auto_switch_theme.py

#!/usr/bin/env python3

import asyncio
import iterm2

THEME_LIGHT = "Tango Light"
THEME_DARK = "Tango Dark"

'''
In iTerm2, in the menu bar go to Scripts > Manage > New Python Script

Select Basic. Select Long-Running Daemon

Give the script a decent name (I chose auto_dark_mode.py)

Save and open the script in your editor of choice.

Copy and paste the script below and save

Go back to iTerm2, go to Scripts in the menu bar and select the script you just saved.

Try toggling Dark mode to see what happens! Reminder it's under Appearance in the System Settings
'''

class AutoSwitchTheme:
    def __init__(self, connection, light="Light Background", dark="Dark Background"):
        self.connection = connection
        self.light = light
        self.dark = dark

    async def get_app(self):
        return await iterm2.async_get_app(self.connection)

    async def get_theme(self) -> str:
        parts = await (await self.get_app()).async_get_theme()
        if len(parts) <= 1:
            return parts[0]
        return ""

    async def set_color_preset(self, theme):
        preset = await iterm2.ColorPreset.async_get(
            self.connection, self.light if theme == "light" else self.dark
        )

        profiles = await iterm2.PartialProfile.async_query(self.connection)
        for partial in profiles:
            await (await partial.async_get_full_profile()).async_set_color_preset(
                preset
            )


async def quit(connection):
    while True:
        if not connection.websocket.open:
            exit(0)
        await asyncio.sleep(1)


async def main(connection):
    asyncio.ensure_future(quit(connection), loop=asyncio.get_event_loop())

    ast = AutoSwitchTheme(connection, THEME_LIGHT, THEME_DARK)
    await ast.set_color_preset(await ast.get_theme())

    async with iterm2.VariableMonitor(
        connection, iterm2.VariableScopes.APP, "effectiveTheme", None
    ) as mon:
        while True:
            # Block until theme changes
            theme = await mon.async_get()

            # Set preset if theme has changed
            await ast.set_color_preset(theme)


try:
    iterm2.run_forever(main)
except:
    print("Unable to connect on iTerm2 application")