intersection, union, difference, symmetric difference for dictionaries

[MRAB]

On 2014-02-25 21:27, Ben Finney wrote:
> Peter Otten <__peter__ at web.de> writes:
>
>> mauro wrote:
>>
>> > - Dictionaries and sets are both accessed by key
>>
>> but sets have no values
>
> Or rather, sets *only* have values. Dictionaries have keys, sets do not
> have keys.
>
But a dictionary can have duplicate values, a set cannot.