10.6. "tempfile" — Generate temporary files and directories
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**Source code:** Lib/tempfile.py

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

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,
"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 functions:

tempfile.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 "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
   "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'[, bufsize=-1[, 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 returned file-
   like 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.

   New in version 2.3.

   New in version 2.6: The *delete* parameter.

tempfile.SpooledTemporaryFile([max_size=0[, mode='w+b'[, bufsize=-1[, 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 "StringIO" object 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.

   New in version 2.6.

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.

   New in version 2.3.

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.

   New in version 2.3.

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
        <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 a global variable 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 RiscOS, the directory named by the "Wimp$ScrapDir"
        environment variable.

      * 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.

   New in version 2.3.

tempfile.template

   Deprecated since version 2.0: Use "gettempprefix()" instead.

   When set to a value other than "None", this variable defines the
   prefix of the final component of the filenames returned by
   "mktemp()".  A string of six random letters and digits is appended
   to the prefix to make the filename unique. The default prefix is
   "tmp".

   Older versions of this module used to require that "template" be
   set to "None" after a call to "os.fork()"; this has not been
   necessary since version 1.5.2.

tempfile.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.

   New in version 1.5.2.
