参数错误/异常

Question

我想知道如何抛出异常/错误来说明参数为null或不在字典中的.txt文件中的参数。

字典是这样的：

"""rule:parameter:value"""
aa:alfa:1
bba:beta:15

我现在知道了这个：

def get(rule_name,parameter_name):
    try:
        with open("parameters.txt", "r") as infile:   
            for line in infile:                 
                if line.startswith(rule_name.lower()) and line.split(":")[1] == parameter_name.lower():      
                    return line.split(":")[2]   
    except Value:
        print "Error"


if __name__=="__main__":
    print(get("aa","alfa")) #return the value associated to the rule and the parameter

Answer 1

只需引发值错误

raise ValueError("you parameter is null or in wrong format")