python - Python：运行进度条并同时工作？

Question

我想知道如何同时运行进度条和其他一些工作，然后当工作完成后，在 Python (2.7.x) 中停止进度条

import sys, time
def progress_bar():
 while True:
  for c in ['-','\\','|','/']:
   sys.stdout.write('\r' + "Working " + c)
   sys.stdout.flush()
   time.sleep(0.2)

def work():
 *doing hard work*

我怎么能做这样的事情：

progress_bar() #run in background?
work()
*stop progress bar*
print "\nThe work is done!"

Answer 1

您可以使用threading模块在后台运行线程。例如：

def run_progress_bar(finished_event):
    chars = itertools.cycle(r'-\|/')
    while not finished_event.is_set():
        sys.stdout.write('\rWorking ' + next(chars))
        sys.stdout.flush()
        finished_event.wait(0.2)


# somewhere else...
finished_event = threading.Event()
progress_bar_thread = threading.Thread(target=run_progress_bar, args=(finished_event,))
progress_bar_thread.start()
# do stuff
finished_event.set()
progress_bar_thread.join()

Answer 2

您可以创建一个单独的线程来显示进度条。这可以如@icktoofay 的回答中所示完成，但是我更喜欢下面的实现，它为任务派生一个新的线程子类。这种方法的一个优点是所有内容都包含在新类的每个实例中，因此您不需要全局变量来进行它们与主线程之间的通信。

import sys
import threading
import time

class ProgressBarThread(threading.Thread):
    def __init__(self, label='Working', delay=0.2):
        super(ProgressBarThread, self).__init__()
        self.label = label
        self.delay = delay  # interval between updates
        self.running = False
    def start(self):
        self.running = True
        super(ProgressBarThread, self).start()
    def run(self):
        label = '\r' + self.label + ' '
        while self.running:
            for c in ('-', '\\', '|', '/'):
                sys.stdout.write(label + c)
                sys.stdout.flush()
                time.sleep(self.delay)
    def stop(self):
        self.running = False
        self.join()  # wait for run() method to terminate
        sys.stdout.write('\r' + len(self.label)*' ' + '\r')  # clean-up
        sys.stdout.flush()

def work():
    time.sleep(5)  # *doing hard work*

pb_thread = ProgressBarThread('Computing')
pb_thread.start()
work()
pb_thread.stop()
print("The work is done!")