contextlib.ContextDecorator

import contextlib


# @contextlib.contextmanager
# def tag(name):
#     print('<{}>'.format(name))
#     yield
#     print('</{}>'.format(name))

class tag(contextlib.ContextDecorator):
    def __init__(self, name):
        self.name = name
        self.start_tag = '<{}>'.format(name)
        self.end_tag = '</{}>'.format(name)

    def __enter__(self):
        print(self.start_tag)

    def __exit__(self, exc_type, exc_val, exc_tb):
        print(exc_type)
        print(exc_val)
        print(exc_tb)
        print(self.end_tag)


with tag('h2'):
    raise Exception('error')
    print('test')

実行結果：

h2>
<class 'Exception'>
error
<traceback object at 0x7fa12715e0f0>
</h2>
Traceback (most recent call last):
  File "/Users/hamazakiisao/PycharmProjects/python_programming/lesson.py", line 27, in <module>
    raise Exception('error')
Exception: error