"""
Various specialized string display formatting utilities
"""

def commas(N):
    """
    format positive integer-like N for display with
    commas between digit groupings: xxx,yyy,zzz
    """
    digits = str(N)
    assert(digits.isdigit())
    result = ''
    while digits:
        digits, last3 = digits[:-3], digits[-3:]
        result = (last3 + ',' + result) if result else last3
    return result

def money(N, width=0):
    """
    format number N for display with commas, 2 decimal digits,
    leading $ and sign, and optional padding: $  -xxx,yyy.zz
    """
    sign   = '-' if N < 0 else ''
    N      = abs(N)
    whole  = commas(int(N))
    fract  = ('%.2f' % N)[-2:]
    format = '%s%s.%s' % (sign, whole, fract)
    return '$%*s' % (width, format) 

if __name__ == '__main__':
    tests  = 0, 1        # fails: -1, 1.23
    tests += 12, 123, 1234, 12345, 123456, 1234567
    tests += 2 ** 32, 2 ** 100
    for test in tests:
        print commas(test)
    
    print
    tests  = 0, 1, -1, 1.23, 1., 1.2, 3.14159
    tests += 12.34, 12.344, 12.345, 12.346
    tests += 2 ** 32, (2 ** 32 + .2345)
    tests += 1.2345, 1.2, 0.2345
    tests += -1.2345, -1.2, -0.2345
    tests += -(2 ** 32), -(2**32 + .2345)
    tests += (2 ** 100), -(2 ** 100)
    for test in tests:
        print money(test, 17)