crypto tracker that rings a bell when desired change has happened in price

coincap_cryptotracker.py

"""
crypto tracker that rings a bell when desired change has happened in price
using coincap.io
spported assets: bitcoin, ethereum and more
"""

import http.client
import json
import sys
import time

COINCAP_API_HOST = 'api.coincap.io'
COINCAP_API_GET_ASSETS = '/v2/assets?ids={0}'
COINCAP_API_GET_ASSET_BY_ID = '/v2/assets/{0}'

SUPPORTED_IDS = ['bitcoin', 'ethereum']
ASSETS = {}

for aid in SUPPORTED_IDS:
    ASSETS[aid] = {}

def get_all_assets():
    conn = http.client.HTTPSConnection(COINCAP_API_HOST)
    conn.request('GET', COINCAP_API_GET_ASSETS.format(','.join(SUPPORTED_IDS)))
    response = conn.getresponse()
    if response.status == 200:
        data = json.loads(response.read())
        for a in data.get('data'):
            if a.get('id') in SUPPORTED_IDS:
                ASSETS[a.get('id')] = a
    conn.close()

def ring_bell():
    sys.stdout.write('\a')
    sys.stdout.flush()

def get_asset(asset):
    conn = http.client.HTTPSConnection(COINCAP_API_HOST)
    conn.request('GET', COINCAP_API_GET_ASSET_BY_ID.format(asset))
    response = conn.getresponse()
    data = None
    if response.status == 200:
        data = json.loads(response.read()).get('data')
    conn.close()
    return data

def track(asset, change):
    data = None
    while True:
        try:
            cur_data = get_asset(asset)
            if not data:
                data = cur_data
            if not cur_data == None:
                cur_price = float(cur_data.get('priceUsd'))
                old_price = float(data.get('priceUsd'))
                diff = ((cur_price - old_price) / old_price) * 100
                if change > 0 and change <= diff:
                    ring_bell()
                elif change < 0 and change >= diff:
                    ring_bell()
            print("{0} : changed {1} % : prev_price {2} : cur_price {3}".format(asset, diff, old_price, cur_price))
        except:
            pass
        
        time.sleep(600)


def usage():
    print('[program] [asset] [change]')

if __name__ == "__main__":

    if len(sys.argv) != 3:
        usage()
        sys.exit()

    try:
        asset = str(sys.argv[1])
        change = float(sys.argv[2])
    except:
        usage()
        sys.exit()

    if not asset in SUPPORTED_IDS:
        print('Supported Assets : {0}'.format(SUPPORTED_IDS))
        sys.exit()

    track(asset, change)