[Python-Dev] Destructors and Closing of File Objects (original) (raw)

Guido van Rossum guido at python.org
Sat Apr 27 05:20:04 CEST 2013

There are no guarantees in life. On the other hand: Don't worry, be happy.

On Fri, Apr 26, 2013 at 7:39 PM, Nikolaus Rath <Nikolaus at rath.org> wrote:

Guido van Rossum <guido at python.org> writes:

On Monday, April 15, 2013, Nikolaus Rath wrote:

Brian Curtin <brian at python.org javascript:;> writes: > On Fri, Apr 12, 2013 at 12:04 AM, Nikolaus Rath <Nikolaus at rath.orgjavascript:;> wrote: >> [ Note: I already asked this on_ _>> http://stackoverflow.com/questions/15917502 but didn't get any >> satisfactory answers] > > Sorry, but that's not a reason to repost your question to this list. > If you have to ask somewhere else, it would be python-list, aka, > comp.lang.python.

I figured it belonged here because the question is really about the internal implementation of file objects, which to me didn't seem like a question about using Python. But I'll give it a few days and send another mail there if still haven't found the answer by then. You got your answer 16 hours ago on S.O. I guess you are referring to http://stackoverflow.com/a/15968516/293003 from Armin Ringo? ,---- | On Windows, NamedTemporaryFile uses a Windows-specific extension | (os.OTEMPORARY) to ensure that the file is deleted when it is closed. | This probably also works if the process is killed in any way. However | there is no obvious equivalent on POSIX, most likely because on POSIX | you can simply delete files that are still in use; it only deletes the | name, and the file's content is only removed after it is closed (in any | way). But indeed assuming that we want the file name to persist until | the file is closed, like with NamedTemporaryFile, then we need "magic". | | We cannot use the same magic as for flushing buffered files. What occurs | there is that the C library handles it (in Python 2): the files are FILE | objects in C, and the C guarantees that they are flushed on normal | program exit (but not if the process is killed). In the case of Python | 3, there is custom C code to achieve the same effect. But it's specific | to this use case, not anything directly reusable. [...] `---- It's indeed very informative, but it doesn't fully address the question because of the pyio module which certainly can't use any custom C code. Does that mean that when I'm using x = pyio.BufferedWriter(), I could loose data in the write buffer when the interpreter exits without me calling x.close(), but when using x = io.BufferedWriter(), the buffer is guaranteed to get flushed? (Note: this isn't a complaint, just curiosity about the Python internals). Best, -Nikolaus -- »Time flies like an arrow, fruit flies like a Banana.« PGP fingerprint: 5B93 61F8 4EA2 E279 ABF6 02CF A9AD B7F8 AE4E 425C

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