import sys
#Take parameters of a plain text (file parameters.txt)

def get(rule_name,parameter_name):
    try:
        with open("parameters.txt", "r") as infile:
            for line in infile:
                frame = line.split(":")
                if line.startswith(rule_name.lower()) and frame[1] == parameter_name.lower():
                    return check_len(frame) #comprova longitud i retorna el valor
    except Exception: #No such file or directory si no se encentra el archivo
        raise NameError("Doesnt exist the .txt especified")


def check_len(frames):
    if len(frames) == 3:
        return frames[2]
    elif len(frames) < 3 or len(frames) > 3:
        raise Exception("Wrong format in parameter required")

if __name__=="__main__":
    try:
        print(get("metadata","THR1")) #Este seria el formato de la llamada
    except TypeError:
        raise Exception("Invalid get format, missing rule or parameter (or both)") #en caso de no pasar una regla o parametro o introducir parametros adicionales

metadata:thr1:1
metadata:thr2:2
metadata:thr3:3
metadata:thr4:4
metadata:thr5:5