aio.py 文件源码

def mode_to_flags(mode: str):
    if len(set("awrb+") | set(mode)) > 5:
        raise ValueError('Invalid mode %s' % repr(mode))

    if len(set(mode) & set("awr")) > 1:
        raise ValueError('must have exactly one of create/read/write/append mode')

    flags = 0
    flags |= os.O_NONBLOCK

    if '+' in mode:
        flags |= os.O_CREAT
    if "a" in mode:
        flags |= os.O_RDWR
        flags |= os.O_APPEND
    elif "w" in mode:
        flags |= os.O_RDWR
    elif "r" in mode:
        flags |= os.O_RDONLY

    return flags