Tkinter Image not Displaying when rendering class objects with multiple frames - python-3.x

Question

I've created a desktop application using Tkinter in python3. There is a main class object 'Stack' for the application and within it is a function to render multiple frames for navigation to other windows within the app on a button click event.
I'm trying to display an image on the 'HomePage' screen (and actually all pages as a heading) using PIL.ImageTk/PIL.Image. Every time I run the app from terminal (macOS), the desktop app runs but the image does not appear. What am I doing wrong? Here is my code:
import getpass
import tkinter as tk
from tkinter import ttk
from PIL import ImageTk, Image
LARGE_FONT = ('Source Code Pro', 24)
class Stack(tk.Tk):
def __init__(self, *args, **kwargs):
tk.Tk.__init__(self, *args, **kwargs)
container = tk.Frame(self)
container.pack(side='top', fill='both', expand=True)
container.grid_rowconfigure(0, weight=1)
container.grid_columnconfigure(0, weight=1)
self.frames = {}
for F in (HomePage, NdA):
frame = F(container, self)
self.frames[F] = frame
frame.grid(row=0, column=0, sticky='news')
self.show_frame(HomePage)
def show_frame(self, cont):
frame = self.frames[cont]
frame.tkraise()
class HomePage(tk.Frame):
def __init__(self, parent, controller):
tk.Frame.__init__(self, parent)
username = getpass.getuser()
logo_path = 'myfilepath'.format(username)
img = ImageTk.PhotoImage(Image.open(logo_path+'myimage.png').resize((120,120)))
l = tk.Label(self, image=img)
l.grid(column=0, row=0, ipadx=10, ipady=5, sticky='w')
ttk.Label(
self,
text='Some Text',
wraplength=450,
justify=tk.LEFT
).grid(
column=1,
row=0,
ipady=10,
padx=(0,10),
sticky='nw')
tier1 = tk.Button(self, text='Button1', state=tk.DISABLED).grid(column=0, row=3, padx=10, columnspan=2, sticky='nesw')
tier2 = tk.Button(self, text='Button2', state=tk.DISABLED).grid(column=0, row=4, padx=10, columnspan=4, sticky='nesw')
tier3 = ttk.Button(self, text='Button3', command=lambda: controller.show_frame(Tier3))
tier3.grid(column=0, row=5, padx=10, columnspan=4, sticky='nesw')
nda = ttk.Button(self, text='Button4', command=lambda: controller.show_frame(NdA))
nda.grid(column=0, row=6, padx=10, pady=(0,10), columnspan=4, sticky='nesw')
class NdA(tk.Frame):
def __init__(self, parent, controller):
tk.Frame.__init__(self, parent)
def clear_form():
effective_date.delete(0, END)
client_name.delete(0, END)
address.delete(0, END)
user_initials.delete(0, END)
def submit_data():
functions.create_nda(
date=effective_date.get(),
client_name=client_name.get(),
address=address.get(),
user=user_initials.get()
)
effective_date.delete(0, tk.END)
client_name.delete(0, tk.END)
address.delete(0, tk.END)
user_initials.delete(0, tk.END)
messagebox.showinfo('Heading Text', 'Message Text')
tk.Label(
self,
text='Some Text',
wraplength=450,
justify=tk.LEFT
).grid(
column=1,
row=0,
columnspan=3,
ipady=10,
padx=(0,10),
sticky='nw')
tk.Label(self, text='Label1').grid(column=0, row=2, pady=(20,10), columnspan=4, sticky='news')
tk.Label(self, text='Data1').grid(column=0, row=3, padx=(10,0), sticky='w')
client_name = tk.Entry(self, width=30)
client_name.grid(column=1, row=3, columnspan=3, padx=(0,10), sticky='news')
tk.Label(self, text='Data2').grid(column=0, row=5, padx=(10,0), sticky='w')
address = tk.Entry(self, width=30)
address.grid(column=1, row=5, columnspan=3, padx=(0,10), sticky='news')
tk.Label(self, text='Data3').grid(column=0, row=6, padx=(10,0), sticky='w')
effective_date = tk.Entry(self, width=30)
effective_date.insert(1, ' mm/dd/yyyy')
effective_date.grid(column=1, row=6, columnspan=3, padx=(0,10), sticky='news')
tk.Label(self, text='Data4').grid(column=0, row=7, padx=(10,0), sticky='w')
user_initials = tk.Entry(self, width=30)
user_initials.grid(column=1, row=7, columnspan=3, padx=(0,10), sticky='news')
create_tier3 = tk.Button(self, text='or click me', command=submit_data).grid(column=3, row=8, pady=(30,10), padx=(0,10), sticky='news')
clear_form = tk.Button(self, text='click me', command=clear_form).grid(column=2, row=8, pady=(30,10), padx=(5,5), sticky='news')
# return_home = tk.Button(self, text='HOME').grid(column=1, row=8, pady=(30,10), sticky='news')
app = Stack()
app.mainloop()

Answer 1

When the __init__() function in class HomePage exits the name img is garbage collected and so the label can't remember it. You need to save a reference to the image. The usual way is to save it as an attribute to the label:
l = tk.Label(self, image=img)
l.image = img # Save reference to image