Python How can I make this Python script add a limit to trades made with API?

Code
import requests

import urllib.request

import urllib.parse

import http.client

import hashlib

import hmac

import time

import json

from urllib.request import urlopen



The_Currency_Pair = input('Which Currency Pair?\nPAIRS TO CHOOSE FROM:\nUSDT_BTC\nUSDT_XRP\nUSDT_ETH\nUSDT_BCH\nUSDT_STR\nUSDT_LTC\nUSDT_ETC\nUSDT_XMR\n')





api = 'poloniex.com/tradingApi'

key = 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'

secret = 'XXXXXXXXXXXXXXXXXXXXXXXXX'





def main():

    poloniexPrices = urlopen('poloniex.com/public?command=returnTicker').read()

    poloniexjson = json.loads(poloniexPrices)

    poloniexlastP = poloniexjson[The_Currency_Pair]['last']





    poloniexOCHL = urlopen('poloniex.com/public?command=returnChartData&currencyPair=USDT_BCH&start=1538352000&period=86400').read()

    poloniexOCHLjson = json.loads(poloniexOCHL)

    poloniexlasthigh = poloniexOCHLjson[-2]['high']





    print ('Last Price')

    print (poloniexlastP)

    print ('----------------------------------------')

    print ('Last Day High')

    print (poloniexlasthigh)

    print ('----------------------------------------')







    data = {

        'command': 'returnBalances',

        'nonce'  : int(time.time() * 1000)

    }

    data = urllib.parse.urlencode(data).encode()



    signature = hmac.new(secret.encode(), data, hashlib.sha512)



    headers = {

        'Key' : key,

        'Sign': signature.hexdigest()

    }



    request = urllib.request.Request(

        url=api, data=data, headers=headers, method='POST'

    )



    text = urllib.request.urlopen(request).read().decode()



    print ('MY ACCOUNT BALANCE')

    try:

        print(json.loads(text)['USDT'])

    except:

        print(text)

    print ('-----------------------------------------')







    if float(poloniexlastP) > 0:

        print ('PLACING TRADE')

        print ('-----------------------------------------------')



        parms = {"command":"buy",

             "currencyPair":The_Currency_Pair,

             "rate":100,

             "immediateOrCancel":1,

             "amount":0.01,

             "nonce":int(time.time() * 1000)}



        parms = urllib.parse.urlencode(parms).encode()



        signature = hmac.new(secret.encode(), parms, hashlib.sha512)



        headers = {'Key' : key,

                   'Sign': signature.hexdigest()}



        request = urllib.request.Request(

        url=api, data=parms, headers=headers, method='POST')



        text = urllib.request.urlopen(request).read().decode()



        ordernumber = (json.loads(text)['orderNumber'])



        print ('Order Number:')

        print (ordernumber)









while True:

    main()

    time.sleep(60)