def _match_overlay(self, raster, overlay_spec):
        """
        Given a raster or input overlay, generate a list of matched
        elements (None if no match) and corresponding tuple of match
        strength values.
        """
        ordering = [None]*len(overlay_spec) # Elements to overlay
        strengths = [0]*len(overlay_spec)   # Match strengths

        elements = raster.values() if isinstance(raster, Overlay) else [raster]

        for el in elements:
            for pos in range(len(overlay_spec)):
                strength = self._match(el, overlay_spec[pos])
                if strength is None:               continue  # No match
                elif (strength <= strengths[pos]): continue  # Weaker match
                else:                                        # Stronger match
                    ordering[pos] = el
                    strengths[pos] = strength
        return ordering, strengths
def _match_overlay ( self , raster , overlay_spec ) : ordering = [ None ] * len ( overlay_spec ) strengths = [ 0 ] * len ( overlay_spec ) elements = raster . values ( ) if isinstance ( raster , Overlay ) else [ raster ] for el in elements : for pos in range ( len ( overlay_spec ) ) : strength = self . _match ( el , overlay_spec [ pos ] ) if strength is None : continue elif ( strength <= strengths [ pos ] ) : continue else : ordering [ pos ] = el strengths [ pos ] = strength return ordering , strengths
Given a raster or input overlay, generate a list of matched
        elements (None if no match) and corresponding tuple of match
        strength values.