How can I delay execution until after os.system finishes?

Question

I am using os.system to copy a file from a system to another. The logic of a very simple program is to execute another set of commands after this file gets copied.

The problem is that os.system does not actually wait for the file to be copied, and gets to executing the next line. This causes issues to the system. I could actually give some wait functions, through time.sleep(), but we have to copy files with sizes ranging from 500 MB to sometimes 20 GB, and the times taken are very different.

What's the solution? I need to somehow tell my program that the files are copied, and then to execute the next line.

os.system does wait for the command to complete. What command are you using for the copy? — payne, Jan 29 '11 at 13:39
Does "from a system to another" mean via the network? What protocol? Or is it from on file system to another? — Sven Marnach, Jan 29 '11 at 13:45

score 6 · Answer 1 · answered Jan 29 '11 at 13:38

The first thing I'd try is to use shutil.copyfile() instead of an external program to copy the file. If you have to use an external program, you should call it via subprocess.Popen(), not via os.system(). You can use the Popen.wait() to wait for the subprocess to finish.

score 1 · Answer 2 · answered Jan 29 '11 at 13:37

1

I think you should rather use shutil.copyfile than os.system to copy a file.

(Edit: woops, copy, not move)

answered Jan 29 '11 at 13:37

Matti Virkkunen

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-1 He said "from a system to another". shutil only works on the same system. – payne Jan 29 '11 at 13:39
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@payne: Depends. You can move items from one system to another using NFS or SSHFS mounts, for instance. OP didn't provide much details. – Matti Virkkunen Jan 29 '11 at 13:40
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Technically true. But at this stage, we're both guessing what's in the OP's head. :-) – payne Jan 29 '11 at 13:41

score 1 · Answer 3 · answered Jan 29 '11 at 16:58

use the shutil module for copying files.

The shutil module offers a number of high-level operations on files and collections of files. In particular, functions are provided which support file copying and removal.

also, use the subprocess module instead of os.system()

The subprocess module allows you to spawn new processes, connect to their input/output/error pipes, and obtain their return codes. This module intends to replace several other, older modules and functions, such as:

os.system

for a better answer, you need to provide more detail about what exactly you are trying to do and how (programmatically) you are stuck.

How can I delay execution until after os.system finishes?

3 Answers3

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