[Numpy-discussion] proper use of __new__
Matthew Brett
matthew.brett at gmail.com
Tue Jul 21 14:41:15 EDT 2009
Hi,
>> I'm the person who removed the reference to thread-safeness in the
>> numpy version of the subclassing docs. I remember at the time going
>> through all the email discussions that led up to the thread-safeness
>> question, and concluding (in discussion with Travis O and others) that
>> there was not an increased threading problem with __new__ but
>> understanding why it came up in the first place. I can't now
>> reconstruct that understanding, I could have a go if y'all want some
>> summary...
>
> Did this occur on the mailing list? Could you provide a link?
Yes, here's the link:
http://mail.scipy.org/pipermail/numpy-discussion/2007-February/025922.html
I remember the argument now. Sturla Molden was pointing out that iff
you modify attributes at the class level in __new__, this is not
thread safe - as happens with any global variable. Usually of course
you don't modify class attributes in the __new__ method, and in that
case, expect no subclass threading problems. The key post from Travis
here:
http://mail.scipy.org/pipermail/numpy-discussion/2007-February/025971.html
Matthew
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