expression.py 文件源码

def validate_expression(expr_string):
    """
    Validate the provided expression string.
    :type expr_string: str
    :param expr_string: Expression string to validate.
    :returns: Returns a handle that can be use to validate
              name usage against an environment.
    :raises: exception.BananaInvalidExpression
    """
    if not isinstance(expr_string, basestring):
        raise exception.BananaArgumentTypeError(
            expected_type=basestring,
            received_type=type(expr_string)
        )
    parser = ExpressionParser()
    try:
        res = parser.parse_tree(expr_string)
        return ExpressionHandle(res, expr_string)
    except p.ParseException as e:
        raise exception.BananaInvalidExpression(str(e))