l1 = ['a','b','c','d',e','f','g']
l2 = ['h','i','j','k','E-mail:123abc@qq.com','l'.'m',n']
l3 = ['o','p','q','邮箱：xyz456@gmail.com','r','s','t']
l4 = ['u','v',w','x','hmlihh654@163.com abcdefghi','y','z']
请问要如何用正则表达式才能提出所有的邮箱，得到[None,'123abc@qq.com','xyz456@gmail.com','hmlihh654@163.com']的列表？
re.findall('\'([A-Za-z0-9]+@[A-Za-z0-9.]+)\'',str (需要替换的对象))