nio.py

#!/usr/bin/python
# -*- coding: utf-8 -*-

from os import listdir
import json

net = '/sys/class/net'
stat = net + '/{}/statistics/{}x_bytes'

interfaces = filter(lambda x: 'eth' in x, listdir(net))
data = {}

for interface in interfaces:
    received = open(stat.format(interface, 'r'), 'r').read().rstrip('\n')
    send = open(stat.format(interface, 't'), 'r').read().rstrip('\n')
    data[interface] = {
        'received': received,
        'send': send
    }

print json.dumps(data, sort_keys=True, indent=2, separators=(',', ': '))