
``tempfile`` --- Generate temporary files and directories
*********************************************************

**Source code:** Lib/tempfile.py

======================================================================

This module generates temporary files and directories.  It works on
all supported platforms.  It provides three new functions,
``NamedTemporaryFile()``, ``mkstemp()``, and ``mkdtemp()``, which
should eliminate all remaining need to use the insecure ``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 items:

tempfile.TemporaryFile(mode='w+b', buffering=None, encoding=None, newline=None, suffix='', prefix='tmp', dir=None)

   Return a *file-like object* that can be used as a temporary storage
   area. The file is created using ``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 ``open()``.

   The *dir*, *prefix* and *suffix* parameters are passed to
   ``mkstemp()``.

   The returned object is a true file object on POSIX platforms.  On
   other platforms, it is a file-like object whose ``file`` attribute
   is the underlying true file object. This file-like object can be
   used in a ``with`` statement, just like a normal file.

tempfile.NamedTemporaryFile(mode='w+b', buffering=None, encoding=None, newline=None, suffix='', prefix='tmp', dir=None, delete=True)

   This function operates exactly as ``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 ``name`` attribute 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
   ``file`` attribute is the underlying true file object. This file-
   like object can be used in a ``with`` statement, just like a normal
   file.

tempfile.SpooledTemporaryFile(max_size=0, mode='w+b', buffering=None, encoding=None, newline=None, suffix='', prefix='tmp', dir=None)

   This function operates exactly as ``TemporaryFile()`` does, except
   that data is spooled in memory until the file size exceeds
   *max_size*, or until the file's ``fileno()`` method is called, at
   which point the contents are written to disk and operation proceeds
   as with ``TemporaryFile()``.  Also, it's ``truncate`` method does
   not accept a ``size`` argument.

   The resulting file has one additional method, ``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 ``_file`` attribute
   is either a ``BytesIO`` or ``StringIO`` object (depending on
   whether binary or text *mode* was specified) or a true file object,
   depending on whether ``rollover()`` has been called.  This file-
   like object can be used in a ``with`` statement, just like a normal
   file.

tempfile.TemporaryDirectory(suffix='', prefix='tmp', dir=None)

   This function creates a temporary directory using ``mkdtemp()``
   (the supplied arguments are passed directly to the underlying
   function). The resulting object can be used as a context manager
   (see *With Statement Context Managers*).  On completion of the
   context (or destruction of the temporary directory object), the
   newly created temporary directory and all its contents are removed
   from the filesystem.

   The directory name can be retrieved from the ``name`` attribute of
   the returned object.

   The directory can be explicitly cleaned up by calling the
   ``cleanup()`` method.

   New in version 3.2.

tempfile.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 ``os.O_EXCL`` flag for
   ``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 ``TemporaryFile()``, the user of ``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.  ``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.

   ``mkstemp()`` returns a tuple containing an OS-level handle to an
   open file (as would be returned by ``os.open()``) and the absolute
   pathname of that file, in that order.

tempfile.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 ``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
   ``mkstemp()``.

   ``mkdtemp()`` returns the absolute pathname of the new directory.

tempfile.mktemp(suffix='', prefix='tmp', dir=None)

   Deprecated since version 2.3: Use ``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 ``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.  ``mktemp()`` usage can be replaced easily with
     ``NamedTemporaryFile()``, passing it the ``delete=False``
     parameter:

        >>> f = NamedTemporaryFile(delete=False)
        >>> f.name
        '/tmp/tmptjujjt'
        >>> f.write(b"Hello World!\n")
        13
        >>> 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.

tempfile.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:

   1. The directory named by the ``TMPDIR`` environment variable.

   2. The directory named by the ``TEMP`` environment variable.

   3. The directory named by the ``TMP`` environment variable.

   4. A platform-specific location:

      * On Windows, the directories ``C:\TEMP``, ``C:\TMP``,
        ``\TEMP``, and ``\TMP``, in that order.

      * On all other platforms, the directories ``/tmp``,
        ``/var/tmp``, and ``/usr/tmp``, in that order.

   5. As a last resort, the current working directory.

tempfile.gettempdir()

   Return the directory currently selected to create temporary files
   in. If ``tempdir`` is not ``None``, this simply returns its
   contents; otherwise, the search described above is performed, and
   the result returned.

tempfile.gettempprefix()

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


Examples
========

Here are some examples of typical usage of the ``tempfile`` module:

   >>> import tempfile

   # create a temporary file and write some data to it
   >>> fp = tempfile.TemporaryFile()
   >>> fp.write(b'Hello world!')
   # read data from file
   >>> fp.seek(0)
   >>> fp.read()
   b'Hello world!'
   # close the file, it will be removed
   >>> fp.close()

   # create a temporary file using a context manager
   >>> with tempfile.TemporaryFile() as fp:
   ...     fp.write(b'Hello world!')
   ...     fp.seek(0)
   ...     fp.read()
   b'Hello world!'
   >>>
   # file is now closed and removed

   # create a temporary directory using the context manager
   >>> with tempfile.TemporaryDirectory() as tmpdirname:
   ...     print('created temporary directory', tmpdirname)
   >>>
   # directory and contents have been removed
