On 07/17/2017 09:57 AM, Steve D'Aprano wrote:
collections.namedtuple generates a new class using exec, and records the source
code for the class as a _source attribute.
Although it has a leading underscore, it is actually a public attribute. The
leading underscore distinguishes it from a named field potentially
called "source", e.g. namedtuple("klass", ['source', 'destination']).
There is some discussion on Python-Dev about:
- changing the way the namedtuple class is generated which may
change the _source attribute
- or even dropping it altogether
in order to speed up namedtuple and reduce Python's startup time.
Is there anyone here who uses the namedtuple _source attribute?
My own tests suggest that changing from the current implementation to one
similar to this recipe here:
https://code.activestate.com/recipes/578918-yet-another-namedtuple/
which only uses exec to generate the __new__ method, not the entire class, has
the potential to speed up namedtuple by a factor of four.
I use namedtuple a lot, and never even HEARD of _source.
That said, it sure feels (as someone who hasn't tried it) like there's a
straightforward namedtuple implementation that calls type() directly
rather than having to exec. I know that exec-gunshyness is overblown,
but is there a simple answer as to why it's necessary here?
--
Rob Gaddi, Highland Technology -- www.highlandtechnology.com
Email address domain is currently out of order. See above to fix.
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