SerialButton Python

#!/usr/bin/python

import serial
import serial.tools.list_ports
import subprocess
import os, random

ser = None

filesDir = "/home/missiriss/Изображения"
lastFile = ""

def open_port():
    global ser
    ports = list(serial.tools.list_ports.comports())
    if(len(ports) > 0):
        try:
            ser = serial.Serial(ports[0].device)
        except:
            ser = None
            return False
        return True
    else:
        ser = None
        return False

def wait_command():
    global ser
    while ser is None:
        open_port()
    try:
        response = ser.readline()
    except :
        ser = None
        return wait_command()
    return response.decode("utf-8")[0]

def random_file():
    global lastFile
    list = os.listdir(filesDir)
    if len(list) == 0:
        return ""
    if len(list) == 1:
        return list[0]
    file = random.choice(list)
    while file == lastFile:
        file = random.choice(os.listdir(filesDir))
    lastFile = file
    return file


while True:
    cmd = wait_command()
    if(cmd == '1'):
        subprocess.run(["echo", random_file()])
    elif(cmd == '2'):
        subprocess.run(["echo", "2" , "multy_args"])
    else:
        print('XZ')