# Global helper functions
def truncate(n, decimals=2):
    """Truncate a float to a particular number of decimals."""
    assert decimals > 0 and decimals < 10, "Decimals is weird"
    multiplier = 10 ** decimals
    return int(n * multiplier) / multiplier

def format_money(number):
    """Format a monetary amount with a $ and comma thousands separators."""
    return ("${:,}".format(truncate(number)))

def format_rate(rate):
    """Format a multiplier nee rate to look nice."""
    if rate >= 1.0:
        return format_rate(rate - 1.0)
    else:
        return "{:<}%".format(round(rate * 100, 3))