diff --git a/freqtrade/tests/testdata/download_backtest_data.py b/freqtrade/tests/testdata/download_backtest_data.py
index 463087588..6aef5f9f0 100644
--- a/freqtrade/tests/testdata/download_backtest_data.py
+++ b/freqtrade/tests/testdata/download_backtest_data.py
@@ -1,13 +1,16 @@
-#!/usr/bin/python3.6
+"""This module download automatically json data of crypto currencies in bittrex"""
+#!/usr/bin/env python3
 
 from urllib.request import urlopen
 
-currencies = ["ok","neo","dash","etc","eth","snt"]
+CURRENCIES = ["ok", "neo", "dash", "etc", "eth", "snt"]
 
-for cur in currencies:
-	url = 'https://bittrex.com/Api/v2.0/pub/market/GetTicks?marketName=BTC-'+cur+'&tickInterval=fiveMin'
+for cur in CURRENCIES:
+	url1 = 'https://bittrex.com/Api/v2.0/pub/market/GetTicks?marketName=BTC-'
+	url2 = '&tickInterval=fiveMin'
+	url = url1+cur+url2
 	x = urlopen(url)
-	data = x.read()
-	str2 = str(data,'utf-8')
-	with open("btc-"+cur+".json", "w") as fichier:
-		fichier.write(str2)
+	json_data = x.read()
+	json_str = str(json_data, 'utf-8')
+	with open("btc-"+cur+".json", "w") as file:
+		file.write(json_str)