[Patches] [ python-Patches-1537850 ] option to leave tempfile.NamedTemporaryFile around on close

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Patches item #1537850, was opened at 2006-08-09 23:57
Message generated for change (Comment added) made by bcannon
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Category: Library (Lib)
Group: Python 2.5
Status: Open
Resolution: None
Priority: 5
Submitted By: Damien Miller (djmdjm)
Assigned to: Nobody/Anonymous (nobody)
Summary: option to leave tempfile.NamedTemporaryFile around on close

Initial Comment:
Hi,

tempfile.NamedTemporaryFile provides a good interface
to creating temporary files, but its insistence on
deleting the file upon close is limiting. The attached
patch adds an optional parameter to NamedTemporaryFile
that allows persistence of the temp file after it has
been closed.

One use-case that demonstrates where keeping the
temporary file around is handy would be when you need
to safely create and fill a temp file before it is
atomically moved into place with os.rename(). E.g.

def update_conf(conf_path):
    old = open(conf_path)
    tmp = tempfile.NamedTemporaryFile(prefix =
os.basename(conf_path), \
        dir = os.dirname(conf_path), delete = False)
    for l in old:
        tmp.write(l.replace('war', 'peace'))
    close(old)
    close(tmp)
    os.link(conf_path, conf_path + ".old")
    os.rename(tmp.name, conf_path)


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>Comment By: Brett Cannon (bcannon)
Date: 2006-08-25 23:40

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Right, it doesn't create a filesystem file.  But that is the
point.  You work in memory and then write to your final
destination as needed.  Your code you have pasted in the
description does nothing special that requires the use of a
temporary file.  You can just write into a StringIO object,
skip the os.link call, and then just write out to the final
file location.

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Comment By: Damien Miller (djmdjm)
Date: 2006-08-24 21:27

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Here is an diff that includes a regress test

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Comment By: Damien Miller (djmdjm)
Date: 2006-08-24 17:22

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As far as I can tell, StringIO doesn't actually create a
filesystem object that can be manipulated.

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Comment By: Brett Cannon (bcannon)
Date: 2006-08-24 16:52

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Why can't you store into an instance of StringIO instead of
a temp file?

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Comment By: Damien Miller (djmdjm)
Date: 2006-08-09 23:58

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oops, wrong Category: this should be Lib and not Modules

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