Problem in sending and receiving commands from PC to Arduino via usb serial

Question

I am trying to send commands and receive data from Arduino beta Metro M4 express (programmed using circuitpython) via USB. The version of circuitpython is 4.0.1 and Python version is 3.7.3. I could able to send the data via usb but having problems while receiving the data. The command 'supervisor.runtime.serial_bytes_available' reads the command sent from PC via usb but I am receiving the data printed using 'print' statement in the python shell. Also, I cannot able to get and print the command using in 'data = sys.stdin.read(4)' command. Any help is much appreciated.

My python code is as follows:

import serial
import time
while(1):
    ser = serial.Serial(port='COM9', baudrate=115200, timeout=0.01)

    cmd = b'what'
    print('cmd=', cmd)    
    ser.write(cmd)
    ser.flushInput()   
    time.sleep(1)

    x = ser.readline()
    print("received1: ",x.decode("utf-8"))
    y = ser.readline()
    print("received2: ",y.decode("utf-8"))   
    ser.close()

Circuitpython code is as follows:

import supervisor
while(x):
    if supervisor.runtime.serial_bytes_available:

        print("True")
        data = sys.stdin.read(4)
        print("in code.py",data)

The expected and results received in the python shell are as follows: Expected result is: received1: True, received2: what Received results: cmd= b'what' received1: hat received2:
cmd= b'what' received1: hat received2:
cmd= b'what' received1: hat received2:
cmd= b'what' received1: hat received2:
cmd= b'what' received1: hat received2:
cmd= b'what'