OSM Parsing: Python vs. Obj-C

from lxml import etree


OSM_API_URL = "http://api.openstreetmap.org/api/0.6/map?bbox=%s"


def get_streets(bbox):
    """
    Makes an OSM API request and parses the streets and their waypoints in the
    XML response, returns a list
    """
    tree = etree.parse(OSM_API_URL % bbox)
    streets = []

    for way in tree.xpath("//way"):
        waypoints = []

        for node in way.getchildren():

            if node.tag == "nd":
                point = tree.xpath("//node[@id=%s]" % node.attrib.get("ref"))[0]

                waypoints.append((point.attrib.get("lat"), point.attrib.get("lon")))

        streets.append(waypoints)

    return streets






NSArray *PerformWayQuery(NSData *document) {
	xmlDocPtr doc;
	
	doc = xmlReadMemory([document bytes], [document length], "", NULL, XML_PARSE_RECOVER);
	
    if (doc == NULL) {
		NSLog(@"Unable to parse.");
		return nil;
    }
	
	NSMutableArray *ways = [[NSMutableArray alloc] init];
	NSArray *waysList = PerformXPathQuery(doc, @"//way");
	
	int count = 0;
	
	for (NSDictionary *way in waysList) {
		if (count > 50) {
			break;
		}
		
		NSMutableArray *coordinates = [[NSMutableArray alloc] init];
		
		for (NSDictionary *node in [way objectForKey:@"nodeChildArray"]) {
			if ([[node objectForKey:@"nodeName"] isEqualToString:@"nd"]) {
				NSArray *nodeCoordinates = PerformXPathQuery(doc, [NSString stringWithFormat:@"//node[@id=%@]", [[[node objectForKey:@"nodeAttributeArray"] objectAtIndex:0] objectForKey:@"nodeContent"]]);
				CLLocationCoordinate2D coordinate;
				
				for (NSDictionary *attribute in [[nodeCoordinates objectAtIndex:0] objectForKey:@"nodeAttributeArray"]) {
					if ([[attribute objectForKey:@"attributeName"] isEqualToString:@"lat"]) {
						coordinate.latitude = [[attribute objectForKey:@"nodeContent"] doubleValue];
					} else if ([[attribute objectForKey:@"attributeName"] isEqualToString:@"lon"]) {
						coordinate.longitude = [[attribute objectForKey:@"nodeContent"] doubleValue];
					}
				}
				
				CLLocation *location = [[CLLocation alloc] initWithLatitude:coordinate.latitude longitude:coordinate.longitude];
				
				[coordinates addObject:location];
				[location release];
			}
		}
		
		Street *street = [[Street alloc] initWithDictionary:[NSDictionary dictionaryWithObject:coordinates forKey:@"coordinates"]];
		
		[ways addObject:street];
		
		[street release];
		[coordinates release];
		
		count++;
	}
	
    xmlFreeDoc(doc); 
	
	return ways;
}