Reading data from a text file in Python according to the parameters provided

Question

I have a text file something like this

Mqtt_allowed=true
Mqtt_host=192.168.0.1
Mqtt_port=2223
<=============>
cloud_allowed=true
cloud_host=m12.abc.com
cloud_port=1232
<=============>
local_storage=true
local_path=abcd

I needed to get each of the value w.r.t parameter provided by the user. What i am doing right now is:

def search(param):
    try:
        with open('config.txt') as configuration:
            for line in configuration:
                if not line:
                    continue    
                function, f_input=line.split("=")
                if function == param:
                    result=f_input.split()
                    break
                else:
                    result="0"
    except FileNotFoundError:
        print("File not found: ")
    return result

mqttIsAllowed=search("Mqtt_allowed")
print mqttIsAllowed

Now when i call only mqt stuff it is working fine but when i call cloud or anything after the "<==========>" separation it throws an error. Thanks

Answer 1

Because you are trying to split on the = character in a style that seems to be standard INI format, it is safe to assume that your pairs will be at max size 2. I'm not a fan of using methods that rely on character checking (unless specifically called for), so give this a whirl:

def search(param):
    result = '0' # declare here
    try:
        with open('config.txt') as configuration:
            for line in configuration:
                if not line:
                    continue  

                f_pair = line.strip().split("=") # remove \r\n, \n

                if len(f_pair) > 2: # your separator will be much longer
                    continue
                else if f_pair[0] == param:
                    result = f_pair[1]
                    # result = f_input.split() # why the 'split()' here?
                    break

    except FileNotFoundError:
        print("File not found: ")

    return result

mqttIsAllowed=search("Mqtt_allowed")

I'm pretty sure the error you were getting was a ValueError: too many values to unpack.

Here is how I know that:

When you call this function for any of the Mqtt_* values, the loop never encounters the separator string <=============>. As soo as you try to call anything below that first separator (for example a cloud_* key), the loop eventually reaches the first separator and tries to execute:

function, f_input = line.split('=')

But that wont work, in fact it will tell you:

ValueError: too many values to unpack (expected 2)

And that is because you are forcing the split() call to push into only 2 variables, but a split('=') on your separator string will return a list of 15 elements (a '<', a '>' and 13 ''). Thus, doing what I have posted above ensures that your split('=') still goes off, but checks to see if you hit a separator or not.