quick hostname reversal

reversehostname.py

# This is very useful for sorting hostnames. 
def revhost(host):
    """ split a hostname into segments, reverse them, and then rejoin them """
    segments = host.split('.')
    segments.reverse()
    reversed = ".".join(segments)
    return reversed

domain = 'a.ns.example.com'
rdomain = revhost(domain)
print domain, rdomain
# a.ns.example.com com.example.ns.a
ndomain = revhost(rdomain)
print domain, ndomain
# a.ns.example.com a.ns.example.com