Example:

>>> stuff = {'duck': 4, 'spam': 2}
>>> more_stuff = {'ribbon': 3, 'egg': 1}
>>> all_the_stuff = {**stuff, **more_stuff}
>>> all_the_stuff
{'egg': 1, 'duck': 4, 'spam': 2, 'ribbon': 3}

This is functionally equivalent to:

>>> all_the_stuff = {}
>>> all_the_stuff.update(stuff)
>>> all_the_stuff.update(more_stuff)
>>> all_the_stuff
{'egg': 1, 'duck': 4, 'spam': 2, 'ribbon': 3}

This feature came out of PEP 448.

This is actually a nudge to encourage everyone to upgrade to the latest Python 3.5! I know that not everyone can upgrade due to work difficulties and legacy code, but hopefully this feature will make you consider taking up that battle a little sooner.

If you cannot upgrade to Python 3.5, I wrote about a few other ways you can merge dictionaries in older versions of Python.