This patch implements part of bug 1372650.

Sometimes a web client will send 2 instances of the same name:

Cookie: mycookie=foo; mycookie=bar

The specs listed here:

http://wp.netscape.com/newsref/std/cookie_spec.html

state that the first one is the one that should be used. The other 
cookies listed are the inherited ones from paths that a prefix of the 
current URL. When this is parsed by the Cookie module, mycookie gets 
set to bar when it should be foo.

This patch changes Cookie.py to only use the first instance of duplicate 
cookies when parsing cookie strings.

That link is misleading and just confuses you. :) Instead read John J. Lee's great explanation at the referenced bug report. I have tested the patch and it works as expected. Without the patch:

>>> c = SimpleCookie('foo=33;foo=34')
>>> print c
Set-Cookie: foo=34

With the patch:

>>> c = SimpleCookie('foo=33;foo=34')
>>> print c
Set-Cookie: foo=33

There should be a unit test though and something in the documentation. The keys dict should be a set instead.

See discussion in issue 1372650.

Even if the patch is still valid there are still no doc or unit test changes.