from time import time
import urllib.request
import urllib.parse
import hashlib
import hmac

APIkey = b'provert-key'
secret = b'ceeeecret'
url = 'https://poloniex.com/tradingApi'

payload = {
    'command': 'returnBalances',
    'nonce': int(time() * 1000),
}

paybytes = urllib.parse.urlencode(payload).encode('utf8')
print(paybytes)

sign = hmac.new(secret, paybytes, hashlib.sha512).hexdigest()
print(sign)

headers = {
        'Key': APIkey,
        'Sign': sign,
}

req = urllib.request.Request(url, headers=headers, data=paybytes)
with urllib.request.urlopen(req) as response:
        the_page = response.read()
        print(the_page)