In mathematical notation, union is defined as:
And using Venn diagram:
union()
accepts set-like objects as the other
parameter. It requires this
to be an actual Set
instance, because it directly retrieves the underlying data stored in this
without invoking any user code. Then, it iterates over other
by calling its keys()
method, and constructs a new set with all elements in this
, followed by all elements in other
that are not present in this
.
The order of elements in the returned set is first those in this
followed by those in other
.