[issue31141] Start should be a keyword argument of the built-in sum

[STINNER Victor]

Change by STINNER Victor :


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resolution: out of date -> duplicate

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[issue31141] Start should be a keyword argument of the built-in sum

[Raymond Hettinger]

Change by Raymond Hettinger :


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resolution:  -> out of date
stage:  -> resolved
status: open -> closed
superseder:  -> Make *start* usable as a keyword argument for sum().

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[issue31141] Start should be a keyword argument of the built-in sum

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:

In 2.6 it was "sequence".

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[issue31141] Start should be a keyword argument of the built-in sum

[STINNER Victor]

STINNER Victor  added the comment:

> I don't think it is worth to allow passing the first argument as a keyword 
> argument.

I concur. Would you mind to add a test to make sure that passing the first 
argument as the "iterable" keyword doesn't work?

"iterable" name comes from the Doc/library/functions.rst documentation and from 
the docstring.

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nosy: +vstinner

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[issue31141] Start should be a keyword argument of the built-in sum

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:

First than to allow this argument be passes by keyword, we mast choose its 
name. See the discussion "Start argument for itertools.accumulate()" on 
Python-ideas 
(https://mail.python.org/pipermail/python-ideas/2018-April/049649.html).

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[issue31141] Start should be a keyword argument of the built-in sum

[Cheryl Sabella]

Cheryl Sabella  added the comment:

Hi Mark,

Are you able to make the Argument Clinic change the Serhiy suggested to come up 
with new benchmarks?  

Thanks!

--
nosy: +csabella

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[issue31141] Start should be a keyword argument of the built-in sum

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

Your tests show that there is a performance regression of getting rid of 
Argument Clinic (in addition to increasing the maintenance cost of the code 
that was generated previously). Try to use the simple Argument Clinic change 
(it can has non-zero cost too, but I expect that its penalty is much smaller).

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[issue31141] Start should be a keyword argument of the built-in sum

[Mark Bell]

Mark Bell added the comment:

I ran some timing tests of the patch I submitted to compare it to the current 
build of Python. Using timit on the current master branch I got:

python.exe -m timeit "sum(())" 1.12 usec per loop
python.exe -m timeit "sum((), 0)"  1.22 usec per loop

And for the patched version:

python.exe -m timeit "sum(())" 1.46 usec per loop
python.exe -m timeit "sum((), 0)"  1.57 usec per loop

However my patch wasn't just the simple argument clinic change suggested by 
serhiy.storchaka, so maybe that would be more efficient and easier to 
understand.

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[issue31141] Start should be a keyword argument of the built-in sum

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

Adding this feature is so easy as moving '/' in Argument Clinic declaration one 
line up. I don't think it is worth to allow passing the first argument as a 
keyword argument.

Check what performance effect of this change on simple calls sum(()), sum((), 
0).

--
nosy: +serhiy.storchaka

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[issue31141] Start should be a keyword argument of the built-in sum

[Raymond Hettinger]

Raymond Hettinger added the comment:

Lisa, would you like to take this one?

--
assignee:  -> lisroach
nosy: +lisroach, rhettinger

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[issue31141] Start should be a keyword argument of the built-in sum

[Steven D'Aprano]

Steven D'Aprano added the comment:

This seems like a reasonable enhancement to `sum` to me.

Since 2.7 is in feature freeze, this can only apply to 3.7.

--
nosy: +steven.daprano
type: behavior -> enhancement
versions:  -Python 2.7

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[issue31141] Start should be a keyword argument of the built-in sum

[Mark Bell]

Changes by Mark Bell :


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type:  -> behavior

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[issue31141] Start should be a keyword argument of the built-in sum

[Roundup Robot]

Changes by Roundup Robot :


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pull_requests: +3055

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[issue31141] Start should be a keyword argument of the built-in sum

[Mark Bell]

New submission from Mark Bell:

The built-in function sum takes an optional argument "start" to specify what 
value to start adding from (defaults to 0). This argument should be a keyword 
argument in order to match the other built-in functions such as:

enumerate(range(10), start=5)

This patch allows users to write:

sum(range(10), start=5)

which previously raised "TypeError: sum() takes no keyword arguments". Since 
the only change is making an optional positional argument into a keyword 
argument, this has no effect on any existing code using the current convention 
of:

sum(range(10), 5)

--
components: ctypes
messages: 299908
nosy: Mark.Bell
priority: normal
severity: normal
status: open
title: Start should be a keyword argument of the built-in sum
versions: Python 2.7, Python 3.7

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