python - 能不能只获取网页的header信息，不获取body？ ( Mechanize )

Question

如果我只需要下载自上次下载以来未发生变化的页面怎么办？什么是最好的方法？我可以先获取页面的大小，然后比较决定它是否已更改，如果是，我要求下载否则跳过？

我打算使用 (python) Mechanize 。

Answer 1

请求应该是 HEAD ，不是 GET:

9.4 HEAD

The HEAD method is identical to GETexcept that the server MUST NOT returna message-body in the response. Themetainformation contained in the HTTPheaders in response to a HEAD requestSHOULD be identical to the informationsent in response to a GET request.This method can be used for obtainingmetainformation about the entityimplied by the request withouttransferring the entity-body itself.This method is often used for testinghypertext links for validity,accessibility, and recentmodification.

The response to a HEAD request MAY becacheable in the sense that theinformation contained in the responseMAY be used to update a previouslycached entity from that resource. Ifthe new field values indicate that thecached entity differs from the currententity (as would be indicated by achange in Content-Length, Content-MD5,ETag or Last-Modified), then the cacheMUST treat the cache entry as stale.

请参阅此处 How can I perform a HEAD request with the mechanize library ？