[Tutor] dollarize.py

[Martin Walsh]

Christopher Spears wrote:
> I'm working on an exercise from Core Python Programming.  I need to create a function that takes a float value and returns the value as string rounded to obtain a financial amount.  Basically, the function does this:
> 
> dollarize(1234567.8901) returns-> $1,234,567,89


> 
> I strip off the symbols, break the string apart, convert it to a float, and then round it.  I'm not sure how to add the commas back after the string has been converted to a rounded float value.  Any hints?
> 

Quick and dirty attempt (and did I mention ugly?) ...

def addcommas(f):
  """
  This amounts to reversing everything left
  of the decimal, grouping by 3s, joining
  with commas, reversing and reassembling.
  """
  # assumes type(f) == float
  left, right = ('%0.2f' % f).split('.')
  rleft = [left[::-1][i:i+3] for i in range(0, len(left), 3)]
  return ','.join(rleft)[::-1] + '.' + right

I think you can also accomplish your broader goal with the locale module
(python2.5), though I don't know it very well.

import sys, locale
def dollarize(s):
    s = ''.join([n for n in str(s) if n not in ('$', ',')])
    if sys.platform == 'win32':
        lcl = 'US'
    else: # linux and mac?
        lcl = 'en_US.UTF8'
    locale.setlocale(locale.LC_MONETARY, lcl)
    return locale.currency(float(s), 1, 1)

print dollarize(12345678.9999)
# $12,345,679.00
print dollarize('123456780.0999')
# $123,456,780.10
print dollarize('$12345670.9999')
# $12,345,671.00
print dollarize('$12,345,678.123')
# $12,345,678.12

HTH,
Marty