Tkinter Treeview not showing newly inserted items, no errors given

Question

I'm building a desktop application that lets you insert some data into a form and then the data is displayed in a series (3) of Treeview widgets. This is the form that I'm using to enter new data:

It's in a Toplevel widget. When the Add button is pressed the new data is stored in a file and it also should insert the new data in the corresponding Treeview Widget. This is the root window:

It's comprised of 3 Treeview widgets. The purpose of the application is to give the user the opportunity to sort candidates into the right Treeview widget. The issue that I'm facing is that when the Add button is pressed the new data is not shown in the Treeview widget and no errors are given. I think it may be an issue of class instantiation. This is an excerpt from my app, please see below a Minimal, Complete and Verifiable example

class MainApp(tk.Tk):
    def __init__(self, *args, **kwargs):
        ...
        # frame and menu classes are instantiated here
        self.FrameList = {ViableCandidates: ViableCandidates(self),
                          NotViableCandidates: NotViableCandidates(self),
                          InProgressCandidates: InProgressCandidates(self)}
        ...
    def InstanceLinker(self, frame):
        link = self.FrameList[frame]
        return link
class GUIMenu(tk.Menu):
    def __init__(self, parent):
        ...
    # menu code is here
    addcandidates.add_command(label='Quick Add', command=lambda: QuickAdd(parent))
class QuickAdd(tk.Toplevel):
    def __init__(self, parent):
        ...
    # code for the small Toplevel window
    ...
    # this is the code that I use to add the new item to Treeview when the Add button is pressed
    if CandidateInfo['status'] == 'Viable':
        app.InstanceLinker(ViableCandidates).AddtoList()
    elif CandidateInfo['status'] == 'Not Viable':
        app.InstanceLinker(NotViableCandidates).AddtoList()
    else:
        app.InstanceLinker(InProgressCandidates).AddtoList()
# ViableCandidates, NotViableCandidates, InProgressCandidates are created with the same pattern
class InProgressCandidates(tk.Frame):
    def __init__(self, parent):
        global Counter
        tk.Frame.__init__(self, parent)
        self.columnconfigure(0, weight=1)
        self.rowconfigure(1, weight=1)
        title = tk.Label(self, text="Candidates In Progress", font="Verdana 10 bold")
        title.grid(row=0, column=0, sticky='nesw')
        self.tree = ttk.Treeview(self)
        self.tree.grid(row=1, column=0, sticky='nesw')
        scrollbar = ttk.Scrollbar(self, orient='vertical', command=self.tree.yview)
        scrollbar.grid(row=1, column=1, sticky='nws')
        self.tree.config(columns=('Name', 'Date'), selectmode='browse', height=20, yscrollcommand=scrollbar.set)
        self.tree.column('#0', width=20, minwidth=10, stretch=tk.YES)
        self.tree.column('Name', width=150, minwidth=10, stretch=tk.YES)
        self.tree.column('Date', width=80, minwidth=10, stretch=tk.YES)
        self.tree.heading('#0', text='#', anchor=tk.W)
        self.tree.heading('Name', text='Name', anchor=tk.W)
        self.tree.heading('Date', text='Date', anchor=tk.W)
        if Counter < 4:
            Counter += 1
            self.PopulateList()
    def PopulateList(self):
        selection = Database().SelectFromDB('name, date', "status = 'In progress'")
        for i in range(len(selection)):
            name = list(selection[i])[0]
            date = adjusttotimezone(list(selection[i])[1])
            self.tree.insert("", i, name, text=i + 1)
            self.tree.set(name, 'Name', name)
            self.tree.set(name, 'Date', date)
            CandidateCounter['InProgressCandidates'] = i
    def AddtoList(self):
        CandidateCounter['InProgressCandidates'] += 1
        print('I was here')
        self.tree.insert("", CandidateCounter['InProgressCandidates'], CandidateInfo['name'],
                         text=CandidateCounter['InProgressCandidates'])
        self.tree.set(CandidateInfo['name'], 'Name', CandidateInfo['name'])
        selection = Database().SelectFromDB('date', "name = '" + CandidateInfo['name'] + "'")
        date = adjusttotimezone(list(selection[0])[0])
        self.tree.set(CandidateInfo['name'], 'Date', date)
app = MainApp()
app.mainloop()

When the "Add" button is pressed there are no errors and "I was here" is printed so the AddtoList method is instantiated, but there are no new items added to Treeview. I did check if the variables that I'm using to create the new Treeview item hold the correct data and they do.

EDIT: This is a Minimal, Complete and Verifiable example:

import tkinter as tk
from tkinter import ttk
Bigbadtext = ''
Counter = 0
class MainApp(tk.Tk):
    def __init__(self, *args, **kwargs):
        self.MainWindow = tk.Tk.__init__(self, *args, **kwargs)
        menu = GUIMenu(self)
        self.config(menu=menu)
        frame = InProgressCandidates(self)
        frame.grid(row=0, column=1, sticky='nesw')
        self.FrameList = {InProgressCandidates:InProgressCandidates(self)}
    def InstanceLinker(self, frame):
        link = self.FrameList[frame]
        return link
class GUIMenu(tk.Menu):
    def __init__(self, parent):
        tk.Menu.__init__(self, parent)
        addcandidates = tk.Menu(self, tearoff=0)
        self.add_cascade(label='Add Candidates', menu=addcandidates)
        addcandidates.add_command(label='Quick Add', command=lambda: QuickAdd(parent))
class QuickAdd(tk.Toplevel):
    def __init__(self, parent):
        tk.Toplevel.__init__(self, parent)
        saysomething = tk.Entry(self)
        saysomething.grid(row=1, column=0)
        def addbutton():
            global Bigbadtext
            Bigbadtext = saysomething.get()
            app.InstanceLinker(InProgressCandidates).AddtoList()
        okbutton = ttk.Button(self, text='Add', command=addbutton)
        okbutton.grid(row=2, column=0)
class InProgressCandidates(tk.Frame):
    def __init__(self, parent):
        tk.Frame.__init__(self, parent)
        self.tree = ttk.Treeview(self)
        self.tree.grid(row=1, column=0, sticky='nesw')
        scrollbar = ttk.Scrollbar(self, orient='vertical', command=self.tree.yview)
        scrollbar.grid(row=1, column=1, sticky='nws')
        self.tree.config(columns='something', selectmode='browse', height=20, yscrollcommand=scrollbar.set)
        self.tree.column('#0', width=20, minwidth=10, stretch=tk.YES)
        self.tree.column('something', width=150, minwidth=10, stretch=tk.YES)
        self.tree.heading('#0', text='#', anchor=tk.W)
        self.tree.heading('something', text='Say something', anchor=tk.W)
    def AddtoList(self):
        global Counter
        Counter += 1
        print('I was here')
        self.tree.insert("", Counter, Bigbadtext, text=Counter)
        self.tree.set(Bigbadtext, 'something', Bigbadtext)
app = MainApp()
app.mainloop()

Answer 1

It is not really an answer but I up voted the question because it solved me a problem. I wanted to add items to the widget but did not want to show it to the user until I finished to populate the tree. But each insert showed right away. Now I create 2 identical widgets, one visible and the other is not, and once it is populated I change between them. Thus even a mistake can have a benefit.

Answer 2

The problem is that you are creating two treeview widgets, and then adding items to the one that is invisible.

You create one here:

frame = InProgressCandidates(self)

Then you create another one here:

self.FrameList = {InProgressCandidates:InProgressCandidates(self)}

Since you've already created one, the one you created should be what goes in self.FrameList:

self.FrameList = {InProgressCandidates:frame}