A while back my macbook always lost focus to a background process and I wanted to figure out what was drawing it's attention. That's why I created this small piece of code that you run in the background until your focus switches and it prints out what is currently in focus.

FocusTrackerOSX.py

#! /usr/bin/python
from AppKit import NSWorkspace
import time
from datetime import datetime
workspace = NSWorkspace.sharedWorkspace()
active_app = workspace.activeApplication()['NSApplicationName']
print('Active focus:' + active_app)
while True:
    time.sleep(1)
    prev_app = active_app
    active_app = workspace.activeApplication()['NSApplicationName']
    if prev_app != active_app:
        now = datetime.now()
        current_time = now.strftime("%H:%M:%S")
        print(current_time + ' Focus changed to: ' + active_app)