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:mod:`tempfile` --- Generate temporary files and directories
============================================================
.. sectionauthor:: Zack Weinberg <zack@codesourcery.com>
.. module:: tempfile
:synopsis: Generate temporary files and directories.
.. index::
pair: temporary; file name
pair: temporary; file
This module generates temporary files and directories. It works on all
supported platforms. It provides three new functions,
:func:`NamedTemporaryFile`, :func:`mkstemp`, and :func:`mkdtemp`, which should
eliminate all remaining need to use the insecure :func:`mktemp` function.
Temporary file names created by this module no longer contain the process ID;
instead a string of six random characters is used.
Also, all the user-callable functions now take additional arguments which
allow direct control over the location and name of temporary files. It is
no longer necessary to use the global *tempdir* and *template* variables.
To maintain backward compatibility, the argument order is somewhat odd; it
is recommended to use keyword arguments for clarity.
The module defines the following user-callable functions:
.. function:: TemporaryFile(mode='w+b', buffering=None, encoding=None, newline=None, suffix='', prefix='tmp', dir=None)
Return a :term:`file-like object` that can be used as a temporary storage area.
The file is created using :func:`mkstemp`. It will be destroyed as soon
as it is closed (including an implicit close when the object is garbage
collected). Under Unix, the directory entry for the file is removed
immediately after the file is created. Other platforms do not support
this; your code should not rely on a temporary file created using this
function having or not having a visible name in the file system.
The *mode* parameter defaults to ``'w+b'`` so that the file created can
be read and written without being closed. Binary mode is used so that it
behaves consistently on all platforms without regard for the data that is
stored. *buffering*, *encoding* and *newline* are interpreted as for
:func:`open`.
The *dir*, *prefix* and *suffix* parameters are passed to :func:`mkstemp`.
The returned object is a true file object on POSIX platforms. On other
platforms, it is a file-like object whose :attr:`!file` attribute is the
underlying true file object. This file-like object can be used in a
:keyword:`with` statement, just like a normal file.
.. function:: NamedTemporaryFile(mode='w+b', buffering=None, encoding=None, newline=None, suffix='', prefix='tmp', dir=None, delete=True)
This function operates exactly as :func:`TemporaryFile` does, except that
the file is guaranteed to have a visible name in the file system (on
Unix, the directory entry is not unlinked). That name can be retrieved
from the :attr:`name` member of the file object. Whether the name can be
used to open the file a second time, while the named temporary file is
still open, varies across platforms (it can be so used on Unix; it cannot
on Windows NT or later). If *delete* is true (the default), the file is
deleted as soon as it is closed.
The returned object is always a file-like object whose :attr:`!file`
attribute is the underlying true file object. This file-like object can
be used in a :keyword:`with` statement, just like a normal file.
.. function:: SpooledTemporaryFile(max_size=0, mode='w+b', buffering=None, encoding=None, newline=None, suffix='', prefix='tmp', dir=None)
This function operates exactly as :func:`TemporaryFile` does, except that
data is spooled in memory until the file size exceeds *max_size*, or
until the file's :func:`fileno` method is called, at which point the
contents are written to disk and operation proceeds as with
:func:`TemporaryFile`.
The resulting file has one additional method, :func:`rollover`, which
causes the file to roll over to an on-disk file regardless of its size.
The returned object is a file-like object whose :attr:`_file` attribute
is either a :class:`StringIO` object or a true file object, depending on
whether :func:`rollover` has been called. This file-like object can be
used in a :keyword:`with` statement, just like a normal file.
.. function:: mkstemp(suffix='', prefix='tmp', dir=None, text=False)
Creates a temporary file in the most secure manner possible. There are
no race conditions in the file's creation, assuming that the platform
properly implements the :const:`os.O_EXCL` flag for :func:`os.open`. The
file is readable and writable only by the creating user ID. If the
platform uses permission bits to indicate whether a file is executable,
the file is executable by no one. The file descriptor is not inherited
by child processes.
Unlike :func:`TemporaryFile`, the user of :func:`mkstemp` is responsible
for deleting the temporary file when done with it.
If *suffix* is specified, the file name will end with that suffix,
otherwise there will be no suffix. :func:`mkstemp` does not put a dot
between the file name and the suffix; if you need one, put it at the
beginning of *suffix*.
If *prefix* is specified, the file name will begin with that prefix;
otherwise, a default prefix is used.
If *dir* is specified, the file will be created in that directory;
otherwise, a default directory is used. The default directory is chosen
from a platform-dependent list, but the user of the application can
control the directory location by setting the *TMPDIR*, *TEMP* or *TMP*
environment variables. There is thus no guarantee that the generated
filename will have any nice properties, such as not requiring quoting
when passed to external commands via ``os.popen()``.
If *text* is specified, it indicates whether to open the file in binary
mode (the default) or text mode. On some platforms, this makes no
difference.
:func:`mkstemp` returns a tuple containing an OS-level handle to an open
file (as would be returned by :func:`os.open`) and the absolute pathname
of that file, in that order.
.. function:: mkdtemp(suffix='', prefix='tmp', dir=None)
Creates a temporary directory in the most secure manner possible. There
are no race conditions in the directory's creation. The directory is
readable, writable, and searchable only by the creating user ID.
The user of :func:`mkdtemp` is responsible for deleting the temporary
directory and its contents when done with it.
The *prefix*, *suffix*, and *dir* arguments are the same as for
:func:`mkstemp`.
:func:`mkdtemp` returns the absolute pathname of the new directory.
.. function:: mktemp(suffix='', prefix='tmp', dir=None)
.. deprecated:: 2.3
Use :func:`mkstemp` instead.
Return an absolute pathname of a file that did not exist at the time the
call is made. The *prefix*, *suffix*, and *dir* arguments are the same
as for :func:`mkstemp`.
.. warning::
Use of this function may introduce a security hole in your program. By
the time you get around to doing anything with the file name it returns,
someone else may have beaten you to the punch. :func:`mktemp` usage can
be replaced easily with :func:`NamedTemporaryFile`, passing it the
``delete=False`` parameter::
>>> f = NamedTemporaryFile(delete=False)
>>> f
<open file '<fdopen>', mode 'w+b' at 0x384698>
>>> f.name
'/var/folders/5q/5qTPn6xq2RaWqk+1Ytw3-U+++TI/-Tmp-/tmpG7V1Y0'
>>> f.write("Hello World!\n")
>>> f.close()
>>> os.unlink(f.name)
>>> os.path.exists(f.name)
False
The module uses two global variables that tell it how to construct a
temporary name. They are initialized at the first call to any of the
functions above. The caller may change them, but this is discouraged; use
the appropriate function arguments, instead.
.. data:: tempdir
When set to a value other than ``None``, this variable defines the
default value for the *dir* argument to all the functions defined in this
module.
If ``tempdir`` is unset or ``None`` at any call to any of the above
functions, Python searches a standard list of directories and sets
*tempdir* to the first one which the calling user can create files in.
The list is:
#. The directory named by the :envvar:`TMPDIR` environment variable.
#. The directory named by the :envvar:`TEMP` environment variable.
#. The directory named by the :envvar:`TMP` environment variable.
#. A platform-specific location:
* On Windows, the directories :file:`C:\\TEMP`, :file:`C:\\TMP`,
:file:`\\TEMP`, and :file:`\\TMP`, in that order.
* On all other platforms, the directories :file:`/tmp`, :file:`/var/tmp`, and
:file:`/usr/tmp`, in that order.
#. As a last resort, the current working directory.
.. function:: gettempdir()
Return the directory currently selected to create temporary files in. If
:data:`tempdir` is not ``None``, this simply returns its contents; otherwise,
the search described above is performed, and the result returned.
.. function:: gettempprefix()
Return the filename prefix used to create temporary files. This does not
contain the directory component.
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