download.py 文件源码

def _check_download_dir(link, download_dir, hashes):
    """ Check download_dir for previously downloaded file with correct hash
        If a correct file is found return its path else None
    """
    download_path = os.path.join(download_dir, link.filename)
    if os.path.exists(download_path):
        # If already downloaded, does its hash match?
        logger.info('File was already downloaded %s', download_path)
        if hashes:
            try:
                hashes.check_against_path(download_path)
            except HashMismatch:
                logger.warning(
                    'Previously-downloaded file %s has bad hash. '
                    'Re-downloading.',
                    download_path
                )
                os.unlink(download_path)
                return None
        return download_path
    return None