python3.x - python 代码运行顺序问题?
问题描述
有如下代码:
class Test:
def a(self):
time.sleep(random.uniform(1,3))
print('a done')
def b(self):
time.sleep(random.uniform(1,3))
print('b done')
def c(self):
time.sleep(random.uniform(1,3))
print('C done')
想以多线程的方式运行, 并计算运行时间:
def main():
task = Test()
task_list = [
task.a,
task.b,
task.c,
]
for i in task_list:
# i = run_time_log(i)
t = Thread(target=i)
t.start()
start = time.time()
main()
print(time.time() - start)
问题是,每次运行的时候都是先把最后的 print 弄出来,然后才会打印诸如 a done, b done 之类的信息
所以最终的问题是:如何可以正确的得到这段代码的运行时间,以及为什么会出现这种情况
Thread.join([timeout])
Wait until the thread terminates. This blocks the calling thread until the thread whose join() method is called terminates – either normally or through an unhandled exception – or until the optional timeout occurs.
When the timeout argument is present and not None, it should be a floating point number specifying a timeout for the operation in seconds (or fractions thereof). As join() always returns None, you must call isAlive() after join() to decide whether a timeout happened – if the thread is still alive, the join() call timed out.
When the timeout argument is not present or None, the operation will block until the thread terminates.
A thread can be join()ed many times.
join() raises a RuntimeError if an attempt is made to join the current thread as that would cause a deadlock. It is also an error to join() a thread before it has been started and attempts to do so raises the same exception.
代码只需要加一行,代码如下:
import time
from threading import Thread
import random
class Test:
def a(self):
time.sleep(random.uniform(1,3))
print('a done')
def b(self):
time.sleep(random.uniform(1,3))
print('b done')
def c(self):
time.sleep(random.uniform(1,3))
print('C done')
def main():
task = Test()
task_list = [
task.a,
task.b,
task.c,
]
for i in task_list:
t = Thread(target=i)
t.start()
t.join() # <-- 这里需要 join,主线程等待子线程执行完毕,没有就是你之前的情况
start = time.time()
main()
print(time.time() - start)
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