[Python] Communication between my arduino and my Python code doesn't seem to work

I need to use data collected from a sensor connected to an arduino Uno in a Python code. It's a basic question of getting the state of the digitalPin to my Python code. I first wanted to try my hand at just making a communication going both ways, from Python to Arduino, and after from Arduino to Python.

So I tried doing a ping-pong with Python sending a command, and Arduino sending back 0 if it didn't reach or 1 if it worked. The thing is: I can see the command test in Arduino, but the back data is not working.

Here's my Arduino code :

void setup() {
Serial.begin(9600);
delay(1000);
}

void loop() {

if (Serial.available() > 0) { // check if there's data from python
String command = Serial.readStringUntil('\n'); // read python command
Serial.println(command); // show command in Arduino monitor
Serial.write("command\n");
if (command == "test") { // if command is "test"
Serial.write(1);} // Envoie 1 en tant que byte
else {
Serial.write(0);} // Envoie 0 en tant que byte
Serial.flush();
}
}


And here's my Python code:

import serial
import time

capt = serial.Serial('COM5',9600,timeout=5)

def testcomm(test):
out = 0
com = (test + '\n').encode() # Send test command with end ligne indicator \n
print(f"Commande envoyée : {com}")
capt.write(com) # send command to Arduino
time.sleep(4)
# Check if there's data
if capt.in_waiting > 0 :
testout = capt.readline() # read
print(f'testout val (raw): {testout}') # show raw
if testout:
out = testout.strip() # clean answer
print(f'testout val (cleaned): {out}')
else:
print("Doesn't work")

return out

test1 = testcomm('test')
capt.close()


And here's the result in my Python console:

Commande envoyée : b'test\n'
Doesn't work


I checked whether the command line in itself worked inside the Arduino monitor, it does, and it sends back 1, but really, I can't read it in Python.

I also tried read(), readline() and readlines() just in case. I tried a lot of different things, but I didn't keep track, and I was also learning the pyserial library in parallel, so a lot of my tries were just weird. What can I try next?

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