Python Web Input Processing

@app.route("/users/<userid>", methods=["GET", "POST"])

def user(userid):

    if  not "id" in session:
        return redirect("/login")
    if request.method == "GET":
        user_info = fc.guild_user(session["id"], userid)
        if user_info == None:
            abort(404)
        return render_template("user.html", user=user_info)
    else:
        user_info = fc.guild_user(session["id"], userid)
        if user_info == None:
            abort(404)
        form = request.form
        if not "balance" in form:
            abort(400)
        if not form["balance"].isdigit():
            Return "Please enter the balance as a number only."
        if not (0 < int(form["balance"]) <= 10000000):
            Return "You can enter up to 10 million won in balance."
        con,cur = fc.start_db(session["id"])
        cur.execute("UPDATE users SET balance = ? WHERE id == ?;", (form["balance"], userid))
        con.commit()
        con.close()
        return "ok"