Requests for Poloniex API - python-3.x

Question

I trying work with Poloniex API. And I try get balances via Trading API methods. And I try do it with requests library like this:
import requests
import hmac
import hashlib
import time
import urllib
def setPrivateCommand(self):
poloniex_data = {'command': 'returnBalances', 'nonce': int(time.time() * 1000)}
post_data = urllib.parse.urlencode(poloniex_data).encode()
sig = hmac.new(str.encode(app.config['HMAC_KEYS']['Poloniex_Secret']), post_data, hashlib.sha512).hexdigest()
headers = {'Sign': sig, 'Key': app.config['HMAC_KEYS']['Poloniex_APIKey']}
polo_request = requests.post('https://poloniex.com/tradingApi', data=post_data, headers=headers, timeout=20)
polo_request = polo_request.json()
print('Request: {0}'.format(polo_request))
return polo_request
With this code I always get error with message: "Request: {'error': 'Invalid command.'}". What I do wrong?
From other side code below returns data without any problem! Look at this, please:
import requests
import hmac
import hashlib
import json
import time
import urllib
def setPrivateCommand(self):
poloniex_data = {'command': 'returnBalances', 'nonce': int(time.time() * 1000)}
post_data = urllib.parse.urlencode(poloniex_data).encode()
sig = hmac.new(str.encode(app.config['HMAC_KEYS']['Poloniex_Secret']), post_data, hashlib.sha512).hexdigest()
headers = {'Sign': sig, 'Key': app.config['HMAC_KEYS']['Poloniex_APIKey']}
req = urllib.request.Request('https://poloniex.com/tradingApi', data=post_data, headers=headers)
res = urllib.request.urlopen(req, timeout=20)
Ret_data = json.loads(res.read().decode('utf-8'))
print('Request: {0}'.format(Ret_data))
return Ret_data
I using Python 3.6

Answer 1

It's best to let requests handle post data because it creates the appropriate headers. Other than that i don't see anything wrong with your code.
def setPrivateCommand(self):
poloniex_data = {'command': 'returnBalances', 'nonce': int(time.time() * 1000)}
post_data = urllib.parse.urlencode(poloniex_data).encode()
sig = hmac.new(
str.encode(app.config['HMAC_KEYS']['Poloniex_Secret']), post_data, hashlib.sha512
).hexdigest()
headers = {'Sign': sig, 'Key': app.config['HMAC_KEYS']['Poloniex_APIKey']}
polo_request = requests.post(
'https://poloniex.com/tradingApi', data=poloniex_data, headers=headers, timeout=20
)
polo_request = polo_request.json()
print('Request: {0}'.format(polo_request))
return polo_request
Or you could specify the 'Content-Type' in headers if you want to have a string in data, example,
headers = {
'Sign': sig, 'Key': app.config['HMAC_KEYS']['Poloniex_APIKey'],
'Content-Type': 'application/x-www-form-urlencoded'
}
polo_request = requests.post(
'http://httpbin.org/anything', data=post_data, headers=headers, timeout=20
)