block.py

#-*- coding:utf-8 -*-


class BlockExit(BaseException):

    def __init__(self, block):
        self.block = block


class Block(object):

    def __enter__(self):
        return self


    def __exit__(self, exc_type=None, exc_value=None, traceback=None):

        if isinstance(exc_value, BlockExit) and exc_value.block is self:
            return True


    def escape(self):
        raise BlockExit(self)



def test():

    with Block() as block:

        for i in range(20):

            print(i)

            if i == 10:
                # with 文抜ける
                block.escape()


    with Block() as outer:

        for i in range(20):

            with Block() as inner:

                for j in range(30):

                    print(i, j)

                    if j == 20:
                        outer.escape()


if __name__ == '__main__':
    test()