[python-context-manager] using class and context manager method to implement python context manager #python

using-class.py

class Context(object):
    def __init__(self, name):
        self.file = open(name)

    def __enter__(self):
        return self.file

    def __exit__(self, ctx_type, ctx_value, ctx_traceback):
        self.file.close()

with Context('xxx') as f:
    pass

using-contextlib.py

import contextlib

@contextlib.contextmanager
def custom_open(filename):
    try:
        f = open(filename)
        yield f
    finally:
        f.close()

with custom_open('file') as f:
    pass