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cpython/Lib/tempfile.py

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"""Temporary files.
This module provides generic, low- and high-level interfaces for
creating temporary files and directories. All of the interfaces
provided by this module can be used without fear of race conditions
except for 'mktemp'. 'mktemp' is subject to race conditions and
should not be used; it is provided for backward compatibility only.
The default path names are returned as str. If you supply bytes as
input, all return values will be in bytes. Ex:
>>> tempfile.mkstemp()
(4, '/tmp/tmptpu9nin8')
>>> tempfile.mkdtemp(suffix=b'')
b'/tmp/tmppbi8f0hy'
This module also provides some data items to the user:
TMP_MAX - maximum number of names that will be tried before
giving up.
tempdir - If this is set to a string before the first use of
any routine from this module, it will be considered as
another candidate location to store temporary files.
"""
__all__ = [
"NamedTemporaryFile", "TemporaryFile", # high level safe interfaces
"SpooledTemporaryFile", "TemporaryDirectory",
"mkstemp", "mkdtemp", # low level safe interfaces
"mktemp", # deprecated unsafe interface
"TMP_MAX", "gettempprefix", # constants
"tempdir", "gettempdir",
"gettempprefixb", "gettempdirb",
]
# Imports.
import functools as _functools
import warnings as _warnings
import io as _io
import os as _os
import shutil as _shutil
import errno as _errno
from random import Random as _Random
import weakref as _weakref
try:
import _thread
except ImportError:
import _dummy_thread as _thread
_allocate_lock = _thread.allocate_lock
_text_openflags = _os.O_RDWR | _os.O_CREAT | _os.O_EXCL
if hasattr(_os, 'O_NOFOLLOW'):
_text_openflags |= _os.O_NOFOLLOW
_bin_openflags = _text_openflags
if hasattr(_os, 'O_BINARY'):
_bin_openflags |= _os.O_BINARY
if hasattr(_os, 'TMP_MAX'):
TMP_MAX = _os.TMP_MAX
else:
TMP_MAX = 10000
# This variable _was_ unused for legacy reasons, see issue 10354.
# But as of 3.5 we actually use it at runtime so changing it would
# have a possibly desirable side effect... But we do not want to support
# that as an API. It is undocumented on purpose. Do not depend on this.
template = "tmp"
# Internal routines.
_once_lock = _allocate_lock()
if hasattr(_os, "lstat"):
_stat = _os.lstat
elif hasattr(_os, "stat"):
_stat = _os.stat
else:
# Fallback. All we need is something that raises OSError if the
# file doesn't exist.
def _stat(fn):
fd = _os.open(fn, _os.O_RDONLY)
_os.close(fd)
def _exists(fn):
try:
_stat(fn)
except OSError:
return False
else:
return True
def _infer_return_type(*args):
"""Look at the type of all args and divine their implied return type."""
return_type = None
for arg in args:
if arg is None:
continue
if isinstance(arg, bytes):
if return_type is str:
raise TypeError("Can't mix bytes and non-bytes in "
"path components.")
return_type = bytes
else:
if return_type is bytes:
raise TypeError("Can't mix bytes and non-bytes in "
"path components.")
return_type = str
if return_type is None:
return str # tempfile APIs return a str by default.
return return_type
def _sanitize_params(prefix, suffix, dir):
"""Common parameter processing for most APIs in this module."""
output_type = _infer_return_type(prefix, suffix, dir)
if suffix is None:
suffix = output_type()
if prefix is None:
if output_type is str:
prefix = template
else:
prefix = _os.fsencode(template)
if dir is None:
if output_type is str:
dir = gettempdir()
else:
dir = gettempdirb()
return prefix, suffix, dir, output_type
class _RandomNameSequence:
"""An instance of _RandomNameSequence generates an endless
sequence of unpredictable strings which can safely be incorporated
into file names. Each string is six characters long. Multiple
threads can safely use the same instance at the same time.
_RandomNameSequence is an iterator."""
characters = "abcdefghijklmnopqrstuvwxyz0123456789_"
@property
def rng(self):
cur_pid = _os.getpid()
if cur_pid != getattr(self, '_rng_pid', None):
self._rng = _Random()
self._rng_pid = cur_pid
return self._rng
def __iter__(self):
return self
def __next__(self):
c = self.characters
choose = self.rng.choice
letters = [choose(c) for dummy in range(8)]
return ''.join(letters)
def _candidate_tempdir_list():
"""Generate a list of candidate temporary directories which
_get_default_tempdir will try."""
dirlist = []
# First, try the environment.
for envname in 'TMPDIR', 'TEMP', 'TMP':
dirname = _os.getenv(envname)
if dirname: dirlist.append(dirname)
# Failing that, try OS-specific locations.
if _os.name == 'nt':
dirlist.extend([ r'c:\temp', r'c:\tmp', r'\temp', r'\tmp' ])
else:
dirlist.extend([ '/tmp', '/var/tmp', '/usr/tmp' ])
# As a last resort, the current directory.
try:
dirlist.append(_os.getcwd())
except (AttributeError, OSError):
dirlist.append(_os.curdir)
return dirlist
def _get_default_tempdir():
"""Calculate the default directory to use for temporary files.
This routine should be called exactly once.
We determine whether or not a candidate temp dir is usable by
trying to create and write to a file in that directory. If this
is successful, the test file is deleted. To prevent denial of
service, the name of the test file must be randomized."""
namer = _RandomNameSequence()
dirlist = _candidate_tempdir_list()
for dir in dirlist:
if dir != _os.curdir:
dir = _os.path.abspath(dir)
# Try only a few names per directory.
for seq in range(100):
name = next(namer)
filename = _os.path.join(dir, name)
try:
fd = _os.open(filename, _bin_openflags, 0o600)
try:
try:
with _io.open(fd, 'wb', closefd=False) as fp:
fp.write(b'blat')
finally:
_os.close(fd)
finally:
_os.unlink(filename)
return dir
except FileExistsError:
pass
except PermissionError:
# This exception is thrown when a directory with the chosen name
# already exists on windows.
if (_os.name == 'nt' and _os.path.isdir(dir) and
_os.access(dir, _os.W_OK)):
continue
break # no point trying more names in this directory
except OSError:
break # no point trying more names in this directory
raise FileNotFoundError(_errno.ENOENT,
"No usable temporary directory found in %s" %
dirlist)
_name_sequence = None
def _get_candidate_names():
"""Common setup sequence for all user-callable interfaces."""
global _name_sequence
if _name_sequence is None:
_once_lock.acquire()
try:
if _name_sequence is None:
_name_sequence = _RandomNameSequence()
finally:
_once_lock.release()
return _name_sequence
def _mkstemp_inner(dir, pre, suf, flags, output_type):
"""Code common to mkstemp, TemporaryFile, and NamedTemporaryFile."""
names = _get_candidate_names()
if output_type is bytes:
names = map(_os.fsencode, names)
for seq in range(TMP_MAX):
name = next(names)
file = _os.path.join(dir, pre + name + suf)
try:
fd = _os.open(file, flags, 0o600)
except FileExistsError:
continue # try again
except PermissionError:
# This exception is thrown when a directory with the chosen name
# already exists on windows.
if (_os.name == 'nt' and _os.path.isdir(dir) and
_os.access(dir, _os.W_OK)):
continue
else:
raise
return (fd, _os.path.abspath(file))
raise FileExistsError(_errno.EEXIST,
"No usable temporary file name found")
# User visible interfaces.
def gettempprefix():
"""The default prefix for temporary directories."""
return template
def gettempprefixb():
"""The default prefix for temporary directories as bytes."""
return _os.fsencode(gettempprefix())
tempdir = None
def gettempdir():
"""Accessor for tempfile.tempdir."""
global tempdir
if tempdir is None:
_once_lock.acquire()
try:
if tempdir is None:
tempdir = _get_default_tempdir()
finally:
_once_lock.release()
return tempdir
def gettempdirb():
"""A bytes version of tempfile.gettempdir()."""
return _os.fsencode(gettempdir())
def mkstemp(suffix=None, prefix=None, dir=None, text=False):
"""User-callable function to create and return a unique temporary
file. The return value is a pair (fd, name) where fd is the
file descriptor returned by os.open, and name is the filename.
If 'suffix' is specified, the file name will end with that suffix,
otherwise there will be no 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.
If 'text' is specified and true, the file is opened in text
mode. Else (the default) the file is opened in binary mode. On
some operating systems, this makes no difference.
suffix, prefix and dir must all contain the same type if specified.
If they are bytes, the returned name will be bytes; str otherwise.
A value of None will cause an appropriate default to be used.
The file is readable and writable only by the creating user ID.
If the operating system uses permission bits to indicate whether a
file is executable, the file is executable by no one. The file
descriptor is not inherited by children of this process.
Caller is responsible for deleting the file when done with it.
"""
prefix, suffix, dir, output_type = _sanitize_params(prefix, suffix, dir)
if text:
flags = _text_openflags
else:
flags = _bin_openflags
return _mkstemp_inner(dir, prefix, suffix, flags, output_type)
def mkdtemp(suffix=None, prefix=None, dir=None):
"""User-callable function to create and return a unique temporary
directory. The return value is the pathname of the directory.
Arguments are as for mkstemp, except that the 'text' argument is
not accepted.
The directory is readable, writable, and searchable only by the
creating user.
Caller is responsible for deleting the directory when done with it.
"""
prefix, suffix, dir, output_type = _sanitize_params(prefix, suffix, dir)
names = _get_candidate_names()
if output_type is bytes:
names = map(_os.fsencode, names)
for seq in range(TMP_MAX):
name = next(names)
file = _os.path.join(dir, prefix + name + suffix)
try:
_os.mkdir(file, 0o700)
except FileExistsError:
continue # try again
except PermissionError:
# This exception is thrown when a directory with the chosen name
# already exists on windows.
if (_os.name == 'nt' and _os.path.isdir(dir) and
_os.access(dir, _os.W_OK)):
continue
else:
raise
return file
raise FileExistsError(_errno.EEXIST,
"No usable temporary directory name found")
def mktemp(suffix="", prefix=template, dir=None):
"""User-callable function to return a unique temporary file name. The
file is not created.
Arguments are as for mkstemp, except that the 'text' argument is
not accepted.
THIS FUNCTION IS UNSAFE AND SHOULD NOT BE USED. The file name may
refer to a file that did not exist at some point, but by the time
you get around to creating it, someone else may have beaten you to
the punch.
"""
## from warnings import warn as _warn
## _warn("mktemp is a potential security risk to your program",
## RuntimeWarning, stacklevel=2)
if dir is None:
dir = gettempdir()
names = _get_candidate_names()
for seq in range(TMP_MAX):
name = next(names)
file = _os.path.join(dir, prefix + name + suffix)
if not _exists(file):
return file
raise FileExistsError(_errno.EEXIST,
"No usable temporary filename found")
class _TemporaryFileCloser:
"""A separate object allowing proper closing of a temporary file's
underlying file object, without adding a __del__ method to the
temporary file."""
file = None # Set here since __del__ checks it
close_called = False
def __init__(self, file, name, delete=True):
self.file = file
self.name = name
self.delete = delete
# NT provides delete-on-close as a primitive, so we don't need
# the wrapper to do anything special. We still use it so that
# file.name is useful (i.e. not "(fdopen)") with NamedTemporaryFile.
if _os.name != 'nt':
# Cache the unlinker so we don't get spurious errors at
# shutdown when the module-level "os" is None'd out. Note
# that this must be referenced as self.unlink, because the
# name TemporaryFileWrapper may also get None'd out before
# __del__ is called.
def close(self, unlink=_os.unlink):
if not self.close_called and self.file is not None:
self.close_called = True
try:
self.file.close()
finally:
if self.delete:
unlink(self.name)
# Need to ensure the file is deleted on __del__
def __del__(self):
self.close()
else:
def close(self):
if not self.close_called:
self.close_called = True
self.file.close()
class _TemporaryFileWrapper:
"""Temporary file wrapper
This class provides a wrapper around files opened for
temporary use. In particular, it seeks to automatically
remove the file when it is no longer needed.
"""
def __init__(self, file, name, delete=True):
self.file = file
self.name = name
self.delete = delete
self._closer = _TemporaryFileCloser(file, name, delete)
def __getattr__(self, name):
# Attribute lookups are delegated to the underlying file
# and cached for non-numeric results
# (i.e. methods are cached, closed and friends are not)
file = self.__dict__['file']
a = getattr(file, name)
if hasattr(a, '__call__'):
func = a
@_functools.wraps(func)
def func_wrapper(*args, **kwargs):
return func(*args, **kwargs)
# Avoid closing the file as long as the wrapper is alive,
# see issue #18879.
func_wrapper._closer = self._closer
a = func_wrapper
if not isinstance(a, int):
setattr(self, name, a)
return a
# The underlying __enter__ method returns the wrong object
# (self.file) so override it to return the wrapper
def __enter__(self):
self.file.__enter__()
return self
# Need to trap __exit__ as well to ensure the file gets
# deleted when used in a with statement
def __exit__(self, exc, value, tb):
result = self.file.__exit__(exc, value, tb)
self.close()
return result
def close(self):
"""
Close the temporary file, possibly deleting it.
"""
self._closer.close()
# iter() doesn't use __getattr__ to find the __iter__ method
def __iter__(self):
# Don't return iter(self.file), but yield from it to avoid closing
# file as long as it's being used as iterator (see issue #23700). We
# can't use 'yield from' here because iter(file) returns the file
# object itself, which has a close method, and thus the file would get
# closed when the generator is finalized, due to PEP380 semantics.
for line in self.file:
yield line
def NamedTemporaryFile(mode='w+b', buffering=-1, encoding=None,
newline=None, suffix=None, prefix=None,
dir=None, delete=True):
"""Create and return a temporary file.
Arguments:
'prefix', 'suffix', 'dir' -- as for mkstemp.
'mode' -- the mode argument to io.open (default "w+b").
'buffering' -- the buffer size argument to io.open (default -1).
'encoding' -- the encoding argument to io.open (default None)
'newline' -- the newline argument to io.open (default None)
'delete' -- whether the file is deleted on close (default True).
The file is created as mkstemp() would do it.
Returns an object with a file-like interface; the name of the file
is accessible as file.name. The file will be automatically deleted
when it is closed unless the 'delete' argument is set to False.
"""
prefix, suffix, dir, output_type = _sanitize_params(prefix, suffix, dir)
flags = _bin_openflags
# Setting O_TEMPORARY in the flags causes the OS to delete
# the file when it is closed. This is only supported by Windows.
if _os.name == 'nt' and delete:
flags |= _os.O_TEMPORARY
(fd, name) = _mkstemp_inner(dir, prefix, suffix, flags, output_type)
try:
file = _io.open(fd, mode, buffering=buffering,
newline=newline, encoding=encoding)
return _TemporaryFileWrapper(file, name, delete)
except Exception:
_os.close(fd)
raise
if _os.name != 'posix' or _os.sys.platform == 'cygwin':
# On non-POSIX and Cygwin systems, assume that we cannot unlink a file
# while it is open.
TemporaryFile = NamedTemporaryFile
else:
# Is the O_TMPFILE flag available and does it work?
# The flag is set to False if os.open(dir, os.O_TMPFILE) raises an
# IsADirectoryError exception
_O_TMPFILE_WORKS = hasattr(_os, 'O_TMPFILE')
def TemporaryFile(mode='w+b', buffering=-1, encoding=None,
newline=None, suffix=None, prefix=None,
dir=None):
"""Create and return a temporary file.
Arguments:
'prefix', 'suffix', 'dir' -- as for mkstemp.
'mode' -- the mode argument to io.open (default "w+b").
'buffering' -- the buffer size argument to io.open (default -1).
'encoding' -- the encoding argument to io.open (default None)
'newline' -- the newline argument to io.open (default None)
The file is created as mkstemp() would do it.
Returns an object with a file-like interface. The file has no
name, and will cease to exist when it is closed.
"""
global _O_TMPFILE_WORKS
prefix, suffix, dir, output_type = _sanitize_params(prefix, suffix, dir)
flags = _bin_openflags
if _O_TMPFILE_WORKS:
try:
flags2 = (flags | _os.O_TMPFILE) & ~_os.O_CREAT
fd = _os.open(dir, flags2, 0o600)
except IsADirectoryError:
# Linux kernel older than 3.11 ignores the O_TMPFILE flag:
# O_TMPFILE is read as O_DIRECTORY. Trying to open a directory
# with O_RDWR|O_DIRECTORY fails with IsADirectoryError, a
# directory cannot be open to write. Set flag to False to not
# try again.
_O_TMPFILE_WORKS = False
except OSError:
# The filesystem of the directory does not support O_TMPFILE.
# For example, OSError(95, 'Operation not supported').
#
# On Linux kernel older than 3.11, trying to open a regular
# file (or a symbolic link to a regular file) with O_TMPFILE
# fails with NotADirectoryError, because O_TMPFILE is read as
# O_DIRECTORY.
pass
else:
try:
return _io.open(fd, mode, buffering=buffering,
newline=newline, encoding=encoding)
except:
_os.close(fd)
raise
# Fallback to _mkstemp_inner().
(fd, name) = _mkstemp_inner(dir, prefix, suffix, flags, output_type)
try:
_os.unlink(name)
return _io.open(fd, mode, buffering=buffering,
newline=newline, encoding=encoding)
except:
_os.close(fd)
raise
class SpooledTemporaryFile:
"""Temporary file wrapper, specialized to switch from BytesIO
or StringIO to a real file when it exceeds a certain size or
when a fileno is needed.
"""
_rolled = False
def __init__(self, max_size=0, mode='w+b', buffering=-1,
encoding=None, newline=None,
suffix=None, prefix=None, dir=None):
if 'b' in mode:
self._file = _io.BytesIO()
else:
# Setting newline="\n" avoids newline translation;
# this is important because otherwise on Windows we'd
# get double newline translation upon rollover().
self._file = _io.StringIO(newline="\n")
self._max_size = max_size
self._rolled = False
self._TemporaryFileArgs = {'mode': mode, 'buffering': buffering,
'suffix': suffix, 'prefix': prefix,
'encoding': encoding, 'newline': newline,
'dir': dir}
def _check(self, file):
if self._rolled: return
max_size = self._max_size
if max_size and file.tell() > max_size:
self.rollover()
def rollover(self):
if self._rolled: return
file = self._file
newfile = self._file = TemporaryFile(**self._TemporaryFileArgs)
del self._TemporaryFileArgs
newfile.write(file.getvalue())
newfile.seek(file.tell(), 0)
self._rolled = True
# The method caching trick from NamedTemporaryFile
# won't work here, because _file may change from a
# BytesIO/StringIO instance to a real file. So we list
# all the methods directly.
# Context management protocol
def __enter__(self):
if self._file.closed:
raise ValueError("Cannot enter context with closed file")
return self
def __exit__(self, exc, value, tb):
self._file.close()
# file protocol
def __iter__(self):
return self._file.__iter__()
def close(self):
self._file.close()
@property
def closed(self):
return self._file.closed
@property
def encoding(self):
try:
return self._file.encoding
except AttributeError:
if 'b' in self._TemporaryFileArgs['mode']:
raise
return self._TemporaryFileArgs['encoding']
def fileno(self):
self.rollover()
return self._file.fileno()
def flush(self):
self._file.flush()
def isatty(self):
return self._file.isatty()
@property
def mode(self):
try:
return self._file.mode
except AttributeError:
return self._TemporaryFileArgs['mode']
@property
def name(self):
try:
return self._file.name
except AttributeError:
return None
@property
def newlines(self):
try:
return self._file.newlines
except AttributeError:
if 'b' in self._TemporaryFileArgs['mode']:
raise
return self._TemporaryFileArgs['newline']
def read(self, *args):
return self._file.read(*args)
def readline(self, *args):
return self._file.readline(*args)
def readlines(self, *args):
return self._file.readlines(*args)
def seek(self, *args):
self._file.seek(*args)
@property
def softspace(self):
return self._file.softspace
def tell(self):
return self._file.tell()
def truncate(self, size=None):
if size is None:
self._file.truncate()
else:
if size > self._max_size:
self.rollover()
self._file.truncate(size)
def write(self, s):
file = self._file
rv = file.write(s)
self._check(file)
return rv
def writelines(self, iterable):
file = self._file
rv = file.writelines(iterable)
self._check(file)
return rv
class TemporaryDirectory(object):
"""Create and return a temporary directory. This has the same
behavior as mkdtemp but can be used as a context manager. For
example:
with TemporaryDirectory() as tmpdir:
...
Upon exiting the context, the directory and everything contained
in it are removed.
"""
def __init__(self, suffix=None, prefix=None, dir=None):
self.name = mkdtemp(suffix, prefix, dir)
self._finalizer = _weakref.finalize(
self, self._cleanup, self.name,
warn_message="Implicitly cleaning up {!r}".format(self))
@classmethod
def _cleanup(cls, name, warn_message):
_shutil.rmtree(name)
_warnings.warn(warn_message, ResourceWarning)
def __repr__(self):
return "<{} {!r}>".format(self.__class__.__name__, self.name)
def __enter__(self):
return self.name
def __exit__(self, exc, value, tb):
self.cleanup()
def cleanup(self):
if self._finalizer.detach():
_shutil.rmtree(self.name)
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