Python多处理输出
[英]Python multiprocessing output
问题描述
I have a progress bar function. 
我有进度条功能。 I would like to run this progress bar while the other function is doing processing. 我想在其他功能正在处理时运行此进度栏。 I have written a simple test code using multiprocessing module and it was not working well. 我已经使用多处理模块编写了一个简单的测试代码，但效果不佳。 My code: 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()
I was hoping that foo will print the current time first. 我希望foo首先打印当前时间。 Then progress_bar comes in to countdown for 10 seconds. 然后progress_bar进入倒数10秒钟。 Finally foo will output another time at the end. 最终foo将在末尾输出另一个时间。
Tue Apr 5 11:49:47 2016
100% =================================================>|
Tue Apr 5 11:49:57 2016
However what I got from the output is something like this: 但是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% =================================================>|
Is there a way to fix this in Python? 有没有办法在Python中解决此问题？ Thank you very much! 非常感谢你！
2 个解决方案
解决方案1
1 2016-04-05 19:10:22
This is happening because the function parameters are evaluated first, and when defining your p1 and p2 you're actually calling foo1('this') which executes the function at the definition of p1 , and progress_bar() at the instantiation of p2 . 之所以发生这种情况，是因为首先评估了函数参数，并且在定义p1和p2 ，实际上是在调用foo1('this') ，它在p1的定义处执行函数，并在p2的实例化处执行progress_bar() 。
For a simple example that demonstrates this, see below: 有关演示此内容的简单示例，请参见下文：
def fn():
print 'called'
return 1
target1 = fn()
target = fn
print target1
print target
This prints: 打印：
>>> 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
I got your example working with Thread s below ( Edit : After looking into some Process examples , it seems that they should work with the same syntax as the below code (just change the import and use Process instead of Thread ), but for some reason I just can't get the Process approach to print, even after copying the example. Might be due to my custom python setup, but not entirely sure.): 我在下面得到了使用Thread的示例（ 编辑 ：在研究了一些Process 示例之后 ，似乎它们应使用与以下代码相同的语法（只需更改导入并使用Process而不是Thread ），但是由于某些原因即使复制示例后，我也无法打印出Process方法。这可能是由于我自定义的python设置，但不是完全确定。）：
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()
This prints 此打印
Tue Apr 05 15:09:34 2016
('1% | |',)
('2% |> |',)
('3% |> |',)
('4% |=> |',)
('5% |=> |',)
('6% |==> |',)
('7% |==> |',)
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('10% |====> |',)
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Tue Apr 05 15:09:44 2016
('99% |================================================> |',)
('100%|=================================================>|',)
解决方案2
1 已采纳 2016-04-05 19:13:18
Try this: 尝试这个：
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()
Notice the different p1 Process. 注意不同的p1进程。
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