Python子进程:如何三次使用管道? [英] Python subprocess: how to use pipes thrice?

问题描述

我想在以下行上使用子进程:

I'd like to use subprocess on the following line:

convert ../loxie-orig.png bmp:- | mkbitmap -f 2 -s 2 -t 0.48 | potrace -t 5 --progress -s -o ../DSC00232.svg

我发现感谢其他帖子子流程文档，但是在该示例中，我们仅使用了两次管道.

I found thank to other posts the subprocess documentation but in the example we use only twice pipe.

所以，我尝试使用三个命令中的两个，它可以工作

So, I try for two of the three commands and it works

p1 = subprocess.Popen(['convert', fileIn, 'bmp:-'], stdout=subprocess.PIPE)
# p2 = subprocess.Popen(['mkbitmap', '-f', '2', '-s', '2', '-t', '0.48'], stdout=subprocess.PIPE)
p3 = subprocess.Popen(['potrace', '-t' , '5', '-s' , '-o', fileOut], stdin=p1.stdout,stdout=subprocess.PIPE)
p1.stdout.close()  # Allow p1 to receive a SIGPIPE if p3 exits.
output = p3.communicate()[0]

您能帮我执行第三条命令吗?

Can you help me for the third command?

非常感谢您.

推荐答案

只需在同一示例之后添加第三条命令即可:

Just add a third command following the same example:

p1 = subprocess.Popen(['convert', fileIn, 'bmp:-'], stdout=subprocess.PIPE)
p2 = subprocess.Popen(['mkbitmap', '-f', '2', '-s', '2', '-t', '0.48'], 
     stdin=p1.stdout, stdout=subprocess.PIPE)
p1.stdout.close()
p3 = subprocess.Popen(['potrace', '-t' , '5', '-s' , '-o', fileOut],        
     stdin=p2.stdout,stdout=subprocess.PIPE)
p2.stdout.close()

output = p3.communicate()[0]

这篇关于Python子进程:如何三次使用管道?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！