multithreading - Python Threading task handling -

i have created 3 threads in python run infinitely. how can check of 3 threads finished processing current task?

def 1thread():     global list     while true:        if len(list) != 0:           list.pop()           # takes long        else:           pass 

on above code, example, want check if 1thread() "doing takes long" or wainting "list" have elements. thinking of method 1thread().busy

any ideas? script background processing allows more tasks que.