def _to_xml(number):
    """
    convert Python number to XML String representation

    Keyword Parameters:
    number  -- Python numeric variable

    >>> _to_xml(0)
    '0'
    >>> _to_xml(0.09834894752)
    '0.09834894752'
    >>> _to_xml(None)
    ''
    """
    if number is None:
        return ''
    return str(number)