Python Serial.write 在 function 中不起作用

Question

I am trying to write to the serial port in the Start function to be received by some Arduino code. The problem occurs when the Calculate function also contains the serial.write command. The function is doing what it is supposed to otherwise but doesn't actually write to the serial port. (I pretty new at coding for reference)

Here is my python code:

import tkinter as tk
import serial
import time

serialPortController = serial.Serial('COM7',38400)
time.sleep(3)

controllerStatus = 0
netTankFlow = 0
currentTankHeight = 50.0

#Calculation Function__________________________________________________________________________________
def Calculate():
    global currentTankHeight
    
    if currentTankHeight == 0.0:
        serialPortController.write(b'10')
    elif currentTankHeight <= 20:
        serialPortController.write(b'11')
    elif currentTankHeight <= 40:
        serialPortController.write(b'12')
    elif currentTankHeight <= 60:
        serialPortController.write(b'13')
    elif currentTankHeight <= 80:
        serialPortController.write(b'14')
    else:
        serialPortController.write(b'15')
        
    tankControllerWindow.update() 
    tankControllerWindow.after(500, Calculate)

#Start & Quit Functions________________________________________________________________________________
def Start():
    global controllerStatus
    startButton.place_forget()
    controllerStatusLabel["text"] = "Controller Status: Active"
    controllerStatusLabel["bg"] = 'lawngreen'
    controllerStatusLabel["fg"] = 'black'
    controllerStatus = 1
    Calculate()
    serialPortController.write(b'41')
            
def Exit():
    quit()

#GUI Window Parameters & Variables_____________________________________________________________________
tankControllerWindow = tk.Tk()
windowWidth = 405
windowHeight = 255
tankControllerWindow.title('Tank Control Interface')
tankControllerWindow.minsize(windowWidth,windowHeight)
tankControllerWindow.configure(bg='whitesmoke')

guiXposition1 = 15
guiXposition4 = guiXposition1 + 300
guiYposition1 = 15


#Start and Exit Buttons________________________________________________________________________________
startButton = tk.Button(text="Start",command=Start)
startButton.place(x=guiXposition1,y=guiYposition1)

controllerStatusLabel = tk.Label(text="Controller Status: Inactive",
                                 bg='darkred',fg='white',width=20,justify='left')
controllerStatusLabel.place(x=guiXposition1+40,y=guiYposition1+2)

exitButton = tk.Button(text="Exit",command=Exit)
exitButton.place(x=guiXposition4+5,y=guiYposition1)

tankControllerWindow.mainloop()

And the Arduino Code for testing it

byte input;

void setup() {
  
  Serial.begin(38400);
  
  pinMode(led, OUTPUT);
  digitalWrite(led, HIGH);
}


void loop() {
  
  if (Serial.available() > 0) {
    input = Serial.parseInt();
  }

  if (input == 41) {
    Command();
  } 

}

void Command(){
  digitalWrite(led, LOW);
}

Answer 1

Changing .write(b'41') to .write(b'\n41') resolved the problem. Credit to jasonharper. Thanks!