Reworking StringIO concatenation in Python

Python string objects are immutable, so changing the value of a string requires that a new string object be created with the new value. That is fairly well-understood within the community, but there are some "anti-patterns" that arise; it is pretty common for new users to build up a longer string by repeatedly concatenating to the end of the "same" string. The performance penalty for doing that could be avoided by switching to a type that is geared toward incremental updates, but Python 3 has already optimized the penalty away for regular strings. A recent thread on the python-ideas mailing list explored this topic some.

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