我是Python的新手,并试图了解机器学习。以下是我从Udacity任务获得的代码块。python文件名,_ = urlretrieve(url +文件名,dest_filename,reporthook = download_progress_hook)
def maybe_download(filename, expected_bytes, force=False):
"""Download a file if not present, and make sure it's the right size."""
dest_filename = os.path.join(data_root, filename)
if force or not os.path.exists(dest_filename):
print('Attempting to download:', filename)
filename, _ = urlretrieve(url + filename, dest_filename, reporthook=download_progress_hook)
print('\nDownload Complete!')
statinfo = os.stat(dest_filename)
if statinfo.st_size == expected_bytes:
print('Found and verified', dest_filename)
else:
raise Exception(
'Failed to verify ' + dest_filename + '. Can you get to it with a browser?')
return dest_filename
我可以理解大部分的部分。但是,我很困惑filename, _ = urlretrieve(...)
部分。这个分配是什么?我在调试器中追踪它,发现在此表达式之前或之后filename = '.\\notMNIST_large.tar.gz'
保持不变。
所以我的问题这个filename, _ = urlretrieve(...)
究竟意味着什么?这是一种先进的技术来分配隐藏表达中的价值吗?
'urlretrieve'函数返回2个值。通话后'_'的价值是多少? – gcw