[Python-Dev] Impact of Namedtuple on startup time (original) (raw)

Isaac Morland isaac.morland at gmail.com
Mon Jul 17 09:26:21 EDT 2017

On 17 July 2017 at 08:43, Antoine Pitrou <solipsis at pitrou.net> wrote:

Hello, Cost of creating a namedtuple has been identified as a contributor to Python startup time. Not only Python core and the stdlib, but any third-party library creating namedtuple classes (there are many of them). An issue was created for this: https://bugs.python.org/issue28638 Raymond decided to close the issue because: 1) the proposed resolution makes the "source" attribute empty (or, at least, something else than it currently is). Raymond claims the "source" attribute is an essential feature of namedtuples.

I think I understand well enough to say something intelligent…

While actual references to _source are likely rare (certainly I’ve never used it), my understanding is that the way namedtuple works is to construct _source, and then exec it to create the class. Once that is done, there is no significant saving to be had by throwing away the constructed _source value.

When namedtuple was being considered for inclusion, I actually went so far as to write a proof-of-concept version that worked by creating a class, creating attributes on it, etc. I don’t remember how far I got but the exec version is the version included in the stdlib. I come from a non-Pythonic background so use of exec still feels a bit weird to me but I absolutely love namedtuple and use it constantly. I don't know whether a polished and completed version of my idea could be faster than using exec, but I wouldn't expect a major saving — a whole bunch of code has to run either way. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.python.org/pipermail/python-dev/attachments/20170717/ea716618/attachment.html>

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