COM and currency conversion

[John]

Much appreciated!

-John


"Tim Peters" <tim.one at home.com> wrote in message
news:mailman.989202309.7815.python-list at python.org...
> [John]
> > I've run into another issue with using ADO/SQL Server with Python.
> > It has to  do with how money fields come across in Python. Python
> > converts the money  field into a 2 value tuple. Anyone know the way
> > to get a meaningful dollar  about back out? Here are some examples
> > of dollar amounts and their  representation in Python:    $1,234,567.01
> > == (2, -539231788)  $1,000,000.00 == (2, 1410065408)  $2,000,000.00
> > == (4, -1474836480)
>
> Based on what Mark said later, here's a function that should do the trick:
>
> TWO32 = 2L ** 32
> def tuple_to_100x_pennies((hi, lo)):
>     if lo < 0:
>         lo += TWO32
>     return (long(hi) << 32) + lo
>
> Using your examples,
>
> print map(tuple_to_100x_pennies,
>           ((2, -539231788),
>            (2, 1410065408),
>            (4, -1474836480)))
>
> prints
>
> [12345670100L, 10000000000L, 20000000000L]
>
> Divide by 100 to get pennies; by 10000 to get dollars.
>
> [Mark Hammond]
> > This is a little sad.  Python has no support at all for these.  The
> > basic problem is that there is no Python type to convert it to.
> > It you dig on MSDN, you will find this represents a fixed decimal
> > point number.
> > In the interests of being correct when Tim may be watching <wink> it
> > is exactly:
>
> Way to cover your ass, Mark!  I would have torn you to shreds <wink>.
>
> > "A currency number stored as an 8-byte, two's complement
> > integer, scaled by 10,000 to give a fixed-point number with 15
> > digits to the left of the decimal point and 4 digits to the right.
> > This representation provides a range of 922337203685477.5807 to
> > -922337203685477.5808"
> >
> >   I have discussed this with Tim, and he agrees in general that
> > conversion to float would be evil, and there is no better type.  He
> > has suggested I rip out his "FixedPoint.py"
> > (ftp://ftp.python.org/pub/python/contrib-09-Dec-1999/DataStructures/
> >      FixedPoint.py)
> > and use that.
>
> I still do -- this particular format is just a special case of FixedPoint
> with 4 digits after the decimal point, so should be easy to supply via
> exposing a subclass of FixedPoint.
>
> > However, there is also implication that Python will grow something
> > like this as a core datatype, so I don't want to lock everyone
> > into FixedPoint when something more natural may be just around
> > the corner.
>
> One person said they were going to look into this and was never heard from
> again.  I'd like to implement IBM's proposed standard for decimal
arithmetic
> (http://www2.hursley.ibm.com/decimal/) but have no time for it (and never
> thought I would <wink/sigh>).  Marc-Andre Lemburg started down some sort
of
> related path, but appeared to get distracted by wrapping the entire GNU
> multiprecision library instead (which is way cool for its own sake, but
> doesn't actually supply the decimal currency type he was looking for at
the
> start).
>
> So don't hold your breath -- or at least don't hold mine <wink>.
>
>
>