answer = ""
while not(answer.startswith('Exe')): # maybe answer.startswith('Exe') or answer.startswith('Err') or 'something else'
   if answer.startswith('ussd') or answer.startswith('Ple'):
      continue
   answer+=sp.readline()

    def __init__(self,
                 port = None,           # number of device, numbering starts at
                                        # zero. if everything fails, the user
                                        # can specify a device string, note
                                        # that this isn't portable anymore
                                        # port will be opened if one is specified
                 baudrate=9600,         # baud rate
                 bytesize=EIGHTBITS,    # number of data bits
                 parity=PARITY_NONE,    # enable parity checking
                 stopbits=STOPBITS_ONE, # number of stop bits
                 timeout=None,          # set a timeout value, None to wait forever
                 xonxoff=0,             # enable software flow control
                 rtscts=0,              # enable RTS/CTS flow control
                 writeTimeout=None,     # set a timeout for writes
                 dsrdtr=None,           # None: use rtscts setting, dsrdtr override if true or false
                 interCharTimeout=None  # Inter-character timeout, None to disable
                 ):

    def readlines(self, sizehint=None, eol='\n'):
        """read a list of lines, until timeout
        sizehint is ignored"""
        if self.timeout is None:
            raise ValueError("Serial port MUST have enabled timeout for this function!")
        lines = []
        while 1:
            line = self.readline(eol=eol)
            if line:
                lines.append(line)
                if line[-1] != eol:    # was the line received with a timeout?
                    break
            else:
                break
        return lines

try:
    sp = serial.Serial(port="COM5",timeout=10)
except:
    print('Error: Device is busy')
    sys.exit()
if __name__ == '__main__':
    print('Please wait...')

    req = b'AT+CUSD=1,"*102#",15'
    sp.write(req+b"\r\n")
    res = b""
    ans = b""
    while 1:
        ans = sp.readline(eol=b"\n")
        if ans == b"" or ans == b"OK\r\n" or ans == b"ERROR\r\n":
            break
        if ans == b"\r\n" or ans == req + b"\r\r\n":
            continue
        res += ans

    print(res)
    sp.close()
    sys.exit()

answer = ""
result = ""
while not(answer.startswith('Exe')): # maybe answer.startswith('Exe') or answer.startswith('Err') or 'something else'
   answer = sp.readline()   
   if answer.startswith('ussd') or answer.startswith('Ple'):
      continue
   result += answer