if no 和 if not

x = None

 if  x is not None:
     print("kong")

if  not x is not None:
    print("kong")

# if not XXX就是 ＝    if XXX ==0
# if XXX       就是＝    if XXX !=0

暂且只能这么理解 if  x is not None

if  x is not None