Fixes issue #16409: The reporthook callback made by the legacy
urllib.request.urlretrieve API now properly supplies a constant
non-zero block_size as it did in Python 3.2 and 2.7. This matches the
behavior of urllib.request.URLopener.retrieve.
diff --git a/Doc/library/urllib.request.rst b/Doc/library/urllib.request.rst
index 898fe71..21255e5 100644
--- a/Doc/library/urllib.request.rst
+++ b/Doc/library/urllib.request.rst
@@ -1305,7 +1305,8 @@
*filename* is not given, the filename is the output of :func:`tempfile.mktemp`
with a suffix that matches the suffix of the last path component of the input
URL. If *reporthook* is given, it must be a function accepting three numeric
- parameters. It will be called after each chunk of data is read from the
+ parameters: A chunk number, the maximum size chunks are read in and the total size of the download
+ (-1 if unknown). It will be called once at the start and after each chunk of data is read from the
network. *reporthook* is ignored for local URLs.
If the *url* uses the :file:`http:` scheme identifier, the optional *data*