nit for builtin sum doc

[daishiharada]

BPO	1283491
Nosy	@birkenfeld, @birkenfeld, @rhettinger

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/birkenfeld'
closed_at = <Date 2006-10-12.12:33:19.000>
created_at = <Date 2005-09-07.00:18:50.000>
labels = []
title = 'nit for builtin sum doc'
updated_at = <Date 2006-10-12.12:33:19.000>
user = 'https://bugs.python.org/daishiharada'

bugs.python.org fields:

activity = <Date 2006-10-12.12:33:19.000>
actor = 'georg.brandl'
assignee = 'georg.brandl'
closed = True
closed_date = None
closer = None
components = ['None']
creation = <Date 2005-09-07.00:18:50.000>
creator = 'daishiharada'
dependencies = []
files = []
hgrepos = []
issue_num = 1283491
keywords = []
message_count = 7.0
messages = ['26221', '26222', '26223', '26224', '26225', '26226', '26227']
nosy_count = 4.0
nosy_names = ['georg.brandl', 'georg.brandl', 'rhettinger', 'daishiharada']
pr_nums = []
priority = 'low'
resolution = 'fixed'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue1283491'
versions = []

[daishiharada]

the docstring signature for sum in bltinmodule.c
should be changed from:
sum(sequence, start=0)
to:
sum(sequence[, start])
to reflect the current implementation in builtin_sum.

(or else the implementation should be changed
to accept kwargs.)

[rhettinger]

Logged In: YES
user_id=80475

While the proposed change is technically correct, I find the
original to be more informative.

[daishiharada]

Logged In: YES
user_id=493197

This is relatively minor so I don't mean
to push particularly hard, but I'd like to
at least show how the docstring made
me stray:

>>> sum([x] for x in xrange(10))
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
TypeError: unsupported operand type(s) for +: 'int' and 'list'
>>> help(sum)
Help on built-in function sum in module __builtin__:

sum(...)
    sum(sequence, start=0) -> value
    
    Returns the sum of a sequence of numbers (NOT strings) plus the value
    of parameter 'start'.  When the sequence is empty, returns start.

>>> sum([x] for x in xrange(10), start=[])
  File "<stdin>", line 1
SyntaxError: invalid syntax

# The problem above is orthogonal to the issue in this bug,
# but I wonder if at some point we'll be able to write such?

>>> sum(([x] for x in xrange(10)), start=[])
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
TypeError: sum() takes no keyword arguments

# examine lib docs, which give the signature:
# sum( sequence[, start])

>>> sum(([x] for x in xrange(10)), [])
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> 

# examine bltinmodule.c to confirm that
# sum doesn't accept kwargs.

[daishiharada]

Logged In: YES
user_id=493197

This is relatively minor so I don't mean
to push particularly hard, but I'd like to
at least show how the docstring made
me stray:

>>> sum([x] for x in xrange(10))
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
TypeError: unsupported operand type(s) for +: 'int' and 'list'
>>> help(sum)
Help on built-in function sum in module __builtin__:

sum(...)
    sum(sequence, start=0) -> value
    
    Returns the sum of a sequence of numbers (NOT strings) plus the value
    of parameter 'start'.  When the sequence is empty, returns start.

>>> sum([x] for x in xrange(10), start=[])
  File "<stdin>", line 1
SyntaxError: invalid syntax

# The problem above is orthogonal to the issue in this bug,
# but I wonder if at some point we'll be able to write such?

>>> sum(([x] for x in xrange(10)), start=[])
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
TypeError: sum() takes no keyword arguments

# examine lib docs, which give the signature:
# sum( sequence[, start])

>>> sum(([x] for x in xrange(10)), [])
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> 

# examine bltinmodule.c to confirm that
# sum doesn't accept kwargs.

[rhettinger]

Logged In: YES
user_id=80475

"""
>>> sum([x] for x in xrange(10), start=[])
  File "<stdin>", line 1
SyntaxError: invalid syntax

# The problem above is orthogonal to the issue in this bug,
# but I wonder if at some point we'll be able to write such?
"""

FYI, the answer is no. The requirement for parenthesis
cannot change. To see why, parse this: f(g(t) for t in a,
b).

[birkenfeld]

Logged In: YES
user_id=1188172

If we change the function signature in the docstring, we
must include the "defaults to 0" somewhere.

[birkenfeld]

Logged In: YES
user_id=849994

Fixed in rev. 52315.