gistfile1.py

    def add_iface_to_netns(if_name, ns_name):
        #
        # IPDB instantiation, as well as NetNS instantiation,
        # are expensive operations. NetNS spawns an additional
        # process, and IPDB populates itself with all the data
        # from the operating system networking.
        #
        # Maybe, it would be not a bad idea to keep IPDB as a
        # long-running global object, or like that.
        #
        ipdb = IPDB()
        try:
            # here you open NetNS
            netns = NetNS(ns_name)
            iface = getattr(ipdb.interfaces, if_name)
            # here the exception can be raised
            with iface as veth:
                veth.net_ns_fd = netns.netns
            ##
            # in the case of an exception, this code is not called
            #
            netns.close()
            #
            # not closed netns will cause all the script to hang on exit
            ##
        except Exception as e:
            print(e)
        finally:
            print("Release...")
            ipdb.release()