It has a simple API and it is fast and easy to use. It also works across multiple CPU/cores for extra speed.
Here is an example that parses an OSM file and counts all ways that are tagged as a highway.
from imposm.parser import OSMParser # simple class that handles the parsed OSM data. class HighwayCounter(object): highways = 0 def ways(self, ways): # callback method for ways for osmid, tags, refs in ways: if 'highway' in tags: self.highways += 1 # instantiate counter and parser and start parsing counter = HighwayCounter() p = OSMParser(concurrency=4, ways_callback=counter.ways) p.parse('germany.osm.pbf') # done print counter.highways