Finding field widths of floats for neat printing

[Steven Taschuk]

Quoth Andrew Gregory:
> I want to write lists of floating point numbers to text files in neat
> columns with decimal points aligned, right-hand edges straight (rather
> than ragged), and without unnecessary trailing zeros, e.g.
> 1.1    -34.67     0.006  
> 2.0     -1.05     0.010  
> etc.
  [...]

How about this?

    def strparts(value):
        s = ('%f' % value).rstrip('0').split('.')
        if len(s) < 2:
            s.append('')
        return s

    def formatfor(values):
        leftparts, rightparts = zip(*map(strparts, values))
        leftwidth = max(map(len, leftparts))
        precision = max(map(len, rightparts))
        width = leftwidth + precision
        if precision:
            width += 1 # decimal point
        return '%%%d.%df' % (width, precision)

    table = [[1.1, -34.67, 0.006], [2, -1.05, 0.01]]
    formats = map(formatfor, zip(*table))
    for row in table:
        for fmt, val in zip(formats, row):
            print fmt % val,
        print

Output:

    1.1 -34.67 0.006
    2.0  -1.05 0.010

-- 
Steven Taschuk                                7\ 7'Z {&~         .
staschuk at telusplanet.net                        Y r          --/hG-
                                            (__/ )_             1^1`