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Append Set to Set

asked 2022-04-12 17:29:02 +0200

Thrash gravatar image

Consider the sets a={1} and b={2}. As output I want {1,{2}}. I tried

sage: a={1};b={2}
sage: a.add(b)


sage: a.union({b})

but both attempts result in an error:

TypeError: unhashable type: 'set'
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answered 2022-04-12 17:44:17 +0200

rburing gravatar image

updated 2022-04-12 17:52:32 +0200

To circumvent this problem the frozenset (which can't be modified after creation) was invented:

sage: a.add(frozenset(b))
sage: a
{1, frozenset({2})}

Another alternative is to use Sage's Set:

sage: a=Set([1])
sage: b=Set([2])
sage: a.union(Set([b]))
{1, {2}}
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How can I remove frozenset in the output?

Thrash gravatar imageThrash ( 2022-04-12 17:46:41 +0200 )edit

You can't really, unless you make a custom type, or call a custom printing function. I offer SageMath's Set as an alternative.

rburing gravatar imagerburing ( 2022-04-12 17:54:11 +0200 )edit

SageMath's Set is the solution for me, thank you! I didn't know about these two different functions (set and Set) and thought there was only one.

Thrash gravatar imageThrash ( 2022-04-12 18:00:23 +0200 )edit

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Asked: 2022-04-12 17:29:02 +0200

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Last updated: Apr 12