iTerm2 Script to change the theme automatically based on the system appearance

SyncTheme.py

#!/usr/bin/env python3

import iterm2


async def set_theme(connection, theme):
    # Themes have space-delimited attributes, one of which will be light or dark.
    parts = theme.split(" ")
    if "dark" in parts:
        preset = await iterm2.ColorPreset.async_get(connection, "GitHub Dark")
    else:
        preset = await iterm2.ColorPreset.async_get(connection, "GitHub Light")

    # Update the list of all profiles and iterate over them.
    profiles = await iterm2.PartialProfile.async_get(connection)
    for profile in profiles:
        await profile.async_set_color_preset(preset)


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

iterm2.run_forever(main)