[Python-Dev] sum(...) limitation
tjreedy at udel.edu
Sat Aug 2 08:35:32 CEST 2014
On 8/2/2014 1:57 AM, Allen Li wrote:
> On Fri, Aug 01, 2014 at 02:51:54PM -0700, Guido van Rossum wrote:
>> No. We just can't put all possible use cases in the docstring. :-)
>> On Fri, Aug 1, 2014 at 2:48 PM, Andrea Griffini <agriff at tin.it> wrote:
>> help(sum) tells clearly that it should be used to sum numbers and not
>> strings, and with strings actually fails.
>> However sum([[1,2,3],,,[5,6]], ) concatenates the lists.
>> Is this to be considered a bug?
> Can you explain the rationale behind this design decision? It seems
> terribly inconsistent. Why are only strings explicitly restricted from
> being sum()ed? sum() should either ban everything except numbers or
> accept everything that implements addition (duck typing).
O(n**2) behavior, ''.join(strings) alternative.
Terry Jan Reedy
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