Vedran Čačić added the comment:
The fact that you've forgotten about it is exactly why sum tries to educate you
(despite Python being "the language of consenting adults" in most other
aspects). The problem (why it doesn't do a good job in that aspect) is that
people usually expect sum to act
Phillip M. Feldman added the comment:
I'd forgotten about ''.join; this is a good solution. I withdraw my
comment.
On Mon, Sep 7, 2020 at 3:25 PM Steven D'Aprano
wrote:
>
> Steven D'Aprano added the comment:
>
> Marco, sum should be as fast as possible, so we don't want to type check
>
Marco Paolini added the comment:
I was thinking to just clarify a bit the error message that results from
Py_NumberAdd. This won't make it slower in the "hot" path
doing something like (not compile tested, sorry)
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -2451,8 +2451,13 @@
Steven D'Aprano added the comment:
Marco, sum should be as fast as possible, so we don't want to type check every
single element. But if it is easy enough, it might be worth checking the first
element, and if it fails, report:
cannot add 'type' to start value
where 'type' is the type
Steven D'Aprano added the comment:
As Marco says, the exception message is because the default value for start is
0, and you can't concatenate strings to the integer 0.
You get the same error if you try to concatenate lists:
py> sum([[], []])
TypeError: unsupported operand type(s)
