> An alternative to the + operator is the pipe | operator, which is used for set union. This suggestion did not receive much support on Python-Ideas.

That's disappointing. It's always been on my Python wish list that dicts would subclass sets, as dicts are essentially sets with values attached. Pretty much everywhere you can use a set you can use a dict and it acts like the set of its keys. For example:

    >>> s = {'a','b','c'}
    >>> d = {i: i.upper() for i in s}
    >>> list(d) == list(s)
    True

Dictionaries have been moving in this more ergonomic direction for a while. Originally, to union two dictionaries you had to say:

    >>> d2 = {'d': 'D'}
    >>>
    >>> d3 = d.copy()
    >>> d3.update(d2)
    >>> d3
    {'a': 'A', 'b': 'B', 'c': 'C', 'd': 'D'}

Nowadays, as the PEP points out, you can just say:

    >>> {**d, **d2}
    {'a': 'A', 'b': 'B', 'c': 'C', 'd': 'D'}

There's no reason you shouldn't have always been able to say d | d2, same as sets. Now I finally get my wish that dictionaries will behave more similarly to sets and they use the wrong set of operators.