Python Tkinter Grid Column width Not expanding need First row not Scorallable

If you want to expand the columns to fit the canvas width, you need to:

• save the item ID of canvas.create_window((0, 0), window=frame3s, ...)
• set the width of frame3s to the same as that of canvas inside the callback of event <Configure> on canvas using canvas.itemconfig()
• set weight=1 on column 0 to 2 using frame3s.columnconfigure()

Below is the updated code:

import tkinter as tk
from tkinter import ttk

root = tk.Tk()
root.title("TEST")
root.geometry("800x600")

frame = ttk.Frame(root)
frame.pack(expand=1, fill=tk.BOTH)

canvas = tk.Canvas(frame)
scrollbar = ttk.Scrollbar(frame, orient="vertical", command=canvas.yview)
canvas.configure(yscrollcommand=scrollbar.set)

frame3s = ttk.Frame(canvas)
frame3s.bind("<Configure>", lambda e: canvas.configure(scrollregion=canvas.bbox("all")))

RCnt = 0
DataRow = {}
LabCnt = 0;
for gh in range(40):
   DataRow[LabCnt] = ttk.Label(frame3s, text=LabCnt, font=("Arial", 16, "bold"), cursor="hand2", justify=tk.CENTER, relief="solid")
   DataRow[LabCnt].grid(row=RCnt, column=0, sticky='ew')
   LabCnt += 1
   DataRow[LabCnt] = ttk.Label(frame3s, text=LabCnt, font=("Arial", 16, "bold"), cursor="hand2", justify=tk.CENTER, relief="solid")
   DataRow[LabCnt].grid(row=RCnt, column=1, sticky='ew')
   LabCnt += 1
   DataRow[LabCnt] = ttk.Label(frame3s, text=LabCnt, font=("Arial", 16, "bold"), cursor="hand2", justify=tk.CENTER, relief="solid")
   DataRow[LabCnt].grid(row=RCnt, column=2, sticky='ew')
   LabCnt += 1
   RCnt += 1

# expand column 0 to 2 to fill the width of the frame
frame3s.columnconfigure((0,1,2), weight=1)

frame.columnconfigure(0, weight=1)
frame.rowconfigure(0, weight=1)

# save the item ID of frame3s
frame_id = canvas.create_window((0, 0), window=frame3s, anchor="nw")

canvas.grid(row=0, column=0, sticky="nsew")
scrollbar.grid(row=0, column=1, sticky="ns")

def _on_mousewheel(event):
   canvas.yview_scroll(int(-1 * (event.delta / 120)), "units")

canvas.bind_all("<MouseWheel>", _on_mousewheel)

# set width of frame3s to the same as that of the canvas
canvas.bind('<Configure>', lambda e: canvas.itemconfig(frame_id, width=e.width))

root.mainloop()  # using .mainloop() instead of while loop