[Python-ideas] PEP: Dict addition and subtraction

Steven D'Aprano steve at pearwood.info
Fri Mar 15 11:21:48 EDT 2019

On Fri, Mar 15, 2019 at 11:54:51AM -0300, Andre Roberge wrote:
> On Fri, Mar 15, 2019 at 11:42 AM Steven D'Aprano <steve at pearwood.info>
> wrote:
> > [snip]
> >
> > I still remember being told in no uncertain terms by the core devs that
> > adding a clear() method to lists was a waste of time because there was
> > already a perfectly good way to spell it with slicing. And then ABCs
> > came along and now lists have a clear method. So opinions change too.
> >
> > I agree with the opinions expressed in the (partially) quoted message
> but I don't think that this is how this particular change happened.
> https://mail.python.org/pipermail/python-ideas/2009-April/003897.html

You proposed that in April 2009, but there was nothing added to the bug 
tracker for 18 months until it was finally added by Terry Reedy in 
November 2010, based on discussion in a completely different thread (one 
about sets!):


Contrary-wise, a few years earlier the same request had been roundly 
dismissed by core-devs and Python luminaries as "inane", "redundant" and 


People can change their mind -- something that is dismissed one year may 
be accepted some years later on.


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