Python range filter - allows quick retrieval of keys within a given range

rangefilter.py

from blist import sorteddict, blist

class RangeFilter(sorteddict):
    def filter_items(self, lt=None, lte=None, gt=None, gte=None):
        """Return the items with keys corresponding to the supplied parameters
        
        ('lt' denotes 'less than', 'gte' denotes 'greater than or equal' etc)
        """
        bottom, top = self._get_range_indexes(lt, lte, gt, gte)
        return self.items()[bottom:top]
    
    def filter_values(self, lt=None, lte=None, gt=None, gte=None):
        """Return the values with keys corresponding to the supplied parameters
        
        ('lt' denotes 'less than', 'gte' denotes 'greater than or equal' etc)
        """
        bottom, top = self._get_range_indexes(lt, lte, gt, gte)
        return self.values()[bottom:top]
        
    def filter_keys(self, lt=None, lte=None, gt=None, gte=None):
        """Return the keys corresponding to the supplied parameters
        
        ('lt' denotes 'less than', 'gte' denotes 'greater than or equal' etc)
        """
        bottom, top = self._get_range_indexes(lt, lte, gt, gte)
        return self.keys()[bottom:top]
    
    def _get_range_indexes(self, lt=None, lte=None, gt=None, gte=None):
        bottom = 0
        keys = self.keys()
        top = len(keys) - 1
        if gte is not None:
            bottom = keys.bisect_left(gte)
        if gt is not None:
            bottom = keys.bisect_right(gt)
        if lte is not None:
            top = keys.bisect_right(lte)
        if lt is not None:
            top = keys.bisect_left(lt)
        return bottom, top