hookenv.py 文件源码

def relation_get(attribute=None, unit=None, rid=None):
    """Get relation information"""
    _args = ['relation-get', '--format=json']
    if rid:
        _args.append('-r')
        _args.append(rid)
    _args.append(attribute or '-')
    if unit:
        _args.append(unit)
    try:
        return json.loads(subprocess.check_output(_args).decode('UTF-8'))
    except ValueError:
        return None
    except CalledProcessError as e:
        if e.returncode == 2:
            return None
        raise