import requests


def lookup(tracking_code):
    """
    Receives the tracking code as string and does online search.
    Returns the html received from the page lookup
    """
    params = 'Z_ACTION=Search&P_TIPO=001&P_LINGUA=001&P_COD_UNI={}'.format(tracking_code)
    url = 'http://websro.correios.com.br/sro_bin/txect01$.QueryList'
    return requests.post(url, params, timeout=10).text