| Python 3.6.5 Documentation > "tempfile" — Generate temporary files and directories
"tempfile" — Generate temporary files and directories
*****************************************************
**Source code:** Lib/tempfile.py
======================================================================
This module creates temporary files and directories. It works on all
supported platforms. "TemporaryFile", "NamedTemporaryFile",
"TemporaryDirectory", and "SpooledTemporaryFile" are high-level
interfaces which provide automatic cleanup and can be used as context
managers. "mkstemp()" and "mkdtemp()" are lower-level functions which
require manual cleanup.
All the user-callable functions and constructors take additional
arguments which allow direct control over the location and name of
temporary files and directories. Files names used by this module
include a string of random characters which allows those files to be
securely created in shared temporary directories. 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=None, prefix=None, dir=None)
Return a *file-like object* that can be used as a temporary storage
area. The file is created securely, using the same rules as
"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 either not created
at all or 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 resulting object can be used as a context manager (see
Examples). On completion of the context or destruction of the file
object the temporary file will be removed from the filesystem.
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 have the same meaning
and defaults as with "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.
The "os.O_TMPFILE" flag is used if it is available and works
(Linux-specific, requires Linux kernel 3.11 or later).
Changed in version 3.5: The "os.O_TMPFILE" flag is now used if
available.
tempfile.NamedTemporaryFile(mode='w+b', buffering=None, encoding=None, newline=None, suffix=None, prefix=None, 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.
tempfile.SpooledTemporaryFile(max_size=0, mode='w+b', buffering=None, encoding=None, newline=None, suffix=None, prefix=None, 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()".
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 an "io.BytesIO" or "io.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.
Changed in version 3.3: the truncate method now accepts a "size"
argument.
tempfile.TemporaryDirectory(suffix=None, prefix=None, dir=None)
This function securely creates a temporary directory using the same
rules as "mkdtemp()". The resulting object can be used as a context
manager (see Examples). 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. When the returned object is used as a context
manager, the "name" will be assigned to the target of the "as"
clause in the "with" statement, if there is one.
The directory can be explicitly cleaned up by calling the
"cleanup()" method.
New in version 3.2.
tempfile.mkstemp(suffix=None, prefix=None, 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 not "None", 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 not "None", the file name will begin with that
prefix; otherwise, a default prefix is used. The default is the
return value of "gettempprefix()" or "gettempprefixb()", as
appropriate.
If *dir* is not "None", 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 any of *suffix*, *prefix*, and *dir* are not "None", they must
be the same type. If they are bytes, the returned name will be
bytes instead of str. If you want to force a bytes return value
with otherwise default behavior, pass "suffix=b''".
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.
Changed in version 3.5: *suffix*, *prefix*, and *dir* may now be
supplied in bytes in order to obtain a bytes return value. Prior
to this, only str was allowed. *suffix* and *prefix* now accept and
default to "None" to cause an appropriate default value to be used.
tempfile.mkdtemp(suffix=None, prefix=None, 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.
Changed in version 3.5: *suffix*, *prefix*, and *dir* may now be
supplied in bytes in order to obtain a bytes return value. Prior
to this, only str was allowed. *suffix* and *prefix* now accept and
default to "None" to cause an appropriate default value to be used.
tempfile.gettempdir()
Return the name of the directory used for temporary files. This
defines the default value for the *dir* argument to all functions
in this module.
Python searches a standard list of directories to find 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.
The result of this search is cached, see the description of
"tempdir" below.
tempfile.gettempdirb()
Same as "gettempdir()" but the return value is in bytes.
New in version 3.5.
tempfile.gettempprefix()
Return the filename prefix used to create temporary files. This
does not contain the directory component.
tempfile.gettempprefixb()
Same as "gettempprefix()" but the return value is in bytes.
New in version 3.5.
The module uses a global variable to store the name of the directory
used for temporary files returned by "gettempdir()". It can be set
directly to override the selection process, but this is discouraged.
All functions in this module take a *dir* argument which can be used
to specify the directory and this is the recommended approach.
tempfile.tempdir
When set to a value other than "None", this variable defines the
default value for the *dir* argument to the functions defined in
this module.
If "tempdir" is unset or "None" at any call to any of the above
functions except "gettempprefix()" it is initialized following the
algorithm described in "gettempdir()".
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
Deprecated functions and variables
==================================
A historical way to create temporary files was to first generate a
file name with the "mktemp()" function and then create a file using
this name. Unfortunately this is not secure, because a different
process may create a file with this name in the time between the call
to "mktemp()" and the subsequent attempt to create the file by the
first process. The solution is to combine the two steps and create the
file immediately. This approach is used by "mkstemp()" and the other
functions described above.
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 similar to those of "mkstemp()", except that bytes file names,
"suffix=None" and "prefix=None" are not supported.
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
| 
