Python Set Methods
Set methods describe unique membership and relationships between groups. They are useful when order and repeated occurrences are outside the meaning of the data.
Understand the idea
union, intersection, difference, and symmetric_difference return combinations, while update variants mutate. issubset, issuperset, and isdisjoint test relationships. remove and discard differ on absence. Frozenset offers an immutable set variant. Sort values only for a deliberate presentation, not because the set promises positional ordering.
Where to try it
Open this example with Try in playground. The code loads as editable text and does not run until you select Run. The first run downloads Python. Each run starts fresh; temporary files created by a script are not files on your PC.
A worked example
first = {"web", "python"}
second = {"python", "data"}
print(sorted(first & second))
print(first.isdisjoint({"sql"}))
Read the result
The intersection is ['python'], and the disjointness test is True.
Try one change
Compute elements in exactly one input and explain why direction matters for ordinary difference.
Quick lookup
| Operation | Meaning and limit |
|---|---|
add / update | Add one hashable element or elements from an iterable. |
remove / discard / pop / clear | Mutating removals with different absence and return contracts. |
union / intersection / difference / symmetric_difference | New sets representing either, shared, left-only, or exactly-one membership. |
intersection_update / difference_update / symmetric_difference_update | Mutate the receiving set with the corresponding operation. |
issubset / issuperset / isdisjoint | Boolean relationship tests. |
copy / frozenset | Shallow set copy or an immutable set value. |