macOS/Python: Get dimension info about active screens

screen_info.py

from AppKit import NSScreen, NSDeviceSize, NSDeviceResolution
from Quartz import CGDisplayScreenSize

for i, screen in enumerate(NSScreen.screens(), 1):
    description = screen.deviceDescription()
    pw, ph = description[NSDeviceSize].sizeValue()
    rx, ry = description[NSDeviceResolution].sizeValue()
    mmw, mmh = CGDisplayScreenSize(description["NSScreenNumber"])
    scaleFactor = screen.backingScaleFactor()
    pw *= scaleFactor
    ph *= scaleFactor
    print(f"display #{i}: {mmw:.1f}×{mmh:.1f} mm; {pw:.0f}×{ph:.0f} pixels; {rx:.0f}×{ry:.0f} dpi")

Example output:

display #1: 609.6×345.1 mm; 3840×2160 pixels; 72×72 dpi
display #2: 286.4×179.0 mm; 3360×2100 pixels; 144×144 dpi