contextlibの使い方

contextmanagerはデコレーターを with を使用して書けるようにできるしろもの。

from contextlib import contextmanager

@contextmanager
def sample(*args,**kwargs):
    print('start')
    yield
    print('end')

with sample() as f:
    print("hoge")

@contextmanager
def _Stream(path, *args, **kwargs):
    if path == '-':
        yield sys.stdout
    else:
        with open(path, *args, **kwargs) as fp:
            yield fp

def _Print(stream, msg):
    print(msg, file=stream)

# 指定パス以下にテキストを書き出す
with _Stream("D:/sample.txt",'w') as f:
    _Print(f,'sample')

with _Stream("-") as f:
    _Print(f,"hoge")
    _Print(f,"Hello World!!")