Threads in python?

Question

Python

Two threads are accessing the same list. One sees it empty, and the other shows that there is data in it. Why is this happening and how to deal with it.
this is not the whole code, but I’ll try to explain, execute adds a function to the list, and run (runs in a separate thread) executes and writes the answer to the dictionary, the problem is that the execute function adds to the list, but from the thread where run the list remains empty. I will say in advance with Queue a similar situation

tail = []
response = {}



def run():
    print(123)
    while True:
        try:
            if len(tail) > 0:
                for i in range(95):
                    func = tail.pop()
                    response.update({id(func) : func()})
                    time.sleep(1)
        except IndexError:
            pass
        except Exception as e:
            print(e)

def execute(self , func):
    global tail #что с global что без , тоже самое
    tail.append(func)
    while True:
        if response.get(id(func)) != None:
            return response.get(id(func))