def uniprot_ec(uniprot_id):
    """Retrieve the EC number annotation for a UniProt ID.

    Args:
        uniprot_id: Valid UniProt ID

    Returns:

    """
    r = requests.post('http://www.uniprot.org/uniprot/?query=%s&columns=ec&format=tab' % uniprot_id)
    ec = r.content.decode('utf-8').splitlines()[1]

    if len(ec) == 0:
        ec = None

    return ec
Retrieve the EC number annotation for a UniProt ID.

    Args:
        uniprot_id: Valid UniProt ID

    Returns: