Extract ipv6 prefix in python

Question

Given either the binary or string representation of an IPv6 address and its prefix length, what's the best way to extract the prefix in Python?

Is there a library that would do this for me, or would I have to:

1. convert the address from string to an int (inet_ntop)
2. Mask out the prefix
3. Convert prefix back to binary
4. Convert binary to string (inet_ntop)

Answer 1

See http://code.google.com/p/ipaddr-py/

With this, you can do

py> p=ipaddr.IPv6("2001:888:2000:d::a2")
py> p.SetPrefix(64)
py> p
IPv6('2001:888:2000:d::a2/64')
py> p.network_ext
'2001:888:2000:d::'

etc.