def login() :
    # login
    session = requests.session()
    payload = {'username': 'xxxxxx', 'password': 'yyyyyy'}
    login=session.post("https://piwigo_url/ws.php?format=rest&method=pwg.session.login", data=payload)
    print("TEST login=", login)
    return session

def add_tags(tag_list, session) :
    res = []
    url = "https://piwigo_url/ws.php?format=rest&method=pwg.tags.add&name="
    for tag in tag_list :
        payload = {'name': tag}
        r=session.post("https://empiredesloutres.fr/photos/ws.php?format=rest&method=pwg.tags.add", data=payload)
        print("TEST r =", r)
        res += [(tag.lower(), browser.parsed.find("id").text)]
    return res

session = login()
add_tags(["test"],session)