Tkinter Desktop Apps

import tkinter as tk
from tkinter import ttk, messagebox

def convert() -> None:
    try:
        celsius = float(temperature.get())
    except ValueError:
        messagebox.showerror("Invalid temperature", "Enter a number.")
        return
    fahrenheit.set(f"{celsius * 9 / 5 + 32:.1f} °F")

root = tk.Tk()
root.title("Temperature Converter")
root.minsize(360, 160)

frame = ttk.Frame(root, padding=20)
frame.grid(sticky="nsew")
root.columnconfigure(0, weight=1)
root.rowconfigure(0, weight=1)
frame.columnconfigure(1, weight=1)

temperature = tk.StringVar()
fahrenheit = tk.StringVar(value="—")

ttk.Label(frame, text="Celsius").grid(row=0, column=0, padx=6, pady=6)
entry = ttk.Entry(frame, textvariable=temperature)
entry.grid(row=0, column=1, sticky="ew", padx=6, pady=6)
ttk.Button(frame, text="Convert", command=convert).grid(row=1, column=0, columnspan=2, pady=8)
ttk.Label(frame, textvariable=fahrenheit, font=("TkDefaultFont", 16)).grid(row=2, column=0, columnspan=2)

entry.focus()
root.bind("<Return>", lambda event: convert())
root.mainloop()

# Useful dialogs and a scrollable list
from tkinter import filedialog

path = filedialog.askopenfilename(
    title="Open a text file",
    filetypes=[("Text files", "*.txt"), ("All files", "*.*")],
)

tree = ttk.Treeview(root, columns=("size",), show="tree headings")
tree.heading("#0", text="Name")
tree.heading("size", text="Bytes")
tree.insert("", "end", text="notes.txt", values=(2048,))

# Schedule work without freezing the window
def update_clock():
    clock.configure(text=time.strftime("%H:%M:%S"))
    root.after(1000, update_clock)

# For slow network/file work, use a worker thread and send the
# result back with root.after(...). Never update widgets from that thread.