#!/usr/bin/env python
import subprocess
import json

def format_bytes(size):
    # 2**10 = 1024
    power = 2**10
    n = 0
    power_labels = {0 : '', 1: 'K', 2: 'M', 3: 'G', 4: 'T'}
    while size > power:
        size /= power
        n += 1
    return size, power_labels[n]+'B'

output = subprocess.getstatusoutput("vnstat -tr 2 --json -i en0")

result = json.loads(output[1])
rxb = result['rx']['bytespersecond']
txb = result['tx']['bytespersecond']

formatted_rx = format_bytes(rxb)
formatted_tx = format_bytes(txb)

rx = round(formatted_rx[0], 2)
tx = round(formatted_tx[0], 2)

print("{}{}/s {}{}/s".format(rx, formatted_rx[1], tx, formatted_tx[1]))