Are there normal global objects in python?

Question

Python

Prehistory: there is a pi on which the python script is running and waiting for data via serial when it receives a command to do something, for example, 2 necessary functions - turn on and off a certain track in omxplayer. Everything would be fine, but you need to make a smooth transition between tracks, and this is already missing in the player's functionality. I found a crutch solution in the form of a wrapper for this player, it creates an object of this type player=OMXPlayer(filename) which gives the player.play command, etc.
The script itself is built as a bunch of elif (command)
And the problem is that if you start the player in one of these if, then it is not visible from the other, the global parameter does not change anything, it says that there is no such object
the whole script revolves around while(true) of one def. I suspect that the problem is related to the fact that global objects are updated only after leaving the def, but not a fact. What can be done in this situation?
ps I myself spent only a couple of hours in python, so I don’t know a lot of
code in it

#!/usr/bin/python
import serial, time, os, sys
from omxplayer import OMXPlayer
ser = serial.Serial ()
try:
    ser = serial.Serial(
        port='/dev/ttyACM0',
        baudrate = 115200,
        timeout=1
    )
    print 'ttyACM0'
except:
    try:
        ser = serial.Serial(
            port='/dev/ttyACM1',
            baudrate = 115200,
            timeout=1
        )
        print 'ttyACM1'
    except:
        try:
            ser = serial.Serial(
                baudrate = 115200,
                port='/dev/ttyACM2',
                timeout=1
            )
            print 'ttyACM2'
        except:
            try:
                ser = serial.Serial(
                    baudrate = 115200,
                    port='/dev/ttyUSB0',
                    timeout=1
                )
                print 'ttyUSB0'
            except:
                pass

#if you only want to send data to arduino (i.e. a signal to move a servo)
def send( theinput ):
    ser.write( theinput )
    while True:
        try:
            time.sleep(0.01)
            break
        except:
            pass
    time.sleep(0.1)

#if you would like to tell the arduino that you would like to receive data from the arduino
def send_and_receive( theinput ):
    ser.write( theinput )
    while True:
        try:
            time.sleep(0.01)
            state = ser.readline()
            print state
            return state
        except:
            pass
    time.sleep(0.1)

def readlineCR(port):
    rv = ""
    while True:
        ch = port.read()
        if ch=='\r' or ch=='':
            return rv
        else:
            rv += ch
#if you would like to tell the arduino that you would like to receive data from the arduino
def receive(  ):
    while True:
        try:
            print "try to read..."
            time.sleep(0.01)
            state = readlineCR(ser)
            if len(state)>1:
                print "State: " + state
                if "playsound" in state:
                    os.system("clear > tty1")
                    plstr="cat t|omxplayer -o both --vol \"-200\" "
                    name=state.split(" ",1)[1]
                    name= "/home/pi/"+name
                    name=name.replace("\n", "")
                    name=name.replace("\r", "")
                    ender=" >> /dev/null &"
                    command= plstr 
                    command=command+ name 
                    command=command+ ender
                    print command
                    os.system(command)
                elif "pl1play" in state:
                    name=state.split(" ",1)[1]
                    name=name.replace("\n", "")
                    name=name.replace("\r", "")
                    name= "/home/pi/"+name
                    global player1
                    player1= OMXPlayer(name)
                    player1.play()
                    print command
                elif "pl2play" in state:
                    name=state.split(" ",1)[1]
                    name=name.replace("\n", "")
                    name=name.replace("\r", "")
                    name= "/home/pi/"+name
                    global player2
                    player2 = OMXPlayer(name)
                    player2.play()
                    print command
                elif "pl3play" in state:
                    name=state.split(" ",1)[1]
                    name=name.replace("\n", "")
                    name=name.replace("\r", "")
                    name= "/home/pi/"+name
                    global player3
                    player3 = OMXPlayer(name)
                    player3.play()
                    print command
                elif "stoppl1" in state:
                    vol =0
                    while(vol<6000):
                        vol=vol+150
                        player1.set_volume(0,-vol)
                        time.sleep(0.1)
                    player1.pause()
                    player1.quit()
                    print command
                elif "stoppl2" in state:
                    vol =0
                    while(vol<6000):
                        vol=vol+150
                        player2.set_volume(0,-vol)
                        time.sleep(0.1)
                    player2.pause()
                    player2.quit()
                    print command
                elif "stoppl3" in state:
                    vol =0
                    while(vol<6000):
                        vol=vol+150
                        player3.set_volume(0,-vol)
                        time.sleep(0.1)
                    player3.pause()
                    player3.quit()
                    print command
                elif "stopsound" in state:
                    os.system("kill -9 `ps au | grep omxplayer | awk '{print $2}'`")
                    print command
                return state
            else:
                print "failed no data..."
                return "nodata"
        except Exception, e:
            time.sleep(0.1)  
            print ""
            print "Unexpected error:", str(e)
    
#f = open('dataFile.txt','a')
ser.flushInput()
while 1 :
    receive()

Answer 1

the whole script is spinning in while(true) of one def

That's where the problem is.