python 3.x - insert() method seems to fail in a subframe

Question

I am writing a 'change' dialog for records in a database. The 'enter data' dialog (terminErfassen) for the same data records works fine. In order to reuse as much of the existing code I have made a class for Labels and the values. The Entry and Text Widgets are repeated in each of the programs. The dialog 'terminAendern' (change due date) starts with a small window asking for the record number. Pressing the 'lookup' (Daten einlesen) button opens the second window which has the same look as the 'enter data' dialog. Problem: Although the code is identically written, it works for the Entry-Fields in the main frame, and it fails for the Entry fields in the subframes. However I am not sure the Frames are the culprits - it seems just the single item which is not identical in the structure. Here is the code. Rows 0 to 5 get filled with data from the database, the Radiobuttons also work, just the Entries in the subframe have this problem. Find below also an image of the screen.

class TerminAendern(te2.DatenFenster):
    "Termine k?nnen ge?ndert werden. Erweiterung von terminErfassen"
    def __init__(self, el):
        "übernimmt das Fenster aus dem Erfassungsdialog"
        super().__init__()
        self.ROOT.title("Termin ?ndern")
        # Datensatz-Nummer
        self.num_wrt = el["nummer"]
        # die Werte aus der Datenbank in das Fenster setzen

        #--------- row 0 -----------
        #self.art_wrt = tk.StringVar() # Operation zB backup, apt-update, extrahieren
        self.art_wrt.set(el["art"])
        self.ART_EING = tk.Entry(self.FRMEINGAB, textvariable=self.art_wrt, bg='white')
        self.ART_EING.grid(column=1, row=0)
        self.ART_EING.insert(0, el["art"])

        #--------- row 1 -----------
        #self.gertwrt = tk.StringVar() # Rechnername oder Ger?t (BoschNyon)
        self.gertwrt.set(el["geraet"])
        self.GERTEING = tk.Entry(self.FRMEINGAB, textvariable=self.gertwrt, bg='white')
        self.GERTEING.insert(90, el["geraet"])
        self.GERTEING.grid(column=1, row=1)

        #--------- row 2 -----------
        #self.brchwrt = tk.StringVar() # Partition/Gegenstand/Aktion/'': TB2, Karten, apt-update
        self.brchwrt.set(el["bereich"])
        self.BRCHEING = tk.Entry(self.FRMEINGAB, textvariable=self.brchwrt, bg='white')
        self.BRCHEING.insert(0, el["bereich"])
        self.BRCHEING.grid(column=1, row=2)

        #--------- row 3 -----------
        #self.bescwrt = tk.StringVar() # Kurztext
        self.bescwrt.set(el["kurztext"])
        self.BESCEING = tk.Label(self.FRMEINGAB, textvariable=self.bescwrt, bg='lightblue',
                                 text=el["kurztext"],anchor=tk.W, relief=tk.RAISED)
        self.BESCEING.grid(column=1, row=3)

        #--------- row 4 -----------
        #self.haufwrt = tk.IntVar()    # H?ufigkeit
        self.haufwrt.set(el["haeufigkeit"])
        self.HAUFEING = tk.Entry(self.FRMEINGAB, textvariable=self.haufwrt, bg='white')
        self.HAUFEING.insert(0, el["haeufigkeit"])
        self.HAUFEING.grid(column=1, row=4)

        #--------- row 5 -----------
        #self.ist_wrt = tk.StringVar() # Datum: Letzte Durchführung
        dbdatum = el["wann"]
        dbm = dbdatum.find("-", 6)
        dbd = dbdatum[dbm+1:] + "." + str(dbdatum[5:dbm]) + "." + str(dbdatum[:4])
        self.IST_EING = tk.Entry(self.FRMEINGAB, textvariable=self.ist_wrt, bg='white')
        self.IST_EING.insert(0, dbd)
        self.IST_EING.grid(column=1, row=5)

        #--------- row 6 Frame 'Prüfung' -----------
        for val, txt in self.pruefwerte: # (int,str)
            if el["pruefen"] == txt:
                self.prufwrt.set(val)
                break
        self.PRUFEING = {} # leeres Dict
        for val, txt in self.pruefwerte: # (int,str)
            self.PRUFEING[val] = tk.Radiobutton(self.FRMPRUEFG, text=txt, padx=5, pady=2,
                                                variable=self.prufwrt, value=val)
            self.PRUFEING[val].grid(column=0, row=val+1, sticky=tk.W)
            if val == self.prufwrt.get():
                self.PRUFEING[val].select()
        #---- Prüfdatei ----
        if "testen" in el:
            self.testwrt.set(el["testen"])
        else:
            self.testwrt.set("")
        print("testwrt = " + self.testwrt.get())
        self.TESTEING = tk.Entry(self.FRMPRUEFG, textvariable=self.testwrt, bg='white')
        #self.TESTEING.delete(0, tk.END)
        self.TESTEING.insert(0, self.testwrt)
        self.TESTEING.grid(column=4, row=2)
        #--------- row 7 Frame 'Machen' -----------
        if el["machen"] == "manuell":
            self.machwrt.set(0)
            self.skrpwrt.set("")
        else:
            self.machwrt.set(1)
            self.skrpwrt.set(el["machen"])
        self.MACHEING = {} # leeres Dict
        for val, txt in self.machwerte:
            self.MACHEING[val] = tk.Radiobutton(self.FRMMACHEN, text=txt, padx=5, pady=3,
                                                variable=self.machwrt, value=val)
            self.MACHEING[val].grid(column=1, row=val+1, sticky=tk.W)
            if val == self.machwrt.get():
                self.MACHEING[val].select()
        #---- Arbeitsskript ----
        self.SKRPEING = tk.Entry(self.FRMMACHEN, textvariable=self.skrpwrt, bg='white')
        self.SKRPEING.insert(0, self.skrpwrt)
        self.SKRPEING.grid(column=4, row=2)
        #--------- row 8 -----------
        self.ANLTeing = tk.Text(self.FRMEINGAB, height=3, width=80, bg='white')
        self.ANLTeing.insert('1.0', el["anleitung"])
        self.ANLTeing.grid(column=1, row=8, columnspan=3)
        #------------ GRID = Alle aktivieren -----------
        self.FRMPRUEFG.grid(column=0, row=6, columnspan=5, sticky=tk.W)
        self.FRMMACHEN.grid(column=0, row=7, columnspan=5, sticky=tk.W)
        self.FRMEINGAB.grid(row=0)
        #------------
        self.PROGENDEBUTTON = tk.Button(self.FRMSCHALT, text='Quit', bg="red",
                                        command=self.ROOT.quit)
                                        .grid(row=0, column=4, sticky=tk.E, padx=20, pady=4)
        self.FRMSCHALT.grid(row=1)

class DatenAuswahl:
    "Fenster zur Auswahl des Datensatzes"
    def __init__(self):
        self.fenster = tk.Tk()
        self.fenster.title('Datensatz ausw?hlen')
        self.MYFRAME = tk.Frame(self.fenster, borderwidth=5, relief=tk.RIDGE, pady=4)
        self.satznr = tk.IntVar()
        self.SATZNR_TXT = tk.Label(self.MYFRAME, text="Nummer des Termins ", padx=5, pady=9)
                          .grid(column=0, row=1, sticky=tk.W)
        self.SATZEIN = tk.Entry(self.MYFRAME, textvariable=self.satznr, bg='white')
                       .grid(column=1,row=1)
        self.DATENBUTTON = tk.Button(self.MYFRAME, text="Daten einlesen", bg="lightblue",
                       command=self.DatenLesen) #self.satznr ??
        self.DATENBUTTON.grid(column=0, row=3, padx=20, pady=20)
        self.MYFRAME.grid(row=0)

    def DatenLesen(self):
        """Versucht, den Termin-Satz mit Nummer 'satznr' aus der Datenbank zu lesen,
danach wird das Fenster zur Datenkorrektur ge?ffnet."""
        el = createTerminListe.terminAuslesen(int(self.satznr.get()))
        # Ausgabe der Werte auf demn Bildschirm
        for k in el.keys():
            print(k + " = " + str(el[k]))
        ausgabe = TerminAendern(el)

myprog = DatenAuswahl()
tk.mainloop()

The definition of the frames in the base class is simple:

class DatenFenster:
    'Klasse zur Bearbeitung von Terminen'
    def __init__ (self):
        locale.setlocale(locale.LC_ALL, 'de_DE.utf8')

        self.ROOT = tk.Tk()
        self.ROOT.title("Termin erfassen")
        self.FRMEINGAB = tk.Frame(self.ROOT, borderwidth=5, relief=tk.RIDGE, pady=4)
        self.FRMPRUEFG = tk.Frame(self.FRMEINGAB, borderwidth=2, relief=tk.RIDGE)
        self.FRMMACHEN = tk.Frame(self.FRMEINGAB, borderwidth=2, relief=tk.RIDGE)
        self.FRMSCHALT = tk.Frame(self.ROOT, borderwidth=4, relief=tk.RAISED, pady=4, padx=6,
                                  bg="orange")
--etc.---

'terminAendern' window

The Entry at 'Prüfdatei (Pfad)' is filled with a default instead of the supplied value from the database.

I have no idea where to look further (apart from the tk source, which I am not sure I can master). I'd be happy if someone could tell me what I am missing.

Answer 1

I found the source of my problem myself. First, a StringVar() created in one Tk() is not visible in another Tk(): see here. Of course, I detected this problem in my code. I have now 2 ways of resolution: (1) to make my 'change'-dialog and my 'enter' dialog two separate programs, i.e. not reusing code. I did not intend this, but it may lead me to a running solution quicker. (2) to use Toplevel(). This would allow me to keep the original program dependencies and to avoid duplicating code, but I did not find a lot of explanations on multi-window programming so far. Anyway, my problem is explained even if not solved.