pset7: check50 error - sell page has all required elements

Question

I'm having an argument with check50 on pset7 finance, when it comes to the SELL part.

The web app works fine and I'm able to sell my stocks. When I run check50, though, it keeps telling me that the sell page doesn't have all the reuired elements (without specifying which one):

I double-checked my code and I double-checked the requirements and they match. The requirements are asking for a select element named "symbol" and an input text element named "shares". I have both as you can see here:

<form action="/sell" method="post">
    <select class="form-control" id="select-sell" name="symbol">
        <option disabled selected value>Selling</option>
        {% for stock in stocks %}
            <option>{{ stock.get('stock')|upper }}</option>
        {% endfor %}
    </select>
    <div class="form-group">
        <input autocomplete="off" class="form-control" name="shares" placeholder="Number of shares to sell" type="text"/>
    </div>
    <button class="btn btn-primary" type="submit">Sell</button>
</form>

While this is what's going on in application.py:

def sell():
"""Sell shares of stock"""

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

    # Ensure number shares was submitted
    if (not request.form.get("shares")
    or not request.form.get("shares").isdigit()
    or float(request.form.get("shares")) < 0):
        return apology("must specify a non negative number of shares to sell", 400)

    # Get cumulative number of shares for selected stock
    shares_sum = db.execute("SELECT SUM(shares) FROM :sid WHERE stock = :selected_stock",
                        sid=str(session["user_id"]),
                        selected_stock=request.form.get("symbol").lower())

    # Check if user has enough shares of the stock he/she is trying to sell
    if float(shares_sum[0].get('SUM(shares)')) < float(request.form.get("shares")):
        return apology("cheeky...you cannot sell stocks that you don't have", 400)
    # if he does and he's not selling all his/her shares
    elif float(shares_sum[0].get('SUM(shares)')) >= float(request.form.get("shares")):
        # Update the cash in the "users" table as well
        update_cash = db.execute("UPDATE users SET cash = cash + :sell WHERE id = :sid",
                      sell = float(request.form.get("shares")) * lookup(request.form.get("symbol"))["price"],
                      sid=session["user_id"])

        # While recording transaction (sale) to dedicated table in database
        db.execute("INSERT INTO :user (stock, unitprice, shares, spent, cash, date, time)"
                            "VALUES (:symbol, :price, :number, :tot, :cash, :datestamp, :timestamp)",
                            user=str(session["user_id"]),
                            symbol=request.form.get("symbol").lower(),
                            price=float(lookup(request.form.get("symbol"))["price"]),
                            number=-float(request.form.get("shares")),
                            tot=-(float(lookup(request.form.get("symbol"))["price"])*float(request.form.get("shares"))),
                            cash=float(db.execute("SELECT cash FROM users WHERE id = :sid", sid=session["user_id"])[0].get("cash")),
                            datestamp=str(datetime.now(timezone('Australia/Sydney')).date()),
                            timestamp=str(datetime.now(timezone('Australia/Sydney')).time()))

    # Redirect user to home page
    return redirect("/")


# User reached route via GET (as by clicking a link or via redirect)
else:
    stocks = db.execute("SELECT DISTINCT stock FROM :sid ORDER BY stock", sid=str(session["user_id"]))
    return render_template("sell.html", stocks = stocks)

I really have no idea what's wrong here (especially 'cause it's working!)

Any help is highly appreciated! Thanks!

Answer 1

The issue here is that, when the index.html page is rendered, the lookup function is returning None for the stock (in this particular case, it's because you are converting your symbols to lowercase before storing them, so check50 is expecting "AAAA" but you've stored "aaaa").

Answer 2

The exception was raised after POSTing to login, before opening the sell page. Meaning your problem is likely in login or index.

Some thoughts on your code:

Do you have a table per user?

    shares_sum = db.execute("SELECT SUM(shares) FROM :sid WHERE stock = :selected_stock",
                        sid=str(session["user_id"]),
                        selected_stock=request.form.get("symbol").lower())

makes me wonder. Maybe you should have a different approach, storing all the transactions with a field user_id in a common transaction table.

When I use aggregate functions like SUM(shares), I usually write it like SELECT SUM(shares) AS 'sum_shares', defining an alias that will be used for the field name. Experience has shown the automatically chosen name sometimes differs from what you'd expect, and specifying one is more reliable.