute("UPDATE info SET shares = shares - ?, total = ? * ? WHERE user_id == ? AND symbol == ?", input_shares, shares, price, user_id, symbol)
        db.execute("UPDATE users SET cash == ? WHERE id == ?", profit, user_id)
        db.execute("INSERT INTO history_info (user_id, symbol, shares, price) VALUES (?, ?, -?, ?)", user_id, symbol, input_shares, price)


        flash('Sold!', 'success')

        return redirect("/")

I just don't understand why it showes the error. Is it possible that the problem is in the empty list? And this TypeError is caused by that?

Solution

If it says that NoneType object is not subscriptable, that means that you are attempting to subscript ([]) None.

None[anything]

Is guaranteed to raise a TypeError because None doesn’t define __getitem__ (operator[] for cpp people)

Somewhere in the code, you are attempting somevar[somevalue], and somevar is None.

I am unable to determine where without a stacktrace.

Answered By - Hugh Granger