Reading serial data from Arduino by Python

Project Detail: I have a pushbutton and as I press it I am increasing a value and sending it over to python. However, no matter what I do, I can not get consistent data when it gets to Python.

Arduino Code:

void button(){
  int buttonState = digitalRead(buttonPin);
 

  if (buttonState == HIGH){
    
    index += 1;
    Serial.print("{" + String(index) + "}" + "\n");

    delay(1000);
    Serial.flush();
  }
}

Python Code:

def arduinoButton(newData):
    inProgress = False
    line = []

    while arduino.readline() != None and newData == False:
        rc = arduino.readline()
        print("rc", rc)

        for c in rc:
            print(c)
            if inProgress == True:
                if c != "}":
                    line.append(c)
                else:
                    inProgress = False
                    newData = True
                    print(line)
                    return line

            elif c == "{":
                inProgress = True

while True:
    newData = False
    num = arduinoButton(newData)

This is what is being received:
Screen Shot 2021-07-05 at 2.21.48 AM

However, what I am hoping for is getting {index} each time

Really appreciate any help!

This is what I have used to read a line of input from Arduino a line at a time.
Put a small delay in the Arduino sending code so only one line is sent at a time.
p.s. this is slightly edited from what I actually used

def haveLineOfData():
    # returns True if have received non-empty msg else False
    global receivedText, charsReceived, timeLastMsgRecived, clearToSendFlag
    
    receivedText = ""
    if serialPort.inWaiting() == 0:
        return False
    
    foundEOL = False
    while serialPort.inWaiting() > 0:  # have something to read
        x = serialPort.read().decode("utf-8") # decode needed for Python3
        if x == '\n':
            foundEOL = True
            break
        else:   
            charsReceived += x
            
    if foundEOL:
        #clear out any following data
        while serialPort.inWaiting() > 0:  # have something to read
            serialPort.read()
        
        if len(charsReceived) == 0:
            return False # empty msg returns False
        
        # else have non-empy msg and are connected
        receivedText = charsReceived
        charsReceived = ""
        return True

    # else still waiting for whole line
    return False

#==================

First step is to reduce the complexity of your "system" to the lowest possible level.
In this case this means instead of receiving the serial data in your python-script.

recieve the serial data in the serial monitor of the Arduino-IDE.
And look what data do you receive.

Next step is to use a minimalistic arduino-program that does send a fixed string to your python script testing if your python-script is able to receive this data.

Then adding a button to your Arduino-code sending a fixed text and again printing to the serial monitor of the Arduino-IDE. To test if your button is working as expected.

The more complexity to put together untested the more time you need to go through all the possabilities that might cause the problem. This time increases expontentially with the complexity.
So in the end you finish yor project faster by using really small tiny test-programs.

best regards Stefan