set.add() Add element
Last updated: 2026-09-22
set.add() Add element
set.add(elem) adds elem to the set; no-op if already present. Mutates in place.
| Category | Set Methods |
|---|---|
| Kind | Built-in Type Method |
| Python Version | all |
📝 Syntax
set.add(elem)⚙️ Parameters
| elem Required | The element to add; no-op if already present. |
|---|
Returns：None (adds elem to the set in place).
Mutates the original：Yes (in place)
▶ Example
Edit the code, press Run, and see the result in the output panel:
Output：
{1, 2, 3}💡 Related Cases
More case studies coming soon — check back later.
❓ FAQ
QWhat requirement do the elements added by add() have?
AThey must be hashable (immutable): numbers, strings, and tuples are fine; lists and dicts raise TypeError: unhashable type: 'list'.
QWhat happens when adding an element that already exists?
ASets guarantee uniqueness, so re-adding has no effect and does not raise an error.
QWhat does add() return?
ANone; it modifies the set in place.
