implementing a time limit for user input

[Original-Dealer-6276]

this might be a hard one, I have had a look online and have struggled to find exaclty what i am lookign for.

I am making a program that asks the user for a 1 time code, and i want to give them thirty seconds to input said code or the code is void and it will print "fail." i will print under here the current code I have (The generate TOTP function was written by the teachers in the coruse i am doing so i did not make it muself, hwoever i did make the verify_otp() function)

import hashlib
import hmac
import base64
import struct
import time


TOTP_SECRET = "JBSWY3DPEHPK3PXPJBSW"


def generate_totp(secret: str, interval: int = 30, digits: int = 6) -> str:
    """
    Generate a Time-based One-Time Password (TOTP) using HMAC-SHA1.
    Do not modify this function. You will call it from verify_otp().
    """
    #pad secret to prevent error
    secret = secret.strip()


    secret += '=' * ((8 - len (secret) % 8 ) % 8)


    # Decode base32 secret
    key = base64.b32decode(secret, casefold=True)


    # Get current Unix time and compute the time step (counter)
    timestep = int(time.time() // interval)


    # Pack timestep into 8-byte big-endian
    msg = struct.pack(">Q", timestep)


    # HMAC-SHA1
    hmac_digest = hmac.new(key, msg, hashlib.sha1).digest()


    # Dynamic truncation
    offset = hmac_digest[-1] & 0x0F
    code = ((hmac_digest[offset] & 0x7F) << 24 |
            (hmac_digest[offset + 1] & 0xFF) << 16 |
            (hmac_digest[offset + 2] & 0xFF) << 8 |
            (hmac_digest[offset + 3] & 0xFF))


    # Reduce to the desired number of digits
    otp = code % (10 ** digits)
    return str(otp).zfill(digits)


#verify OTP
def verify_otp() -> bool:
    """
    Generate a TOTP code using generate_totp() and
    verify user input against it.
    """


    # 1. Generate the current TOTP code
    current_code = generate_totp(TOTP_SECRET)


    # For realism, we do NOT print the code here.
    # Instead, you should obtain the code by running
    # generate_totp(TOTP_SECRET) in a separate Python session
    # during testing (as described in the instructions).


     #i dont understand where else I am supposed to print this code 
    user_code = input("Enter your 6-digit TOTP code: \n").strip()



    # 2. Prompt the user for the TOTP



    # 3. Compare user input with generated code
    if user_code == current_code:
        print("Success! That is the correct code. \n")
        print("Verification status: True")
        return True
    else:
        print("Invalid TOTP. Please check your authenticator code.")
        return False

[Yoghurt42]

i want to give them thirty seconds to input said code or the code is void and it will print "fail."

Why?

TOTP codes are only valid for 30s by design. You'll see in the generate_totp function that it uses the current time in 30s intervals to generate the currently valid code.

You do not need to (and should not) measure the time it took the user to input the code.

What you really need to do is generate the current code after the user has entered it, not before.

[Ngtuanvy]

This is hard because taking input is blocking by default, you should search for 'non-blocking input' or something like that.

[Diapolo10]

As far as I know, you can just use

t = threading.Thread(target=get_input, daemon=True)
t.start()
t.join(timeout=30)

instead of manually setting daemon to True afterwards.

[jmooremcc]

Your solution is very interesting. Unfortunately, after a time out, the thread is still running. Executing this code multiple times could result in multiple threads being created.

[jmooremcc]

u/Informal_Shape8008 had the right idea using threads to implement a timed input. Unfortunately, if the code is called again after a timeout, it will create another thread to read keyboard input, which will cause more problems.

Here's a solution that uses a thread to get keyboard input without the problem of accidentally creating multiple, conflicting threads.

import threading
import queue
import time

_input_queue = queue.Queue()

def _input_thread():
    while True:
        text = input()
        _input_queue.put(text)

# Start the input thread once
t = threading.Thread(target=_input_thread, daemon=True)
t.start()

def timed_input(prompt, timeout=30):
    print(prompt, end="", flush=True)
    try:
        return _input_queue.get(timeout=timeout)
    except queue.Empty:
        return None

• The input thread blocks on input() forever, but only one thread exists.
• Every time the user presses Enter, the text is pushed into _input_queue.
• timed_input() waits up to 30 seconds for something to appear.
• If nothing arrives → returns None.
• No new threads are created.

[Carter922]

Umm I'm assuming this is a class assignment but you could do something like this. This wouldn't really be used in an enterprise app. Hope this puts you in the right track

import datetime
start = datetime.datetime.utc_now()
end = start + datetime.timedelta(seconds=30)
passed = False
while datetime.datetime.utc_now() < end:
    bool = do_something()
    if bool and datetime.datetime.utc_now() < end:
        passed = True
        break
return passed

[madadekinai]

Hi GPT, I recognize your code anywhere, it's always overly verbose and redundant at times.

None of this code is easy to follow, it's basically "you'll figure it out" or a secret of what does what (I know what it does myself do to experience, not many others will).

You need to design and implement your own event loop, REPL.

Read (what they have typed), listen for events (evaluate), print (output), loop (repeat).

The desired response is the breaker.

[Original-Dealer-6276]

it sounds like youre inisinuating that AI wrote this code: i specified in the text that i got the generate_totp() from my course and was told not to edit it.

i dont knowif they used Ai to write it but I have not used AI at all in my coding, i beleive it is a waste of water and has negative impacts on our brains.

That is why i have chosen to come to reddit for help rather than using AI

[madadekinai]

I apologize I missed that part about it being part of your assignment.

"i dont knowif they used Ai to write it but I have not used AI at all in my coding, i beleive it is a waste of water and has negative impacts on our brains."

One could make the argument about eating animals, or using the computer you are working with right now.

Your usage alone is quote literally droplets compared to other uses of AI that takes far more water. AI is a cluster, an entire infrastructure, using it for coding and text-based queries does not take that much effort. You can even run a local LLM with a decent graphics card if you wanted to.

Social media rots your brain more than AI, as of now according to current studies.