Python List Slices: Create vs. Modify – What's the Difference?

Assignment to List Slices: A Mystery Unraveled

Python's documentation explicitly states that slicing a list yields a distinct new list. However, the ability to assign to these slices has puzzled some programmers.

Question 1: How can something that returns something end up on the left side of an expression?

The key lies in distinguishing between two distinct operations: slicing and slice assignment.

Slicing, represented as b = a[0:2], creates a fresh copy of the specified slice from the original list a and assigns it to the new variable b. The original list a remains unaffected.

Question 2: Why is the original list modified when slicing a list supposedly returns a new list?

Slice assignment, on the other hand, behaves differently. It follows the syntax a[0:2] = b. Unlike slicing, it does not return a new list. Instead, it modifies the original list a by replacing the specified slice with the contents of variable b.

Therefore, it's crucial to comprehend the distinction between these two operations when working with list slices. Slicing creates a new list, while slice assignment modifies the original list.

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