[Python-Dev] Optimization (original) (raw)

Raymond Hettinger raymond.hettinger at gmail.com
Sun Oct 6 00:35:30 CEST 2013

On Oct 5, 2013, at 12:42 PM, Serhiy Storchaka <storchaka at gmail.com> wrote:

Please remember me, what was common decision about CPython-only optimizations which change computation complexity?

IIRC, it is okay optimize C code for just about anything, but we don't want to alter the pure python code after from idiomatic solutions that work on all of the implementations.

For example, there is a string concatenation optimization in the C code, but we still use and advocate str.join() and try not to write code that relies on the optimization. That said, it is nice that less informed users are sometimes saved from an accidental performance trap.

Making bytearray's efficiently pop from the left side is dubious. This isn't a common idiom, nor should it be. Even if all the other implementations could model this behavior, it wouldn't be a good idea to have bytearrays have different performance characteristics than strings. Right now, it is not too hard to roughly explain the performance characteristics of the various container objects, but that would be imperiled a bit by having bytearrays differing from strings in ways other than their size.

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