format_metric.py

import re

FS_RE = "{([GMkp]{0,1})(:)([\.,]{0,1})([0-9]*)([dfg]{1})}(.*)$"
def format_metric(format_str, value):
    """
    Format a report metric (attribute or table column value) according to our
    in-house rules.  These resemble Python format strings (plus optional
    suffix), but with the addition of optional scaling flags.
    """
    if value is None:
        return "NA"
    elif format_str is None:
        return str(value)
    else:
        m = re.match(FS_RE, format_str)
        if m is None:
            raise ValueError("Format string '{s}' is uninterpretable".format(
                             s=format_str))
        if m.groups()[0] == 'p':
            value *= 100.0
        elif m.groups()[0] == 'G':
            value /= 1000000000.0
        elif m.groups()[0] == 'M':
            value /= 1000000.0
        elif m.groups()[0] == 'k':
            value /= 1000.0
        if isinstance(value, float) and m.groups()[4] == 'd':
            value = int(value)
        fs_python = "{{:{:s}{:s}{:s}}}".format(*(m.groups()[2:5]))
        formatted = fs_python.format(value)
        # the percent symbol can be implicit
        if m.groups()[0] == 'p' and m.groups()[-1] == '':
            return formatted + "%"
        else:
            return formatted + m.groups()[-1]