Make a unique filesystem path, without creating the file

Thomas 'PointedEars' Lahn PointedEars at
Mon Feb 15 19:18:17 EST 2016

Gregory Ewing wrote:

> Ben Finney wrote:
>> One valid filesystem path each time it's accessed. That is, behaviour
>> equivalent to ‘tempfile.mktemp’.
>> My question is because the standard library clearly has this useful
>> functionality implemented, but simultaneously warns strongly against its
>> use.
> But it *doesn't*,

Yes, it does.

> if your requirement is truly to not touch the filesystem at all, because
> tempfile.mktemp() *reads* the file system to make sure the name it's
> returning isn't in use.

But there is a race condition occurring between the moment that the 
filesystem has been read and is being written to by another user.  Hence the 
deprecation in favor of tempfile.mkstemp() which also *creates* the file 
instead, and the warning about the security hole if tempfile.mktemp() is 
used anyway.

You can use tempfile.mktemp() only as long as it is irrelevant if a file 
with that name already exists, or exists later but was not created by you.


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