Using Python and Arduino to change delay of light bulb via Serial - python-3.x

Question

I am using an Arduino Mega and python 3.7 on Windows 10 64-bit. I am trying to make a light bulb blink using python and pyserial. I want the light bulb to stay on for a x amount of time and turn off for an y amount of time. I enter the values in a python Tkinter program: https://pastebin.com/zkRmcP60 full code. after I've entered the values I send into the Arduino via this code:
import msgpack
import serial
arduionoData = serial.Serial('com3', 9600, timeout=1)
def sendlower(*args):
try:
global arduionoData
arduionoData.write(b"1")
while arduionoData.readline().decode() != "Send Next":
pass
first = int(firstdelay.get())
arduionoData.write(msgpack.packb(first, use_bin_type=True))
except ValueError:
print("Only Positive Integers")
def senduppper(*args):
try:
global arduionoData
arduionoData.write(b"2")
while arduionoData.readline().decode() != "Send Next":
pass
second = int(seconddelay.get())
arduionoData.write(msgpack.packb(second, use_bin_type=True))
except ValueError:
print("Only Positive Integers")
The Tkinter program executes the functions above visit Pastebin for entire code.
First I specify the mode or whether or not it's going to be the on delay or the off delay changing.
With this code (Setup and other code omitted please look in the paste bin for it.)
void readdelay(){
mode = Serial.parseInt();
if (mode == 1){
delay(200);
Serial.write("Send Next");
delay1 = Serial.parseInt();
}else if (mode == 2){
delay(200);
Serial.write("Send Next");
delay2 = Serial.parseInt();
}
}
void loop() {
if (Serial.available() > 0){
readdelay();
}
}
Right now if I send in any positive number into the program it either turns off(when i send in a number for the on delay) the light completely or turns it on(when I send in a number for the off delay). My guess is that whenever the Serial.parseInt(); the function gets the wrong type of input it interprets it as a zero.

Answer 1

The documentation says:
If no valid digits were read when the time-out (see Serial.setTimeout()) > occurs, 0 is returned;
It seems the parseInt fails, therefor the delay is set to 0, which is why the light goes completely on or off.
Another possibility it that the arduino only recieves the first character, which means the light switches so fast you cant see it. (Issue described here)
Try printing out what value is received by the arduino. It should tell you what is happening and what direction to go to solve it.