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[Python-Dev] [Python-checkins] cpython: Add optional *func* argument to itertools.accumulate().

Daniel Stutzbach stutzbach at google.com
Mon Mar 28 06:11:04 CEST 2011 
On Sun, Mar 27, 2011 at 6:52 PM, raymond.hettinger <
python-checkins at python.org> wrote:

> -.. function:: accumulate(iterable)

+.. function:: accumulate(iterable[, func])
>


>     Make an iterator that returns accumulated sums. Elements may be any
> addable
> -    type including :class:`Decimal` or :class:`Fraction`.  Equivalent to::
> +    type including :class:`Decimal` or :class:`Fraction`.  If the optional
> +    *func* argument is supplied, it should be a function of two arguments
> +    and it will be used instead of addition.
>

Is there a good use-case for the func argument?  I can only think of bad
use-cases (where "func" does something that does not remotely resemble
addition).  I fear that people will actually implement these bad use-cases,
and I will have to try to read and understand their code.

Adding the func argument seems analogous to adding a func argument to sum(),
which would give it all of the power of reduce().

-- 
Daniel Stutzbach
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