Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.python > #29499

Re: sum works in sequences (Python 3)

Show all headers | View raw

On Wed, 19 Sep 2012 16:41:20 +0200, Franck Ditter wrote:

> Hello,
> I wonder why sum does not work on the string sequence in Python 3 :
> 
>>>> sum((8,5,9,3))
> 25
>>>> sum([5,8,3,9,2])
> 27
>>>> sum('rtarze')
> TypeError: unsupported operand type(s) for +: 'int' and 'str'
> 
> I naively thought that sum('abc') would expand to 'a'+'b'+'c'
> And the error message is somewhat cryptic...
> 
>     franck

Summation is a mathematical function that works on numbers
Concatenation is the process of appending 1 string to another

although they are not related to each other they do share the same 
operator(+) which is the cause of confusion.
attempting to duck type this function would cause ambiguity for example 
what would you expect from

sum ('a','b',3,4)

'ab34' or 'ab7' ?

even 'A' + 7 would return this error for same reason.
 



-- 
It is the nature of extreme self-lovers, as they will set an house on 
fire,
and it were but to roast their eggs.
		-- Francis Bacon

Back to comp.lang.python | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

sum works in sequences (Python 3) Franck Ditter <franck@ditter.org> - 2012-09-19 16:41 +0200
  Re: sum works in sequences (Python 3) Joel Goldstick <joel.goldstick@gmail.com> - 2012-09-19 10:57 -0400
  Re: sum works in sequences (Python 3) Neil Cerutti <neilc@norwich.edu> - 2012-09-19 14:57 +0000
  Re: sum works in sequences (Python 3) Ian Kelly <ian.g.kelly@gmail.com> - 2012-09-19 09:03 -0600
    Re: sum works in sequences (Python 3) Neil Cerutti <neilc@norwich.edu> - 2012-09-19 15:06 +0000
      Re: sum works in sequences (Python 3) Ian Kelly <ian.g.kelly@gmail.com> - 2012-09-19 09:24 -0600
      Re: sum works in sequences (Python 3) Steve Howell <showell30@yahoo.com> - 2012-09-19 08:37 -0700
        Re: sum works in sequences (Python 3) Ian Kelly <ian.g.kelly@gmail.com> - 2012-09-19 12:33 -0600
          Re: sum works in sequences (Python 3) Steve Howell <showell30@yahoo.com> - 2012-09-19 11:43 -0700
    Re: sum works in sequences (Python 3) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-19 16:14 +0000
  Re: sum works in sequences (Python 3) Alister <alister.ware@ntlworld.com> - 2012-09-19 15:07 +0000
    Re: sum works in sequences (Python 3) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-19 16:18 +0000
    Re: sum works in sequences (Python 3) Terry Reedy <tjreedy@udel.edu> - 2012-09-19 14:49 -0400
    Re: sum works in sequences (Python 3) Hans Mulder <hansmu@xs4all.nl> - 2012-09-20 00:25 +0200

csiph-web