Question

我有一个进度条功能。我想在另一个函数正在处理时运行此进度条。我使用多处理模块编写了一个简单的测试代码，但效果不佳。我的代码：

from multiprocessing import Process
import time

def foo(thread):
    print time.ctime()
    time.sleep(10)
    print time.ctime()

def progress_bar(timer = 10):
    digits = 4
    delete = '\b' * 6
    time_slot = float(timer) / 100
    for i in range(1, 101):
        delete_bar = '\b' * 52
        if i == 1:
            bar = '|' + ' ' * 50 + '|'
        else:
            bar = '|' + '=' * (i / 2 - 1) + '>' + ' ' * (50 - i / 2) + '|'
        print "{0}{1:{2}}{3}{4}".format(delete, str(i) + '%', digits, bar, delete_bar),
        time.sleep(time_slot)
    print ''

def main():
    p1 = Process(target = foo1('this'))
    p1.start()
    p2 = Process(target = progress_bar())
    p2.start()
    p1.join()
    p2.join()

if __name__ == "__main__":
    main()

我希望foo会先打印当前时间。然后progress_bar进入倒计时10秒钟。最后，foo将在最后输出另一个时间。

Tue Apr  5 11:49:47 2016
100% =================================================>|
Tue Apr  5 11:49:57 2016

然而，我从输出中得到的是这样的：

Tue Apr  5 11:49:47 2016
Tue Apr  5 11:49:57 2016
100% =================================================>|

有没有办法在Python中解决这个问题？非常感谢你！

Answer 1

这种情况正在发生，因为首先评估函数参数，并在定义p1和p2时实际调用foo1('this')，它在{{1}的定义下执行函数在p1的实例化中{}和progress_bar()。

有关演示此内容的简单示例，请参阅以下内容：

p2

打印：

def fn():
    print 'called'
    return 1

target1 = fn()
target = fn

print target1
print target

我让您的示例使用下面的>>> called # Got called as soon as you called fn via fn() >>> 1 # Assigned the return value of fn to target1 >>> <function fn at 0x12DA77F0> # Didn't get called, assigned the fn definition to target（编辑：在查看了一些Thread examples后，似乎他们应该使用相同的语法如下面的代码（只需更改导入并使用Process而不是Process），但由于某种原因，即使在复制之后我也无法获得Thread方法进行打印例如。可能是由于我的自定义python设置，但不完全确定。）：

Process

打印

from threading import Thread
import time

def foo(thread):
    print(time.ctime())
    time.sleep(10)
    print(time.ctime())

def progress_bar(timer = 10):
    digits = 4
    delete = '\b' * 6
    time_slot = float(timer) / 100
    for i in range(1, 101):
        delete_bar = '\b' * 52
        if i == 1:
            bar = '|' + ' ' * 50 + '|'
        else:
            bar = '|' + '=' * (i / 2 - 1) + '>' + ' ' * (50 - i / 2) + '|'
        print("{0}{1:{2}}{3}{4}".format(delete, str(i) + '%', digits, bar, delete_bar),)
        time.sleep(time_slot)
    print('')

def main():
    t1 = Thread(target=foo, args=('this',)) # Notice, not foo('this') <- this executes foo('this') at definition
    t1.start()
    t2 = Thread(target=progress_bar) # Again, notice, no parens - target is just the function definition
    t2.start()
    t1.join()
    t2.join()

Answer 2

试试这个：

from multiprocessing import Process
import time

def foo1(thread):
    print time.ctime()
    time.sleep(10.5)
    print time.ctime()

def progress_bar(timer = 10):
    digits = 4
    delete = '\b' * 6
    time_slot = float(timer) / 100
    for i in range(1, 101):
        delete_bar = '\b' * 52
        if i == 1:
            bar = '|' + ' ' * 50 + '|'
        else:
            bar = '|' + '=' * (i / 2 - 1) + '>' + ' ' * (50 - i / 2) + '|'
        print "{0}{1:{2}}{3}{4}".format(delete, str(i) + '%', digits, bar, delete_bar),
        time.sleep(time_slot)
    print ''

def main():
    p1 = Process(target=foo1, args=('this',))
    # p1 = Process(target = foo1('this'))
    p1.start()
    time.sleep(0.1)
    p2 = Process(target=progress_bar)
    p2.start()
    p1.join()
    p2.join()

if __name__ == "__main__":
    main()

注意不同的p1过程。

Python多处理输出

2 个答案: