get()方法访问字典

get(keyword, default_arg)

name_for_userid = {
    382: "Alice",
    590: "Bob",
    951: "Dilbert",
}

def greeting(userid):
    return "Hi %s!" % name_for_userid.get(userid, "there")

>>> greeting(382)    # 访问 key 382 ，返回 value
"Hi Alice!"

>>> greeting(333333) # 访问 key 333333，不存在，使用默认value
"Hi there!"