ActiveState Code

Recipe 498181: Add thousands separator commas to formatted numbers

Needed formatted numbers with thousands separator commas added on an end-user report. The usual way mentioned is to use 'module locale.format', but that didn't work cleanly on my Windows machine, and the cure seemed worse than the disease.

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import re

__test__ = {}

re_digits_nondigits = re.compile(r'\d+|\D+')

__test__['re_digits_nondigits'] = r"""

    >>> re_digits_nondigits.findall('$1234.1234')
    ['$', '1234', '.', '1234']
    >>> re_digits_nondigits.findall('1234')
    ['1234']
    >>> re_digits_nondigits.findall('')
    []
    
"""

def FormatWithCommas(format, value):
    """

    >>> FormatWithCommas('%.4f', .1234)
    '0.1234'
    >>> FormatWithCommas('%i', 100)
    '100'
    >>> FormatWithCommas('%.4f', 234.5678)
    '234.5678'
    >>> FormatWithCommas('$%.4f', 234.5678)
    '$234.5678'
    >>> FormatWithCommas('%i', 1000)
    '1,000'
    >>> FormatWithCommas('%.4f', 1234.5678)
    '1,234.5678'
    >>> FormatWithCommas('$%.4f', 1234.5678)
    '$1,234.5678'
    >>> FormatWithCommas('%i', 1000000)
    '1,000,000'
    >>> FormatWithCommas('%.4f', 1234567.5678)
    '1,234,567.5678'
    >>> FormatWithCommas('$%.4f', 1234567.5678)
    '$1,234,567.5678'
    >>> FormatWithCommas('%i', -100)
    '-100'
    >>> FormatWithCommas('%.4f', -234.5678)
    '-234.5678'
    >>> FormatWithCommas('$%.4f', -234.5678)
    '$-234.5678'
    >>> FormatWithCommas('%i', -1000)
    '-1,000'
    >>> FormatWithCommas('%.4f', -1234.5678)
    '-1,234.5678'
    >>> FormatWithCommas('$%.4f', -1234.5678)
    '$-1,234.5678'
    >>> FormatWithCommas('%i', -1000000)
    '-1,000,000'
    >>> FormatWithCommas('%.4f', -1234567.5678)
    '-1,234,567.5678'
    >>> FormatWithCommas('$%.4f', -1234567.5678)
    '$-1,234,567.5678'
    
    """

    parts = re_digits_nondigits.findall(format % (value,))
    for i in xrange(len(parts)):
        s = parts[i]
        if s.isdigit():
            parts[i] = _commafy(s)
            break
    return ''.join(parts)
    
def _commafy(s):

    r = []
    for i, c in enumerate(reversed(s)):
        if i and (not (i % 3)):
            r.insert(0, ',')
        r.insert(0, c)
    return ''.join(r)

Discussion

The recipe works by adding commas to the first contiguous group of digits. It could fail with some odd-ball format that puts extra digits before the number.

Comments

  1. 1. At 7:02 a.m. on 9 oct 2006, ralph heimburger said:

    Another solution. #this solution uses the re module and a single function.

    import re def currency(amount): temp = "%.2f" % amount profile=re.compile(r"(\d)(\d\d\d[.,])") while 1: temp, count = re.subn(profile,r"\1,\2",temp) if not count: break return '$'+temp

    if __name__ == "__main__": print currency(3458905.54) print currency(-49786002.40)

  2. 2. At 10:57 p.m. on 5 nov 2007, Tim Keating said:

    Using locale. FYI, the reason using locale didn't work is probably because you didn't set the locale first:

    >>> locale.setlocale(locale.LC_ALL, "")
'English_United States.1252'
>>> locale.format('%d', 12345, True)
'12,345'

    Counterintuitive, not well documented, non-Pythonic and just plain sucky, but there you go.

  3. 3. At 10:59 a.m. on 7 nov 2008, Tim Ruddick said:

    Reverse the digits, add commas after each group of three (except the last), then reverse the result.

    Nice and simple, but only works for integers; split on '\.' and rejoin if you have a decimal point.

    import re
def thous(x):
    return re.sub(r'(\d{3})(?=\d)', r'\1,', str(x)[::-1])[::-1]
  4. 4. At 5:19 p.m. on 2 mar 2009, Luciano Ramalho said:

    Here is a solution that does not use a regex:

    def splitthousands(s, sep=','):  
    if len(s) <= 3: return s  
    return splitthousands(s[:-3], sep) + sep + s[-3:]
  5. 5. At 7:55 a.m. on 10 nov 2009, Alexander Whiting said:

    Neat Luciano. So a full version for 2 decimal place numbers would be:

    def splitthousands(s, sep=','):
    sign='' rhs='' if s[0]=='-': sign='-' s=s[1:] if s.rfind('.')>0: rhs=s[-3:] s=s[:-3] if len(s) <= 3: return sign+s+rhs return sign+splitthousands(s[:-3], sep) + sep + s[-3:]+rhs

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