[issue5191] Partial function application 'from the right'

[Ben North]

New submission from Ben North <bennorth at users.sourceforge.net>:

The functools module includes a 'partial' class, which allows partial
function application either by positional arguments or keyword
arguments.  However, it cannot be used to create, for example, a
function splitting a string on commas, or a function to extracts logs to
base 10.  I posted

   http://mail.python.org/pipermail/python-dev/2009-January/085638.html

which suggested a 'partial_right' feature, such that the following would
work:

   >>> import functools, math

   >>> split_comma = functools.partial_right(str.split, ',')
   >>> split_comma('a,b,c')
   ['a', 'b', 'c']

   >>> log_10 = functools.partial_right(math.log, 10.0)
   >>> log_10(100.0)
   2.0

There was some useful discussion, but generally the feeling was that the
extra complexity outweighed the potential benefits.  Also, chained
partial applications were troublesome.

The overlap in functionality between 'partial_right' and an existing
patch (#1706256) to allow skipping of positional arguments was raised.

I think the present issue should probably be closed/rejected, but it was
suggested on the mailing list that having the issue and patch on the
record might be useful.  Patches are against 2.6.1 source.

----------
messages: 81457
nosy: bennorth
severity: normal
status: open
title: Partial function application 'from the right'
type: feature request

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue5191>
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