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inspection

set.issubset

Returns True if every element of s is also in other. Method form accepts any iterable; <= requires a set. Use < for strict (proper) subset.

s.issubset(other)  |  s <= other

Parameters

Parameter Purpose
other An iterable (method) or set (operator) to test against
returns bool

Examples

>>> {1, 2}.issubset({1, 2, 3})
True

Every element of the left is in the right.

>>> {1, 2} <= {1, 2}
True
>>> {1, 2} < {1, 2}
False

<= allows equality; < is strict/proper subset.

>>> {1, 2}.issubset([1, 2, 3, 4])
True

Method form accepts any iterable.

>>> set().issubset({1, 2})
True

The empty set is a subset of every set.

Gotcha

<= and < require a set on the right; use .issubset() for a list or generator. Every set is a subset of itself; the empty set is a subset of everything.

Related methods

set.issuperset
Returns True if every element of other is in s. Method form accepts any iterable; >= requires a set. Use > for strict (proper) superset.
set.isdisjoint
Returns True if s and other share no elements. Accepts any iterable; there is no operator form.

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