python3 - check if return is not None

Is it efficient to do this in python3?

if request_link(requested_domain, requested_link) is not None
    domain_res, link_res, r_res = request_link(requested_domain, requested_link)
    parse_results(domain_res, r_res)

Does this mean that interpreter will look into the same function twice?

Is it efficient? If not, what is the better way to check if the function returns none and act upon the result?

thank you!