Set union

Provides a concise way to compute the union of two frozensets without converting to mutable sets.

When you need to combine two frozensets and preserve immutability; when working with hashable set objects as dictionary keys or set elements.

Python code using frozenset for immutable set representations, e.g., in caching, graph algorithms, or when frozenset is required as a dict key.

frozenset(iterable1) | frozenset(iterable2)

frozenset(...) | frozenset(...)

iterable1: any iterable of hashable items, iterable2: any iterable of hashable items

• frozenset constructor
• set union operator |
• frozenset.intersection
• frozenset.difference

• frozenset(set1).union(set2) or frozenset(set1 | set2) using mutable set union then converting.

Using | on regular sets returns a mutable set, not frozenset; forgetting that frozenset is immutable and cannot be changed in-place.

frozenset(&) for intersection, frozenset(-) for difference, frozenset(^) for symmetric difference; using mutable set union set1 | set2.

Coming from languages where '+' is used for set union (e.g., some Lisps), may mistakenly use + with frozenset, which raises TypeError.

• frozenset set operations

The result is a new frozenset; original operands remain unchanged. Operator | works only with frozenset or set operands; mixing with non-set types raises TypeError.

Provides an immutable, hashable set suitable for use as a dictionary key or set element.

Think of the pipe as 'union' for frozensets, like set union but immutable.

The result is a new immutable frozenset; original operands remain unchanged. Using | with regular sets yields a mutable set.

Consider using frozenset.union() for explicit intent, or convert to mutable set, union, then refreeze if mutability is needed.