tempfile — Generate temporary files and directories (original) (raw)

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 ascontext managers. mkstemp() andmkdtemp() 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=-1, encoding=None, newline=None, suffix=None, prefix=None, dir=None, *, errors=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 (seeExamples). 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, errors and newline are interpreted as foropen().

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).

On platforms that are neither Posix nor Cygwin, TemporaryFile is an alias for NamedTemporaryFile.

Raises an auditing event tempfile.mkstemp with argument fullpath.

Changed in version 3.5: The os.O_TMPFILE flag is now used if available.

Changed in version 3.8: Added errors parameter.

tempfile.NamedTemporaryFile(mode='w+b', buffering=-1, encoding=None, newline=None, suffix=None, prefix=None, dir=None, delete=True, *, errors=None, delete_on_close=True)

This function operates exactly as TemporaryFile() does, except the following differences:

The returned object is always a file-like object whose fileattribute is the underlying true file object. This file-like object can be used in a with statement, just like a normal file. The name of the temporary file can be retrieved from the name attribute of the returned file-like object. On Unix, unlike with theTemporaryFile(), the directory entry does not get unlinked immediately after the file creation.

If delete is true (the default) and delete_on_close is true (the default), the file is deleted as soon as it is closed. If delete is true and delete_on_close is false, the file is deleted on context manager exit only, or else when the file-like object is finalized. Deletion is not always guaranteed in this case (see object.__del__()). If delete is false, the value of delete_on_close is ignored.

Therefore to use the name of the temporary file to reopen the file after closing it, either make sure not to delete the file upon closure (set the_delete_ parameter to be false) or, in case the temporary file is created in a with statement, set the delete_on_close parameter to be false. The latter approach is recommended as it provides assistance in automatic cleaning of the temporary file upon the context manager exit.

Opening the temporary file again by its name while it is still open works as follows:

On Windows, if delete_on_close is false, and the file is created in a directory for which the user lacks delete access, then the os.unlink()call on exit of the context manager will fail with a PermissionError. This cannot happen when delete_on_close is true because delete access is requested by the open, which fails immediately if the requested access is not granted.

On POSIX (only), a process that is terminated abruptly with SIGKILL cannot automatically delete any NamedTemporaryFiles it created.

Raises an auditing event tempfile.mkstemp with argument fullpath.

Changed in version 3.8: Added errors parameter.

Changed in version 3.12: Added delete_on_close parameter.

class tempfile.SpooledTemporaryFile(max_size=0, mode='w+b', buffering=-1, encoding=None, newline=None, suffix=None, prefix=None, dir=None, *, errors=None)

This class 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 withTemporaryFile().

rollover()

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.TextIOWrapper 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.

Changed in version 3.8: Added errors parameter.

Changed in version 3.11: Fully implements the io.BufferedIOBase andio.TextIOBase abstract base classes (depending on whether binary or text mode was specified).

class tempfile.TemporaryDirectory(suffix=None, prefix=None, dir=None, ignore_cleanup_errors=False, *, delete=True)

This class securely creates a temporary directory using the same rules as mkdtemp(). The resulting object can be used as a context manager (seeExamples). 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.

name

The directory name can be retrieved from the name attribute of the returned object. When the returned object is used as a context manager, thename will be assigned to the target of the as clause in the with statement, if there is one.

cleanup()

The directory can be explicitly cleaned up by calling thecleanup() method. If ignore_cleanup_errors is true, any unhandled exceptions during explicit or implicit cleanup (such as aPermissionError removing open files on Windows) will be ignored, and the remaining removable items deleted on a “best-effort” basis. Otherwise, errors will be raised in whatever context cleanup occurs (the cleanup() call, exiting the context manager, when the object is garbage-collected or during interpreter shutdown).

The delete parameter can be used to disable cleanup of the directory tree upon exiting the context. While it may seem unusual for a context manager to disable the action taken when exiting the context, it can be useful during debugging or when you need your cleanup behavior to be conditional based on other logic.

Raises an auditing event tempfile.mkdtemp with argument fullpath.

Added in version 3.2.

Changed in version 3.10: Added ignore_cleanup_errors parameter.

Changed in version 3.12: Added the delete parameter.

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 ofgettempprefix() 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 notNone, 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 and true, the file is opened in text mode. Otherwise, (the default) the file is opened in binary mode.

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.

Raises an auditing event tempfile.mkstemp with argument fullpath.

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.

Changed in version 3.6: The dir parameter now accepts a path-like object.

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 formkstemp().

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

Raises an auditing event tempfile.mkdtemp with argument fullpath.

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.

Changed in version 3.6: The dir parameter now accepts a path-like object.

Changed in version 3.12: mkdtemp() now always returns an absolute path, even if dir is relative.

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 oftempdir below.

Changed in version 3.10: Always returns a str. Previously it would return any tempdirvalue regardless of type so long as it was not None.

tempfile.gettempdirb()

Same as gettempdir() but the return value is in bytes.

Added 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.

Added 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. This is the recommended approach that does not surprise other unsuspecting code by changing global API behavior.

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, including its type, bytes or str. It cannot be apath-like object.

If tempdir is None (the default) at any call to any of the above functions except gettempprefix() it is initialized following the algorithm described in gettempdir().

Note

Beware that if you set tempdir to a bytes value, there is a nasty side effect: The global default return type ofmkstemp() and mkdtemp() changes to bytes when no explicit prefix, suffix, or dir arguments of type str are supplied. Please do not write code expecting or depending on this. This awkward behavior is maintained for compatibility with the historical implementation.

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 file using a context manager

close the file, use the name to open the file again

with tempfile.NamedTemporaryFile(delete_on_close=False) as fp: ... fp.write(b'Hello world!') ... fp.close() ... # the file is closed, but not removed ... # open the file again by using its name ... with open(fp.name, mode='rb') as f: ... f.read() b'Hello world!'

file is now 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=Noneand 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 thedelete=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