<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_apcor(expnum, ccd, version='p', prefix=None):
 """ retrieve the aperture correction for this exposure @param expnum: @param ccd: @param version: @param prefix: @return: """

    uri = get_uri(expnum, ccd, ext=APCOR_EXT, version=version, prefix=prefix)
    apcor_file_name = tempfile.NamedTemporaryFile()
    client.copy(uri, apcor_file_name.name)
    apcor_file_name.seek(0)
    return [float(x) for x in apcor_file_name.readline().split()]