tkinter callback through an error: "Index 0 out of range" - sqlite

Question

I searched for hours what the heck is the reason for this error message:
I have a search entry, which update a listbox depending on my search with a callback function:
Listbox:
self.name_search=tk.StringVar()
self.name_search.trace_add('write', self.my_callback)
self.e_name_search_text = tk.Label(search_f, text="Name: ").grid(row=0, column=0, padx=10, pady=5, sticky='E')
self.e_name_search = ttk.Entry(search_f, width = 35, textvariable=self.name_search)
self.e_name_search.grid(row=0, column=1, padx=5, pady=5, sticky='W')
self.lbox = tk.Listbox(search_f, width=35, height=8)
self.lbox.bind("<Double-Button-1>", self.show_name_search)
self.lbox.bind('<Return>', self.show_name_search)
self.scrollbar = tk.Scrollbar(search_f)
self.lbox.grid(row=1, column=1, rowspan=3, padx=10, pady=1)
self.lbox.config(yscrollcommand = self.scrollbar.set)
self.scrollbar.grid(row=1, column=2, rowspan=3, padx=1, pady=1, sticky='ns')
self.scrollbar.config(command=self.lbox.yview)
So If I type my search, the listbox show me a reduced list of values out of my sqlite database, I am interessed in. If I select one with dobble click. Another sqlite query update my comboboxes.
If I select one I get this error:
Exception in Tkinter callback
Traceback (most recent call last):
File "C:\Python38-32\lib\tkinter\__init__.py", line 1883, in __call__
return self.func(*args)
File "D:\... name.py", line 337, in show_name_search
self.e_fax.current(0)
File "C:\Python38-32\lib\tkinter\ttk.py", line 717, in current
return self.tk.call(self._w, "current", newindex)
_tkinter.TclError: Index 0 out of range
Line 337 comes from another function:
def show_name_search(self, event):
self.clear_field()
widget = event.widget
selection = widget.curselection()
indName = widget.get(selection[0])
print(indName)
print("selktierter Wert: {}".format(indName))
self.realName.set(indName)
connection = sqlite3.connect(select_connect_db)
print('Database connected.')
with connection:
cursor = connection.cursor()
cursor.execute("SELECT number, type, prio, id, uniqueid FROM numbers WHERE realName=?;",(indName,))
data = cursor.fetchall()
print(data)
for row in data:
if row[1] == 'home':
self.phone_home.append(row[0])
print('HOME:',self.phone_home)
if row[1] == 'mobile':
self.mobile.append(row[0])
print('Mobile:',self.mobile)
if row[1] == 'work':
self.business.append(row[0])
print(row[0])
print('WORK:',self.business)
if row[1] == 'fax_work':
self.fax.append(row[0])
print(row[0])
print('FAX_WORK:',self.fax)
self.uid_name.set(row[4])
if len(self.phone_home) != 0:
self.e_phone['values'] = self.phone_home
self.e_phone.current(0)
if len(self.mobile) != 0:
self.e_mobile['values'] = self.mobile
self.e_mobile.current(0)
if len(self.business) != 0:
self.e_business['values'] = self.business # Set the value to the new list
self.e_business.current(0) # Set the first item of the list as current item
if len(self.business) != 0:
self.e_fax['values'] = self.fax
self.e_fax.current(0) ### Line 337 - No entry for this value in my sqlite database
Any idea, what I can search for ?

Answer 1

So self.e_faxseems like a ttk.Combobox to me. Consider this code here:
import tkinter as tk
from tkinter import ttk
root = tk.Tk()
values = []
lb = ttk.Combobox(root,values=values)
lb.current(0)
lb.pack()
root.mainloop()
it throughs the same Error:
_tkinter.TclError: Index 0 out of range
and the reason is the list values is empty, insert any regular string in it and it works.
Make sure if you want to set default value that there is an value.
import tkinter as tk
from tkinter import ttk
root = tk.Tk()
values = ['see']
lb = ttk.Combobox(root,values=values)
lb.current(0)
lb.pack()
root.mainloop()