Save and Load Theme Preference in Tkinter – Python GUI Dark Mode Persistence

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 How to extend the Dark Mode feature by saving and loading the user’s theme preference using a simple settings.txt file.

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💾 Remember Theme Preference in Tkinter (Dark/Light)

We’ll modify the previous DarkModeApp to:

1. Save the selected theme (light or dark) in settings.txt

2. Read the preference when the app starts

3. Automatically apply the saved theme

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✅ Step-by-Step Implementation

import tkinter as tk
import os

# Theme dictionaries
LIGHT_THEME = {
    "bg": "#ffffff",
    "fg": "#000000",
    "button_bg": "#f0f0f0",
    "entry_bg": "#ffffff"
}

DARK_THEME = {
    "bg": "#2e2e2e",
    "fg": "#ffffff",
    "button_bg": "#3e3e3e",
    "entry_bg": "#4e4e4e"
}

SETTINGS_FILE = "settings.txt"

class DarkModeApp(tk.Tk):
    def __init__(self):
        super().__init__()
        self.title("Dark Mode with Saved Preference")
        self.geometry("300x200")

        self.theme = self.load_theme()

        self.label = tk.Label(self, text="Hello, Tkinter!", font=("Arial", 14))
        self.label.pack(pady=10)

        self.entry = tk.Entry(self)
        self.entry.pack(pady=5)

        self.toggle_btn = tk.Button(self, text="Toggle Dark Mode", command=self.toggle_theme)
        self.toggle_btn.pack(pady=10)

        self.apply_theme()

    def apply_theme(self):
        self.configure(bg=self.theme["bg"])
        self.label.configure(bg=self.theme["bg"], fg=self.theme["fg"])
        self.entry.configure(bg=self.theme["entry_bg"], fg=self.theme["fg"], insertbackground=self.theme["fg"])
        self.toggle_btn.configure(bg=self.theme["button_bg"], fg=self.theme["fg"])

    def toggle_theme(self):
        self.theme = DARK_THEME if self.theme == LIGHT_THEME else LIGHT_THEME
        self.save_theme("dark" if self.theme == DARK_THEME else "light")
        self.apply_theme()

    def save_theme(self, theme_name):
        with open(SETTINGS_FILE, "w") as f:
            f.write(theme_name)

    def load_theme(self):
        if os.path.exists(SETTINGS_FILE):
            with open(SETTINGS_FILE, "r") as f:
                saved = f.read().strip().lower()
                return DARK_THEME if saved == "dark" else LIGHT_THEME
        return LIGHT_THEME  # default

if __name__ == "__main__":
    app = DarkModeApp()
    app.mainloop()

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📂 What This Does

• Reads settings.txt on startup to get the last theme used

• If no file is found, it defaults to Light Mode

• When the user toggles the theme, it updates the file

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🔐 Tip

To make this platform-independent, you could store the file in a user-safe location like:

from pathlib import Path
SETTINGS_FILE = Path.home() / ".tkinter_theme_settings"

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Now that your app remembers the user's theme preference, it's a much more polished and user-friendly product.

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✅ You're all set to continue with Bonus Part 2: Animations & Transitions in Tkinter. 

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