How to union nested Sets / A single set from nested sets?
Peter Otten
__peter__ at web.de
Wed Jan 6 08:39:32 EST 2016
mviljamaa wrote:
> I'm forming sets by set.adding to sets and this leads to sets such as:
>
> Set([ImmutableSet(['a', ImmutableSet(['a'])]), ImmutableSet(['b',
> 'c'])])
>
> Is there way union these to a single set, i.e. get
>
> Set(['a', 'b', 'c'])
>
> ?
1 What version of Python are you working with?
Both Python 2.7 and 3.x have built-in set and frozenset types that you
should use.
2 Instead of flattening the nested data I recommend that you avoid nesting
in the first place by using update() instead of add()
>>> x = {"a", "b"}
>>> y = {"b", "c"}
>>> z = {"a", "c", "d"}
>>> result = set()
>>> for subset in x, y, z:
... result.update(subset) # or: result |= subset
...
>>> result
{'b', 'a', 'd', 'c'}
For a fixed number of subsets you can avoid the loop and write
>>> result = set()
>>> result.update(x, y, z)
>>> result
{'b', 'a', 'd', 'c'}
or
>>> x | y | z
{'b', 'a', 'd', 'c'}
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