option to leave tempfile.NamedTemporaryFile around on close

[djmdjm]

BPO	1537850
Nosy	@brettcannon, @birkenfeld
Files	tempfile.diff: Add optional 'delete' argument to NamedTemporaryFile constructor python-tempfile.diff: Diff with regress test

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2007-03-13.18:32:06.000>
created_at = <Date 2006-08-10.06:57:31.000>
labels = ['library']
title = 'option to leave tempfile.NamedTemporaryFile around on close'
updated_at = <Date 2007-03-13.18:32:06.000>
user = 'https://bugs.python.org/djmdjm'

bugs.python.org fields:

activity = <Date 2007-03-13.18:32:06.000>
actor = 'georg.brandl'
assignee = 'none'
closed = True
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2006-08-10.06:57:31.000>
creator = 'djmdjm'
dependencies = []
files = ['7456', '7457']
hgrepos = []
issue_num = 1537850
keywords = ['patch']
message_count = 8.0
messages = ['50852', '50853', '50854', '50855', '50856', '50857', '50858', '50859']
nosy_count = 3.0
nosy_names = ['brett.cannon', 'georg.brandl', 'djmdjm']
pr_nums = []
priority = 'normal'
resolution = 'accepted'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue1537850'
versions = ['Python 2.5']

[djmdjm]

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)

[djmdjm]

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

[brettcannon]

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

[djmdjm]

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

[djmdjm]

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Here is an diff that includes a regress test

[brettcannon]

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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.

[djmdjm]

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Well, that would a) not be an atomic replacement and b) you
miss (or would have to reimplement) the mkstemp() like
behaviour.

[birkenfeld]

Thanks for the patch, committed with doc changes as rev. 54344.