Python local variable 'message' referenced before assignment problem-CodePudding

liquid = [l_press,l_dosage,l_bottle,l_position,l_clog,l_counter]
for j in range(len(liquid)):
        data = liquid_filling(liquid[j])
        publish.single(liquid[j],data,qos = 0, hostname = hostname,port=2259)

def liquid_filling(topic):
    if topic == "Liquid_filling/pressure":
        message = random.uniform(4.0,5.0)
    elif topic == "Liquid_filling/dosage":
        message = random.uniform(495.0,505.0)
    elif topic == "Liquid_filling/bottle_presence" or topic== "Liquid_filling/position" or topic=="Caps/position":
        if i % 2 == 0:
           message = 'YES'
        else:
           message = 'NO'
    elif topic == "Liquid_filling/counter":
        message = i
    return message

I receive the following error:

Error: local variable 'message' referenced before assignment

I think that it must be something related with the alignment of the code but I have double-check it and I can't find any problem. Also, the variable message is only used to return a value.

I have already checked other related questions in this forum and I still cannot find the answer.

I would appreciate your help.

CodePudding user response：

In your case this is happening because for some reason the topic is not passing in your if conditions.

As there is no else, automatically when it does not pass the conditions you will not have message defined, causing it to not find for the return.

Make a new check of the value sent for analysis of conditions or to test that it did not pass any of the conditions, add:

else:
    message = 'not pass conditions'

And you will receive this (not pass conditions) value as a return, proving that it did not pass the conditions.

In short: you are looking for the problem in the wrong place in your code.

CodePudding user response：

I solved it. It was that I had a topic named "Caps/position" and it should be named "Liquid_filling/position".

The code that works is as follows:

def liquid_filling(topic):
    if topic == "Liquid_filling/pressure":
        message = random.uniform(4.0,5.0)
    elif topic == "Liquid_filling/dosage":
        message = random.uniform(495.0,505.0)
    elif topic == "Liquid_filling/bottle_presence" or topic== "Liquid_filling/position" or topic=="Liquid_filling/anti_clogging":
        if i % 2 == 0:
           message = 'YES'
        else:
           message = 'NO'
    elif topic == "Liquid_filling/counter":
        message = i
    else: 
        message = 'There is an error'
    return message

Thanks for your comments because I was able to realize the problem!