: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.

In version 2.3 of Python, this module was overhauled for enhanced security.  It

now 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'[, bufsize=-1[, suffix=''[, prefix='tmp'[, dir=None]]]]])

   Return a 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.  *bufsize* defaults to ``-1``, meaning that the operating system

   default is used.

   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'[, bufsize=-1[, 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.

   .. versionadded:: 2.3

   .. versionadded:: 2.6

      The *delete* parameter.

.. function:: SpooledTemporaryFile([max_size=0, [mode='w+b'[, bufsize=-1[, 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.

   .. versionadded:: 2.6

.. 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.

   .. versionadded:: 2.3

.. 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.

   .. versionadded:: 2.3

.. 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 RiscOS, the directory named by the :envvar:`Wimp$ScrapDir` environment

        variable.

      * 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.

   .. versionadded:: 2.3

.. data:: template

   .. deprecated:: 2.0

      Use :func:`gettempprefix` instead.

   When set to a value other than ``None``, this variable defines the prefix of the

   final component of the filenames returned by :func:`mktemp`.  A string of six

   random letters and digits is appended to the prefix to make the filename unique.

   The default prefix is :file:`tmp`.

   Older versions of this module used to require that ``template`` be set to

   ``None`` after a call to :func:`os.fork`; this has not been necessary since

   version 1.5.2.

.. function:: gettempprefix()

   Return the filename prefix used to create temporary files.  This does not

   contain the directory component.  Using this function is preferred over reading

   the *template* variable directly.

   .. versionadded:: 1.5.2