I found out in the docs 3.6, in the class urllib.request.Request, for the input of 'data' data types, it says :

"The supported object types include bytes, file-like objects, and iterables."

But after testing it with data type dict for the 'data' input, I got error of:

"can't concat str to bytes"

It seems the docs should't say the 'data' data types support iterables.

There more detail discussion is at : https://stackoverflow.com/questions/54802272/some-fundamental-concept-used-in-python-docs

Hope this helps, thanks !