class Context:
    def __init__(self,name):
        self.name = name
    def __enter__(self):
        print("Entering",self.name)
    def __exit__(self, *args):
        print("Exiting",self.name,"with",[type(x) for x in args])

def nested():
    print("Before")
    with Context('a') as a:
        with Context('b') as b:
            with Context('c') as c:
                print("Hello, world.")
    print("After")

nested()

def simple():
    print("Before")
    with Context('a') as a, Context('b') as b, Context('c') as c:
        print("Hello, world.")
    print("After")

simple()


def exceptional():
    print("Before")
    with Context('a') as a, Context('b') as b, Context('c') as c:
        print("Prior")
        raise ValueError("oh no")
        print("Shouldn't happen")
    print("After")

try:
    exceptional()
except Exception as e:
    print("Raised",repr(e))