macos 莫名失去焦点

执行下述 python 代码，观测除了当前应用程序外，还有谁占用了焦点

#!/usr/bin/python

from AppKit import NSWorkspace
import time
t = range(1,100)
for i in t:
    time.sleep(3)
    activeAppName = NSWorkspace.sharedWorkspace().activeApplication()['NSApplicationName']
    print activeAppName

查看输出即可