import types


def joinCSVFields(fields):
    """
    Returns a CSV record (eg a string) from a sequence of fields.
    Fields containing commands (,) or double quotes (") are quoted
    and double quotes are escaped (""). The terminating newline is
    NOT included.
    """
    newFields = []
    for field in fields:
        assert type(field) is types.StringType
        if field.find('"') != -1:
            newField = '"' + field.replace('"', '""') + '"'
        elif field.find(',') != -1 or field.find('\n') != -1 or field.find('\r') != -1:
            newField = '"' + field + '"'
        else:
            newField = field
        newFields.append(newField)
    return ','.join(newFields)