root/trac/hacks/marketplugin/0.9/tracmarket/util.py

def XXXroundp(self, f):
    '''round off price f to basket_price/100 precision'''
    precision = math.log10(self.basket_price/100) * -1
    return round(f, precision)
        
# Price and Size need to be the same internal precision, because
# ledger transactions don't make a distinction between price or size
# types, but orders do; we'd have a reconcilation mess
class RoundedFloat(float):
        
    def __new__(cls, f):
        '''convert to float and round off price f to 1/1000 precision'''
        if f is None:
            return None
        val = round(float(f), 3)
        self = float.__new__(cls, val)
        return self

class Price(RoundedFloat):

    def __str__(self):
        return "%.2f" % self

class Size(RoundedFloat):
        
    def __str__(self):
        return "%.1f" % self