arduino delay using python

#python code:
import serial  #pyserial
from tkinter import *
import datetime

win = Tk()
win.geometry("400x400+1200+300")
bg_color ="gray"
frame = Frame(win,width=400,height=400,bg=bg_color)
frame.place(x=0,y=0)
ser = serial.Serial('COM3', '9600')
SHOW_DATE = Label(frame,font=('Arial',15,'bold'),bg=bg_color,fg="white")
SHOW_DATE.place(x=100,y=10)
def run():
    now = datetime.datetime.now()
    Date_now = now.strftime("%Y-%m-%d")
    Time_now = now.strftime("%H :%M :%S")
    SHOW_DATE['text']="date : "+Date_now + "\n"+"time : " + Time_now
    m = now.strftime("%M")
    if m == "08":
        frame['bg']="red"
        ser.write('f'.encode('utf-8'))
    if m == "09":
        frame['bg'] = bg_color
        ser.write('x'.encode('utf-8'))
    SHOW_DATE.after(10, run)

run()
win.mainloop()

####################
#arduino code:
int leds[4]={11,10,9,3};
void setup() {
for (int i= 0 ;i<=5;i++){
  pinMode(leds[i],OUTPUT);

  Serial.begin(9600);
}
}

void loop() {
if (Serial.available()>0){
  char ch = Serial.read();
  if(ch =='f'){

    digitalWrite(leds[0],HIGH);
    
  }
  
  else{
    for(int i=0;i<=5;i++){
      digitalWrite(leds[i],LOW);
    }
  }
}
}