Récemment au boulot j'ai eu besoin d'éditer des configurations debian/ubuntu réseau.

Si dessous, un parser et un générateur, utilisable nativement via Fabric ou avec quelques modifications mineures nativement en python

from fabric.operations import put, sudo, local, run
import os.path
import re

def parse_debconf_network():
    """ Parse /etc/network/interfaces
    return a dictionnary of all elements
    """
    iface = {}
    output = run('cat /etc/network/interfaces')
    for line in output.split('/n'):
        if re.match(r'^(manual|auto)', line.strip()):
            ifacenum = re.split('/s+', line.strip())[1]
            ifacemode = re.split('/s+', line.strip())[0]
            iface[ifacenum] = {'ifacemode': ifacemode}
        elif not re.match(r'^#', line.strip()):
            key = re.split('/s+', line.strip())[0]
            if re.match(r'pre|post', key):
                if not iface[ifacenum].get(key, False):
                    iface[ifacenum][key] = []
                iface[ifacenum][key].append(' '.join(re.split('/s+', line.strip())[1:]))

            elif key != '':
                value = ' '.join(re.split('/s+', line.strip())[1:])
                iface[ifacenum][key] = value
    return iface


def generate_debconf_network(iface, remote_file='/etc/network/interfaces.new'):
    """ Generate a debian like network configuration file from a dictionnary (generated by parse_debconf_network)
    @param iface: The dictionnary
    @param remote_file: Output file
    """
    local_file = '/var/tmp/interfaces'
    f = open(local_file, 'w+')

    for cur_if, conf in iter(sorted(iface.iteritems())):
        f.write(conf['ifacemode'] + ' ' + cur_if + '/n')
        f.write('iface ' + conf['iface'] + '/n')
        for key, elem in iter(sorted(conf.iteritems())):
            if key != 'iface' and key != 'ifacemode':
                if type(elem) == list:
                    for subelem in elem:
                        f.write('/t' + key + ' ' + subelem + '/n')
                else:
                    f.write('/t' + key + ' ' + elem + '/n')

        f.write('/n')

    f.close()
    put(local_file, remote_file, use_sudo=True)
    sudo('chown root.root ' + remote_file)
    local('rm ' + local_file)

Et un petit guide de comment l'utiliser :

@task
def toto():
    myconf = parse_debconf_network()
    # On modifie le netmask d'eth0
    myconf['eth0']['netmask'] = '255.255.254.0'
    # On ajoute une route sur eth1
    myconf['eth1']['post-up'].append('ip route add 192.168.229.0/24 via 192.168.131.1 || true')
    myconf['eth1']['pre-down'].append('ip route del 192.168.229.0/24 via 192.168.131.1 || true')
    generate_debconf_network(myconf)