Detect OS dark mode in Python

Question

I'm writing a small program in python with a GUI that I'm using tkinter for. What I'd like to do is add dark mode support to my program. Mac OS, Ubuntu (at least Gnome) and Windows 10 all have a system-wide setting for "dark mode" that'll make all programs automatically run with a dark theme.

But how do I check that settings (ideally, OS-independant) so my program knows if it needs to render light mode or dark mode? I found a bunch of libraries like darkdetect that'll handle this for MacOS, but I haven't found anything for Ubuntu and Windows 10.

I know that I can use stuff like ttkthemes to create a dark themed design for my program, but how do I know when to enable that? How can a python script running on Windows 10 or on Ubuntu 20.04 figure out if the user enabled the dark mode in the operating system settings?

Ideally I'm looking for a solution / code that'll work on all three operating systems, but if that's not possible (as I suspect) OS-dependant code would be fine as well. I just can't find proper examples for non-MacOS systems anywhere.

user_2776376 · Answer

Quick answer for Windows 10

def detect_darkmode_in_windows(): 
    try:
        import winreg
    except ImportError:
        return False
    registry = winreg.ConnectRegistry(None, winreg.HKEY_CURRENT_USER)
    reg_keypath = r'SOFTWARE\Microsoft\Windows\CurrentVersion\Themes\Personalize'
    try:
        reg_key = winreg.OpenKey(registry, reg_keypath)
    except FileNotFoundError:
        return False

    for i in range(1024):
        try:
            value_name, value, _ = winreg.EnumValue(reg_key, i)
            if value_name == 'AppsUseLightTheme':
                return value == 0
        except OSError:
            break
    return False

It checks if winreg can be imported, if not you are probably not using Windows
The relevant registry key is searched, if not found, it is assumed that dark mode is not enabled
If the registry key is present and the value is set to 0, dark mode is set

user_10364425 · Answer

On macOS, the Dark/Light mode comes under appearance which can be checked by running a simple command defaults read -g AppleInterfaceStyle on the terminal.

On Dark mode the command returns
```
Dark
```
It'll just return Dark meaning AppleInterfaceStyle exist.
On Light mode the same command returns
```
2020-12-18 17:44:21.870 defaults[20253:5665627] 
The domain/default pair of (kCFPreferencesAnyApplication, AppleInterfaceStyle) does not exist
```
By default light mode is enabled so AppleInterfaceStyle doesn't exist and that's why it is returning an error.

We can simply make a function which will return True if the Dark mode is enabled and False if the Light mode is enabled.

import subprocess

def check_appearance():
    """Checks DARK/LIGHT mode of macos."""
    cmd = 'defaults read -g AppleInterfaceStyle'
    p = subprocess.Popen(cmd, stdout=subprocess.PIPE,
                         stderr=subprocess.PIPE, shell=True)
    return bool(p.communicate()[0])

user_8658651 · Answer

On Gnome the dark mode switch is theme-dependent. The following function should work on default themes in Ubuntu 20.04:

import subprocess


def detectDarkModeGnome():
    '''Detects dark mode in GNOME'''
    getArgs = ['gsettings', 'get', 'org.gnome.desktop.interface', 'gtk-theme']

    currentTheme = subprocess.run(
        getArgs, capture_output=True
    ).stdout.decode("utf-8").strip().strip("'")

    darkIndicator = '-dark'
    if currentTheme.endswith(darkIndicator):
        return True
    return False

user_848419 · Answer

I was going to create my own universal function but it looks like someone already made a nice package for all OS: https://pypi.org/project/darkdetect/

import darkdetect

darkdetect.theme()
# Returns 'Dark'

darkdetect.isDark()
# Returns True

darkdetect.isLight()
# Returns False

Detect OS dark mode in Python

4 Answers