Why join() Beats + for Python String Building

Published: 24 February 2026
on channel: Interview Mentor App

Discover why Python's join() method is dramatically faster than concatenating strings with + in a loop. We break down string immutability, the hidden O(n²) cost of repeated concatenation, and how join pre-computes the total length for a single O(n) allocation — a must-know optimization for Python developers and coding interviews.

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