using ffmpeg command line with python's subprocess module

[iMath]

在 2013年12月6日星期五UTC+8下午10时59分43秒，Chris Angelico写道：
> On Sat, Dec 7, 2013 at 1:54 AM, iMath <redstone-cold at 163.com> wrote:
> 
> >     fp=tempfile.NamedTemporaryFile(delete=False)
> 
> >     fp.write(("file '"+fileName1+"'\n").encode('utf-8'))
> 
> >     fp.write(("file '"+fileName2+"'\n").encode('utf-8'))
> 
> >
> 
> >
> 
> >     subprocess.call(['ffmpeg', '-f', 'concat','-i',fp.name, '-c',  'copy', fileName])
> 
> >     fp.close()
> 
> 
> 
> You need to close the file before getting the other process to use it.
> 
> Otherwise, it may not be able to open the file at all, and even if it
> 
> can, you might find that not all the data has been written.
> 
> 
> 
> But congrats! You have successfully found the points I was directing
> 
> you to. Yes, I was hinting that you need NamedTemporaryFile, the .name
> 
> attribute, and delete=False. Good job!
> 
> 
> 
> ChrisA

we don't have permission to use the temporary file while it has not been closed,but when the file is closed , it will be destroyed by default(delete=True),but once we set delete=False,then we couldn't depend on the convenience of letting the temporary file automatically delete itself after it has been used(then we have to delete it later by os.remove()) ,thus there is nearly no convenience in creating a temporary file or a persistent one when using NamedTemporaryFile.

I think this is a design flaw and should be improved like this :when delete=True,the file should be removed upon destruction of the object or on function return or on garbage collected,only when delete=False,the file can remain on the disk .