serial problem with python to arduino

Question

when i execute the python script, the arduino response but the code between the if(Serial.available()) not responding.

python script

 import  time, serial
 arduino = serial.Serial('COM7', 9600)
 time.sleep(2)
 while True:
    arduino.write(str(input("1")))                  # write position to serial port
    # and the pysthon script cant read the code below this line
    reachedPos = str(arduino.readline())            # read serial port for arduino echo
    data.append(reachedPos)
    arduino.close()

arduino script

 #include <Servo.h>
 Servo servo;
 int angle = 0;
 String in;
 int pos = 1;

void setup() {
 servo.attach(7);
 Serial.begin(9600);
 servo.write(0);

}


void loop() {

in = Serial.readStringUntil('\n');
Serial.print(in);
pos = in.toInt();

if(Serial.available())  // if data available in serial port
{
  if(pos == 1){
if(angle == 0){
  servo.write(180);               
  delay(10);
  angle = 180;
  delay(1000);
}

if(angle == 180){
  servo.write(0);
  delay(10);
  angle = 0;
  delay(1000);
}}
}
}

What is the problem? Te arduino code works fine