Python uses _wfopen()
(Python 2 open()
function) or _wopen()
(Python 3 and io.open()
) internally when opening files, neither of which allow for specifying any sharing flags. Sharing is thus set to a default, and what that default is does not appear to be documented.
If you want to set the sharing mode yourself, you'll have to use the msvcrt.open_osfhandle()
if you want to open files specifying a sharing mode.
There is a patch in the Python issue tracker that implements a sharing
module, illustrating how to do this. Just the opener from that patch, somewhat simplified, is:
import os
import msvcrt
import _winapi
CREATE_NEW = 1
CREATE_ALWAYS = 2
OPEN_EXISTING = 3
OPEN_ALWAYS = 4
TRUNCATE_EXISTING = 5
FILE_SHARE_READ = 0x00000001
FILE_SHARE_WRITE = 0x00000002
FILE_SHARE_DELETE = 0x00000004
FILE_SHARE_VALID_FLAGS = 0x00000007
FILE_ATTRIBUTE_READONLY = 0x00000001
FILE_ATTRIBUTE_NORMAL = 0x00000080
FILE_ATTRIBUTE_TEMPORARY = 0x00000100
FILE_FLAG_DELETE_ON_CLOSE = 0x04000000
FILE_FLAG_SEQUENTIAL_SCAN = 0x08000000
FILE_FLAG_RANDOM_ACCESS = 0x10000000
GENERIC_READ = 0x80000000
GENERIC_WRITE = 0x40000000
DELETE = 0x00010000
NULL = 0
_ACCESS_MASK = os.O_RDONLY | os.O_WRONLY | os.O_RDWR
_ACCESS_MAP = {os.O_RDONLY : GENERIC_READ,
os.O_WRONLY : GENERIC_WRITE,
os.O_RDWR : GENERIC_READ | GENERIC_WRITE}
_CREATE_MASK = os.O_CREAT | os.O_EXCL | os.O_TRUNC
_CREATE_MAP = {0 : OPEN_EXISTING,
os.O_EXCL : OPEN_EXISTING,
os.O_CREAT : OPEN_ALWAYS,
os.O_CREAT | os.O_EXCL : CREATE_NEW,
os.O_CREAT | os.O_TRUNC | os.O_EXCL : CREATE_NEW,
os.O_TRUNC : TRUNCATE_EXISTING,
os.O_TRUNC | os.O_EXCL : TRUNCATE_EXISTING,
os.O_CREAT | os.O_TRUNC : CREATE_ALWAYS}
def os_open(file, flags, mode=0o777,
*, share_flags=FILE_SHARE_VALID_FLAGS):
'''
Replacement for os.open() allowing moving or unlinking before closing
'''
if not isinstance(flags, int) and mode >= 0:
raise ValueError('bad flags: %r' % flags)
if not isinstance(mode, int) and mode >= 0:
raise ValueError('bad mode: %r' % mode)
if share_flags & ~FILE_SHARE_VALID_FLAGS:
raise ValueError('bad share_flags: %r' % share_flags)
access_flags = _ACCESS_MAP[flags & _ACCESS_MASK]
create_flags = _CREATE_MAP[flags & _CREATE_MASK]
attrib_flags = FILE_ATTRIBUTE_NORMAL
if flags & os.O_CREAT and mode & ~0o444 == 0:
attrib_flags = FILE_ATTRIBUTE_READONLY
if flags & os.O_TEMPORARY:
share_flags |= FILE_SHARE_DELETE
attrib_flags |= FILE_FLAG_DELETE_ON_CLOSE
access_flags |= DELETE
if flags & os.O_SHORT_LIVED:
attrib_flags |= FILE_ATTRIBUTE_TEMPORARY
if flags & os.O_SEQUENTIAL:
attrib_flags |= FILE_FLAG_SEQUENTIAL_SCAN
if flags & os.O_RANDOM:
attrib_flags |= FILE_FLAG_RANDOM_ACCESS
h = _winapi.CreateFile(file, access_flags, share_flags, NULL,
create_flags, attrib_flags, NULL)
return msvcrt.open_osfhandle(h, flags | os.O_NOINHERIT)