Format a number with '%g'-like format, except that

        a) the length of the output string will be the requested length.
        b) positive numbers will have a leading blank.
        b) the precision will be as high as possible.
        c) trailing zeros will not be trimmed.

    The precision will typically be length-7.

    Arguments
    ---------
    val       value to be formatted
    length    length of output string

    Returns
    -------
    string of specified length.

    Notes
    ------
     Positive values will have leading blank.

def gformat(val, length=11):
    """Format a number with '%g'-like format, except that

        a) the length of the output string will be the requested length.
        b) positive numbers will have a leading blank.
        b) the precision will be as high as possible.
        c) trailing zeros will not be trimmed.

    The precision will typically be length-7.

    Arguments
    ---------
    val       value to be formatted
    length    length of output string

    Returns
    -------
    string of specified length.

    Notes
    ------
     Positive values will have leading blank.

    """
    try:
        expon = int(log10(abs(val)))
    except (OverflowError, ValueError):
        expon = 0
    length = max(length, 7)
    form = 'e'
    prec = length - 7
    if abs(expon) > 99:
        prec -= 1
    elif ((expon > 0 and expon < (prec+4)) or
          (expon <= 0 and -expon < (prec-1))):
        form = 'f'
        prec += 4
        if expon > 0:
            prec -= expon
    fmt = '{0: %i.%i%s}' % (length, prec, form)
    return fmt.format(val)