A membership list is copied before testing a proposed change.
What You Need to Understand
set.copy() returns a shallow independent set containing the same elements. Ordinary set elements must be hashable.
When to Use It
A membership list is copied before testing a proposed change.
Step-by-Step Python Example
original = {"basic", "pro"}
proposed = original.copy()
proposed.add("trial")
print(sorted(original))
print(sorted(proposed))How the Example Works
The added tier appears in only the copied set.
Example Output
['basic', 'pro']
['basic', 'pro', 'trial']
{1, 2} {2}A Second Example
Compare this smaller variation with the main example, then experiment with your own values.
original_set = {1, 2}
copied_set = original_set.copy()
copied_set.discard(1)
print(original_set, copied_set)Important Behavior and Edge Cases
Since elements are shared objects, a shallow copy does not duplicate custom element instances. Avoid mutating the equality or hash behavior of set members.
Try It Yourself
Remove an element from the copy while leaving the original intact.
Common Beginner Mistakes
- Since elements are shared objects, a shallow copy does not duplicate custom element instances. Avoid mutating the equality or hash behavior of set members.
- 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.copy()returns a shallow independent set containing the same elements.- The added tier appears in only the copied set.
- Since elements are shared objects, a shallow copy does not duplicate custom element instances.