Python telling me thread assigned outside function isn't assigned-CodePudding

I made this program to have a timed input:

import time
from threading import Thread

def get_answer():
    answer = input ("ANSWER THE QUESTION!!!")

def runtime():
    time.sleep(1)
    timer = timer-1
    print (timer)
    if timer == 0:
        thread1.cancel()
        print ("hi")

timer = 5

# create two new threads
thread1 = Thread(target=get_answer)
thread2 = Thread(target=runtime)

# start the threads
thread1.start()
thread2.start()

# wait for the threads to complete
thread1.join()
thread2.join()

When I run it though, I get this error:

Exception in thread Thread-2 (runtime):
Traceback (most recent call last):
  File "C:\Users\user1\AppData\Local\Programs\Python\Python310\lib\threading.py", line 1009, in _bootstrap_inner
    self.run()
  File "C:\Users\user1\AppData\Local\Programs\Python\Python310\lib\threading.py", line 946, in run
    self._target(*self._args, **self._kwargs)
  File "c:\Users\user1\Desktop\import time.py", line 9, in runtime
    timer = timer-1
UnboundLocalError: local variable 'timer' referenced before assignment

How can I fix this? I set the variable timer before the thread runs, so why isn't it assigned already?

CodePudding user response：

I can not add a comment, I think you should use global var.

import time
from threading import Thread
global timer
timer = 5
# rest of your code 
def runtime():
    global timer
    time.sleep(1)
    timer = timer-1
    print (timer)
    if timer == 0:
        thread1.cancel()
        print ("hi")
#rest of your code

CodePudding user response：

Thanks @Marya

Made the variable global, and put the subtracting part in a while loop.

import time
from threading import Thread

global timer
timer = 5

def get_answer():
    answer = input ("ANSWER THE QUESTION!!!")

def runtime():
    global timer
    while True:
        time.sleep(1)
        timer = timer-1
        print (timer)
        if timer == 0:
            thread1.kill()
            thread1.join|()
            print ("hi")
            break

# create two new threads
thread1 = Thread(target=get_answer)
thread2 = Thread(target=runtime)

# start the threads
thread1.start()
thread2.start()

# wait for the threads to complete
thread1.join()
thread2.join()

CodePudding user response：

Here's how you can handle input with a timer:

import signal

TIMEOUT = 5

def get_answer(timeout):
    def handler(*args):
        raise Exception('Timeout')
    signal.signal(signal.SIGALRM, handler)
    signal.alarm(timeout)
    try:
        return input ("ANSWER THE QUESTION!!! ")
    except Exception:
        pass
    finally:
        signal.alarm(0)

print(get_answer(TIMEOUT))

So, no threads here. If no input within TIMEOUT seconds the get_answer() function will return None. Otherwise it will return the user input.