javascript – TypeError: The object of type Undefined is not serializable JSON

I have tried SEO in several ways, but I have not been able to correct the error.
Here is my code

HTML

{% extend "layout.html"%} {% block title%} Sell stocks {% endblock%}

{% block main%}


{% if status == 0%}

Please select a stock that you sell.

{% set tuples = session ("stockandbal")%}
{% elif status == 1%} Sold successfully! {% end if %} {% endblock%}

python

@app.route("/sell", methods=("GET", "POST"))
@login_required
def sell():
    username = session("user_id")
    status=0

    session("stockandbal")=dbexe(f"select history.symbol, history.comname, sum(history.sharenum) as totalnum from history join users on users.id=history.user_id where users.username='{username}' group by history.comname having SUM(history.sharenum)>0","selecall")

    if request.method == 'POST':

        symbol=request.form.get("symbol")
        shares=int(request.form.get("shares"))

        resultcom = lookup(symbol) 
        comname=resultcom("name")
        comprice=float(resultcom("price"))
        tAmt= -(comprice*shares)
        balance = int(dbexe(f"select cash from users where username='{username}'", "selec")(0))
        newbal = balance-tAmt

        user_id = int(dbexe(f"select id from users where username='{username}'", "selec")(0))


        dbexe(f"INSERT INTO history('user_id', 'type', 'date', 'symbol', 'comname', 'sharenum', 'sharePrice','transactionAmt', 'balatthetime') VALUES('{user_id}', 'SELL', datetime('now'), '{symbol}','{comname}', {-shares}, {comprice}, {tAmt}, {newbal})", "regi")

        dbexe(f"update users SET cash={newbal} where username='{username}'", "updat")

        status=1
        return render_template("sell.html", status=status)
    else:
        return render_template("sell.html", status=status)

def dbexe(sqlquery, str):
    db = sqlite3.connect("finance.db")
    cur = db.cursor()
    if str == "regi" or str == "updat":
        cur.execute(sqlquery)
        db.commit()
        db.close()
    elif str == "selec":
        rows = cur.execute(sqlquery)
        tupdata = rows.fetchone()
        db.close()
        return tupdata
    elif str == "selecall":
        rows = cur.execute(sqlquery)
        tupdata = rows.fetchall()
        db.close()
        return tupdata

I guess this is the jinja prob used in the Js part. when I print the connection in javascript, it seems that tuplex is Object but it seems indefinite in js as the eorr says. Thank you in advance for your opinions.

vb.net – To be serializable in XML, inherited types of IEnumerable must have an implementation of Add

I use XmlSerializer in VB .Net to convert an object into XML.

When I try to perform the conversion, the following error message is displayed:

InvalidOperationException: To be serializable into XML, the types that inherit from IEnumerable must have an implementation of Add (System.Object) at all levels of their inheritance hierarchy …

Someone knows how I can fix it?

Thank you

Database Theory – Determining whether a schedule is serializable or not

I'm not sure I understand the different types of schedules. I have a calendar is a sequence of transaction transactions. A serial schedule is a schedule in which transactions are executed one after the other. Serializable scheduling is whenever the execution of transactions sequentially, in any order, could have left the database in the same state as the actual schedule. Finally, a conflicting serializable schedule is a schedule in which the order of transaction operations can be changed to make the schedule serial while achieving the same result.

If I have the following schedule $ R_1 (A), R_2 (B), W_1 (B), R_2 (A), W_1 (A), R_2 (B), R_2 (A) $, there is a non-repeatable reading that happens as $ T_2 $ will read different values ​​for $ A $ and $ B $, then the schedule is in serial conflict because we can change the order of operations to make the schedule serially, but how do I determine if the schedule is serial or not?

java – stores and reads serializable files

I'm trying to save String[] in a table and this is saved in an object, but it does allow me to save only one the next one. I'm skipping java.io.EOFException

                private static void AddClient (String nif, String name, String
phone, channel address, floating debt, file) {
MyObjectOutputStream write;
ObjectInputStream read;
Chain[] data = new String[5];
the data[0] = nif;
the data[1] = name;
the data[2] = telephone;
the data[3] = address;
the data[4] = String.valueOf (debt);
try {

ArrayList list = new ArrayList <> ();
if (file.exists ()) {
write = new MyObjectOutputStream (new FileOutputStream (file, true));
read = new ObjectInputStream (new FileInputStream (file));
list = (ArrayList) leer.readObject ();
lista.add (data);
} else {
write = new MyObjectOutputStream (new FileOutputStream (file));
lista.add (data);
}
write.close ();

serialization – What does Order preserve serializable schedules in conflict?

I reviewed the concept of order preservation in the class Conflict Serializable and came across Order preserving conflict serializable (OCSR in short). Here is the OCSR definition that I found:

L & # 39; s history h is the order preserving the serializable conflict if h is a conflict equivalent to a serial history hs where t, t #h: if t occurs completely before t & # 39; in h then the same holds in hs.

Here is an example of planning in OCSR:

w3 (y) c3 w1 (x) r2 (x) c2 w1 (y) c1

But I could not understand why this schedule is in OCSR. From what I understood, it is the conflict graph t3 —> t1 —-> t2

which shows a series calendar where t1 comes before t2. But in the interlaced original program, t2 comes completely before t1. So, how do you say the example given in OCSR?
Can any one help me better understand this?

See the serializable schedule

"Any serializable view planning that is not conflicting must contain blind writing."

(Source: Wikipedia)

Why is this statement true? I have referred to some links like this but I am still not able to visualize the accuracy of the statement above. Help kindly. Thanks in advance.

see serializable and serializable conflict

I have recently solved some problems on this topic and realized that in cases where a conflicting serializable calendar existed; the number of serializable schedules in view was actually equal to the number of serializable conflicting schedules.

I just wanted to check if it's a coincidence that every question I saw showed this property. Or is it really a valid / verified property?