After this lesson, you will be able to:

• Sort a list in place with .sort() and recognize its None return value.
• Get a sorted new list with sorted() while leaving the original unchanged.
• Sort ascending or descending with reverse=True.
• Reverse the current order of a list without sorting its values.

Sorting and reversing are different operations. Sorting arranges comparable items by value; reversing just flips their existing order.

items.sort() changes the original list and returns None. If you need a separate ordered version, use sorted(items): it creates a new list, even when the input is another sequence such as a tuple. Both default to ascending order; reverse=True produces descending order.

items.reverse() flips the existing order in place; it does not sort anything. Avoid relying on .sort() or .reverse() to produce a returned list.

This lesson uses values that Python can compare directly (numbers with numbers, or strings with strings). Sorting dictionaries by nested fields with a key= function belongs in Pythonic Thinking, after higher-order functions are introduced.

1. Sort a list in place

versions = [5, 2, 4]
versions.sort()
print(versions)

Output:

[2, 4, 5]

The existing list now holds the sorted values.

2. Keep the original list

latencies = [80, 40, 65]
ordered = sorted(latencies)
print(ordered)
print(latencies)

Output:

[40, 65, 80]
[80, 40, 65]

sorted() returns a new list, leaving the source unchanged.

3. Sort highest first

scores = [7, 12, 9]
scores.sort(reverse=True)
print(scores)

Output:

[12, 9, 7]

reverse=True changes the sorting direction.

4. Reverse without sorting

steps = ["compile", "test", "ship"]
steps.reverse()
print(steps)

Output:

['ship', 'test', 'compile']

The sequence is flipped, not alphabetically ordered.

1. ordered = items.sort() stores None, not a sorted list.
2. .reverse() is not equivalent to sorting in descending order.
3. .sort() mutates the original list; prefer sorted() when preserving inputs matters.
4. Mixing incomparable types, such as strings and numbers, in one sort raises TypeError.