线程在 Python 3.6 中没有输出

Question

Here's my code:

import _thread
import time
def print_time(name, delay):
    count=1
    while count<=5:
        time.delay(delay)
        print ("Thread %s Time is %s"%(count, time.ctime(time.time())))
        count = count+1

_thread.start_new_thread(print_time,("T-1",2))
_thread.start_new_thread(print_time,("T-2",4))

The output should be various lines telling the current time. But after running the program I got no output and no error. Why is this happening? I use Python 3.6.

Answer 1

Probably the first question is why you're using _thread . I am guessing your issue is that your main thread finishes before print_time manages to produce any output, and on this particular system, that exits the whole program.

From the section Caveats in the _thread documentation :

When the main thread exits, it is system defined whether the other threads survive. On most systems, they are killed without executing try … finally clauses or executing object destructors.

When using threading instead, you get to choose whether to await threads with the daemon argument.

Answer 2

上面的答案总是更好的选择，但如果你仍然坚持使用_thread模块，只需在代码末尾添加time.sleep(1)延迟主线程

Answer 3

Use threading :

import threading
import time

def print_time(name, delay):
    count=1
    while count<=5:
        time.sleep(delay)
        print ("Thread %s Time is %s"%(count, time.ctime(time.time())))
        count = count+1

t1 = threading.Thread(target=print_time, args=("T-1",2))
t2 = threading.Thread(target=print_time, args=("T-2",4))

t1.start()
t2.start()

The threading module provides an easier to use and higher-level threading API built on top of this [ _thread ] module.