Re: [Pymoney-general] Currency's distrib() method

[Facundo B. <fac...@gm...>]

On 7/1/05, Darek Suchojad <ds...@ti...> wrote:

> Then let's add it. We can always get rid of it if it doesn't survive
> the public discussion on the PEP.

OK. We was forgetting another issue here. Some people don't want the
distribution to be to the cent, dime, or whatever, but to a specific
value.

So, here is what I think will be pretty much the final version of
distrib(). Take a look to the examples, because my idea is to include
them as test cases. Please send other examples if you feel that is
good to test other corners of the problem.

----------------------

distrib(nparts=3DNone, proportions=3DNone, LSV=3DNone)

You can call distrib() with nparts XOR proportions. You can not callit
with both of them, neither with none of them. In any case, you also can
pass LSV.

If you call it with ``nparts`` (an integer or something that can be
int()'ed), the system will distribute the amount in that quantity of
parts, in the same proportion::

  >>> Currency(1).distrib(nparts=3D3)
  (Currency('0.33'), Currency('0.33'), Currency('0.34'))
  >>>
  >>> Currency(1).distrib(nparts=3D7)
  (Currency('0.15'), Currency('0.14'), Currency('0.15'), Currency('0.14'),
  Currency('0.14'), Currency('0.14'), Currency('0.14'))

If you call it with ``proportions`` (a tuple or something that can be
tuple()'d; and in each position of the tuple, a Decimal or something
that could be Decimal()'ed), the system will distribute the amount
regarding those proportions::

  >>> Currency(1).distrib(proportions=3D[1,2])
  [Currency("0.33"), Currency("0.67")]
  >>>
  >>> Currency(3).distrib(proportions=3D[2,1,3,3])
  [Currency("0.66"), Currency("0.33"), Currency("1.01"), Currency("1.00")]

``LSV`` means "least significant value, and is the value to which the
system will aproximate the finals results. The default is
``10**(-dec_places)``, so if you have ``dec_places=3D2``, ``LSV`` will be
``0.01`` (which is what we used in the examples above). It must be a
Decimal or something that can be Decimal()'ed.

  >>> Currency(1).distrib(nparts=3D3, LSV=3DDecimal("0.1"))
  (Currency('0.40'), Currency('0.30'), Currency('0.30'))
  >>>
  >>> Currency(1).distrib(nparts=3D7, LSV=3D"0.05")
  (Currency('0.15'), Currency('0.10'), Currency('0.15'), Currency('0.15'),
  Currency('0.15'), Currency('0.15'), Currency('0.15'))
  >>>
  >>> Currency(1).distrib(proportions=3D[1,2], LSV=3D"0.2")
  [Currency("0.40"), Currency("0.60")]
  >>>
  >>> Currency(3).distrib(proportions=3D[2,1,3,3], LSV=3DDecimal("0.15"))
  [Currency("0.60"), Currency("0.30"), Currency("1.05"), Currency("1.05")]

This is needed (at least) in Sweden, where they're used to round to 50
cents when dealing with coins.

----------------

.    Facundo

Blog: http://www.taniquetil.com.ar/plog/
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