A list of enrolled students excludes those who withdrew.
What You Need to Understand
set.difference(*others) returns a new set containing elements present in the original but absent from every other iterable. It leaves the source set unchanged.
When to Use It
A list of enrolled students excludes those who withdrew.
Step-by-Step Python Example
enrolled = {"Maya", "Noa", "Liam"}
withdrawn = {"Noa"}
remaining = enrolled.difference(withdrawn)
print(sorted(remaining))
print(sorted(enrolled))How the Example Works
Noa is absent from the new set, while the original still contains all three students.
Example Output
['Liam', 'Maya']
['Liam', 'Maya', 'Noa']
[1, 3]A Second Example
Compare this smaller variation with the main example, then experiment with your own values.
online = {1, 2, 3}
local = {2}
print(sorted(online.difference(local)))Important Behavior and Edge Cases
Difference is directional. A.difference(B) and B.difference(A) usually produce different results.
Try It Yourself
Calculate products available online but not in a local store.
Common Beginner Mistakes
- Difference is directional.
A.difference(B)andB.difference(A)usually produce different results. - Using the wrong collection method for this operation without checking whether it mutates the object, returns a result, or raises on missing data.
Key Takeaways
set.difference(*others)returns a new set containing elements present in the original but absent from every other iterable.- Noa is absent from the new set, while the original still contains all three students.
- Difference is directional.