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El Diego Efe
Asked: 2020-12-02 10:05:52 +0800 CST 2020-12-02 10:05:52 +0800 CST

Variable initialization in Python using a separate function from main()

  • 772

To initialize some variables in a Python program (in a structured way, without using OOP), I want to use a function called initialization() , which is called from a main() function . The problem is the scope of these variables, since if I give them their initial value in the initialization() function , trying to use them in the main() function will generate an error because they do not exist there. For example:

import serial

def inicializacion():
    puerto = '/dev/ttyACM0'
    baudRate = 115200
    buffer = ''
    ser = serial.Serial(puerto, baudRate, timeout=1)


def main():
    inicializacion()
    buffer = buffer + leerDatos(ser)

What alternatives are there to avoid using "global" in the initialization function? Is it possible to implement any solution without having to pass the variables as arguments and without having to return them on the "return"?

python

4 Answers

  1. Best Answer

    Well, I don't think this is possible without resorting to the non-recommended haute mantein global. The specific case you show applies perfectly in Object Oriented Programming, it would be good if you explain the reason why you are trying to avoid it:

    import serial


class Clase():
    def __init__(self, puerto, baud_rate, buffer) # inicializacion()
        self.puerto = puerto
        self.baud_rate = baud_rate
        self.buffer = buffer
        self.serial = serial.Serial(puerto, baudRate, timeout=1)

    def leer_datos(self):
        # Tu código

    If you are trying to use the configuration parameters, you could create a specific file which will be imported on demand:

    settings.py

    puerto = '/dev/ttyACM0'
baudRate = 115200
buffer = ''

    main.py

    import serial
import settings


def main():
    ser = serial.Serial(settings.puerto, settings.baudRate, timeout=1)
    buffer = settings.buffer + leerDatos(ser)

    Another option is the one mentioned by @Carlangueitor in which you move your configuration to a file .envwithin your project and thus avoid exposing the configuration in one of the files. You can use dotenv .

    • 11

  2. I think you could use a dictionary. You can pass the dictionary as well as return it, keeping the changes you make inside it. Take a look at the following code.

    def inicializacion():
    toret = {}
    toret["puerto"] = '/dev/ttyACM0'
    toret["baudRate"] = 115200
    toret["buffer"] = ''

    return toret


def main():
    datos = inicializacion()
    datos["buffer"] = "hola"
    print(datos["buffer"])
    print(datos)

main()

    You have the code here: http://ideone.com/BjQyuX I hope you find it useful.

    • 9

  3. The simplest and pythonic way, adapting your own code:

    import serial

def inicializacion(puerto='/dev/ttyACM0', baudRate=115200):
    ser = serial.Serial(puerto, baudRate, timeout=1)
    return ser


def main():
    ser = inicializacion()
    buffer=''
    buffer = buffer + leerDatos(ser)

    # El puerto se ha de cerrar para evitar fugas de memoria..
    ser.close()

    The ideal would be to change the name of inicializacionto a more expressive and explicit name, such as:inicializacion_puerto_serie

    By passing the values ​​to the function inicializacionas default parameters, you can reuse the code with another or baud_ratedifferent port.

    Never forget when you open a file or a serial port (which for the system is the same) to close it correctly to avoid memory leaks.

    • 4

  4. I propose the following:

    import serial

puerto='/dev/ttyACM0'
baudRate=115200

def main():
    buffer=''
    serial.Serial(puerto, baudRate, timeout=1)
    buffer=buffer+leerDatos(str)
    • 3