Pre-PEP: Dictionary accumulator methods

[Dan Sommers]

On Sat, 19 Mar 2005 15:17:59 GMT,
"Raymond Hettinger" <vze4rx4y at verizon.net> wrote:

> [Dan Sommers]

>> Curious that in this lengthy discussion, a method name of
>> "accumulate" never came up.  I'm not sure how to separate the two
>> cases (accumulating scalars vs. accumulating a list), though.

> Separating the two cases is essential.  Also, the wording should
> contain strong cues that remind you of addition and of building a
> list.

Agreed, with a slight hedge towards accumulation or tabulation rather
than addition.  I don't think "summation" gets us anywhere, either.

Are the use cases for qty != 1 for weighted averages (that's the only
one I can think of off the top of my head)?  Is something like this:

    def accumulate( self, key, *values ):
        if values == ( ):
            values = 1
        try:
            self[ key ] += values
        except KeyError:
            if type( key ) == int:
                self[ key ] = 1
            else
                self[ key ] = *values

possible?  It's more "klunky" than I thought it would be before I
started typing it out.

Then we'd have these two use cases:

    histogram = { }
    for word in text.split( ):
        histogram.accumulate( word )

and

    org_chart = { }
    for employee in employees:
        org_chart.accumulate( employee.manager, employee.name )

Regards,
Dan

-- 
Dan Sommers
<http://www.tombstonezero.net/dan/>
μ₀ × ε₀ × c² = 1