python-RuntimeError:没有这样的列：inf

我有一条路线，上面说错误在80号线上，但看起来一切正常。当我运行它时，它会显示RuntimeError:no-this-column:inf。我以前从未见过这个，所以有人有什么建议吗？

@app.route("/buy", methods=["GET", "POST"])
@login_required
def buy():
    # If method is get, go to the html file
    if request.method == "GET":
        return render_template("buy.html")
    #declare global variables
    #get the amount of shares
    shares = int(request.form.get("shares"))
    # get the symbol of the stock
    sym = request.form.get("symbol")
    # get the user id for the session
    uid = session["user_id"]
    # get the user cash by looking at their user id
    userMoney = db.execute("SELECT cash FROM users WHERE id = :user_id", user_id = uid)[0]["cash"]
    # lookup the stock symbol from the function in helpers.py
    symbol = lookup(sym)
    # get the purchase value of the stock and all the shares
    purchaseVal = shares * symbol["price"]
    # get the date & time to put it in the table
    currentDate = datetime.datetime.now()
    #check to make sure that all values exist
    if not symbol:
        return apology("That symbol doesn't exist")
    if int(shares) < 0:
        return apology("Only positive shares!")
    # if userCash < int(purchaseVal):
    #     return apology("Not enough money to purchase!")
    #get the new user cash after purchasing the stock
    newCash = userMoney - purchaseVal
    db.execute("UPDATE users SET cash = ? WHERE id = ?", newCash, uid)
    #update the table
    db.execute("INSERT INTO purchases (user_id, shares, symbol, price, date) VALUES(?, ?, ?, ?, ?)", uid, shares, sym, purchaseVal, currentDate)

    # display a successful purchase message using flash function that was included above
    flash("Successful!")
    #redirect to home page after purchasing
    return redirect("/")

完整错误：文件“/工作区/97107415/财务/助手。“py”；，第34行，在“U函数返回f（*args，**kwargs）文件”中/Workspace/97107415/finance/app。“py”；，第80行，在buy db中。执行（“更新用户设置现金=？其中id=？”，newCash，uid）文件/usr/local/lib/python3。10/站点包/cs50/sql。“py”；，第27行，在decorator return f（*args，**kwargs）文件中/usr/local/lib/python3。10/站点包/cs50/sql。“py”；，第398行，执行raise RUNTIMERROR:没有这样的列：inf