Seems like the 'reporthook', when provided to the
'retrieve' function of urllib will be called with
(blocknumber, blocksize, totalsize).

However, the call to read() might return *less* than
'blocksize' bytes (I believe), so it should imho be
called with len(block) as the second argument instead.
Or maybe add a fourth argument 'readbytes'.

Attached patch adds new argument: progresshook - it will be passed two
arguments: count of downloaded bytes and total file size (or -1 if it's
not available).

Introducing new argument instead of modifying reporthook maintains
backwards compatibility, also allows removal of reporthook at one point
in the future.

This patch is against r30 SVN tag.

Patch has docs, tests needed.

Simple (lazy) test case added.

It just replicates one test case of reporthook to work with progresshook.

The testcases assume the hard-coded value of blocksize on urllib, maybe it should become a public property.

Also commented on diff: http://bugs.python.org/review/1490929/show

Related issue 16409

The code in urllib is different now but I see that a test very similar to the one in the patch exists, so was this fixed?

https://github.com/python/cpython/blob/e68c67805e6a4c4ec80bea64be0e8373cc02d322/Lib/test/test_urllib.py#L813

> so was this fixed?

Irit, not really. This is adding another hook called "progress hook" in addition to the "report hook". We need to evaluate if this is really required.