reduce to be removed?

Fredrik Lundh fredrik at
Sun Nov 12 00:14:37 CET 2006

Dustan wrote:

> It's always nice to know there are such good-natured people ready to
> help on this group.

any special reason why you keep pretending that some random wikipedia 
editor knows more about a future Python release than the people that 
develops Python ?

> Anyway, I figured out a way to get the builtin
> function 'sum' to work as I need:
> sum([[1,2,3],[4,5,6],[7,8,9]],  [])

sum() is designed for adding numbers, not sequences.  abusing it
for sequences leads to inefficient code, and extremely bad worst-
case behaviour, since you end up copying the same data over and
over and over again -- the function even checks for strings for
this very reason:

 >>> sum(["123", "456", "789"], "")
Traceback (most recent call last):
   File "<stdin>", line 1, in ?
TypeError: sum() can't sum strings [use ''.join(seq) instead]

(maybe it should check for other well-known containers as well?)

if you care about writing robust code, why not just use a for-loop,
and the list extend method?


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