Move deque elements right or left without manually rebuilding it.
What You Will Learn
rotate(n) moves items n positions to the right; negative values rotate left. It changes the deque in place and returns None.
Time complexity assumes a specific input structure. Include setup work such as sorting or building a lookup table when comparing complete solutions.
Step-by-Step Example
The example below makes the behavior visible with small input values that you can change safely.
from collections import deque
schedule = deque(['morning', 'noon', 'night'])
schedule.rotate(1)
print(list(schedule))
schedule.rotate(-1)
print(list(schedule))How the Example Works
- The imports provide the standard-library tools used in the demonstration: collections.
- The variable schedule holds the result of deque(['morning', 'noon', 'night']). Later lines use that value or inspect how it changes.
- The print() calls make the return values or state visible so you can compare them with the explanation and check your prediction.
Expected output from the example:
['night', 'morning', 'noon']
['morning', 'noon', 'night']When You Would Use This
This technique matters when a program handles larger queues, sorted records, or repeated lookups. Choose the data structure based on actual operations and the preconditions the algorithm requires. Verify boundary inputs before optimizing for speed.
Practice: Modify the Code
Rotate on-call shifts one step each day.
Verify the changed output against the behavior described above, including the relevant invalid or boundary case.
For complete parameters and version details, consult the official Python documentation.
Common Beginner Mistakes
- Assuming rotate() creates a new deque or uses positive n for a left rotation.
- Assuming the operation has the same behavior for missing values, empty inputs and regular inputs.
Key Takeaways
- Move deque elements right or left without manually rebuilding it.
- rotate(n) moves items n positions to the right; negative values rotate left.
- Apply this operation only after checking the assumptions and input conditions shown in the example.