There is nothing wrong in concatenating two strings with +
. Indeed it’s easier to read than ''.join([a, b])
.
You are right though that concatenating more than 2 strings with +
is an O(n^2) operation (compared to O(n) for join
) and thus becomes inefficient. However this has not to do with using a loop. Even a + b + c + ...
is O(n^2), the reason being that each concatenation produces a new string.
CPython2.4 and above try to mitigate that, but it’s still advisable to use join
when concatenating more than 2 strings.