amt wrote:
I don't get it. If you don't close input and output it works exactly the same as if you would close them, so why do you have to do output.close() and input.close()?
(1) It is a matter of good programming practice. If you don't close them yourself, Python will eventually close them for you. In some versions of Python, that might be the instant they are no longer being used; in others, it might not happen for a long time. Under some circumstances, it might not happen at all.
(2) When writing to a file, the data may not be written to disk until the file is closed. When you say "output.write(...)", the data is often cached in memory and doesn't hit the hard drive until the file is closed[1]. The longer you keep the file open, the greater the chance that you will lose data.
(3) Since your operating system has strict limits on how many file handles can be kept open at any one instant, it is best to get into the habit of closing them when they aren't needed and not wait for "maid service" to clean up after you.
(4) Also, some operating systems (Windows, in particular) treat open files as locked and private. While you have a file open, no other program can also open it, even just to read the data. This spoils backup programs, anti-virus scanners, etc.
Also does it matter if you do: input.close() and then output.close()? Is there an order to follow?
It makes no real difference, but I prefer to close output files first, so they get written to disk a microsecond sooner than they otherwise would have.
[1] Annoyingly, modern hard drives often themselves have their own internal memory cache, so even when the operating system flushes data to the disk, there is no guarantee that the data will have actually been written to the disk platter. But there's nothing really you can do about that except hope that the power doesn't go out in the middle of writing to disk!
-- Steven _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
