Python tạo tệp từ biến

File Names, Command Line Arguments, and Environment Variables

In Python, file names, command line arguments, and environment variables are represented using the string type. On some systems, decoding these strings to and from bytes is necessary before passing them to the operating system. Python uses the to perform this conversion (see )

The are configured at Python startup by the

>>> import os
>>> statinfo = os.stat('somefile.txt')
>>> statinfo
os.stat_result(st_mode=33188, st_ino=7876932, st_dev=234881026,
st_nlink=1, st_uid=501, st_gid=501, st_size=264, st_atime=1297230295,
st_mtime=1297230027, st_ctime=1297230027)
>>> statinfo.st_size
264

Changed in version 3. 1. On some systems, conversion using the file system encoding may fail. In this case, Python uses the , which means that undecodable bytes are replaced by a Unicode character U+DCxx on decoding, and these are again translated to the original byte on encoding.

The must guarantee to successfully decode all bytes below 128. If the file system encoding fails to provide this guarantee, API functions can raise

See also the

Python UTF-8 Mode

New in version 3. 7. See PEP 540 for more details.

The Python UTF-8 Mode ignores the and forces the usage of the UTF-8 encoding

• Use UTF-8 as the

• trả về

  >>> import os
  >>> statinfo = os.stat('somefile.txt')
  >>> statinfo
  os.stat_result(st_mode=33188, st_ino=7876932, st_dev=234881026,
  st_nlink=1, st_uid=501, st_gid=501, st_size=264, st_atime=1297230295,
  st_mtime=1297230027, st_ctime=1297230027)
  >>> statinfo.st_size
  264
  

  8

• returns

  >>> import os
  >>> statinfo = os.stat('somefile.txt')
  >>> statinfo
  os.stat_result(st_mode=33188, st_ino=7876932, st_dev=234881026,
  st_nlink=1, st_uid=501, st_gid=501, st_size=264, st_atime=1297230295,
  st_mtime=1297230027, st_ctime=1297230027)
  >>> statinfo.st_size
  264
  

  8 (the do_setlocale argument has no effect)

• , , and all use UTF-8 as their text encoding, with the

  os.stat in os.supports_dir_fd
  

  4 being enabled for and ( continues to use

  os.stat in os.supports_dir_fd
  

  8 as it does in the default locale-aware mode)

• On Unix, returns

  >>> import os
  >>> statinfo = os.stat('somefile.txt')
  >>> statinfo
  os.stat_result(st_mode=33188, st_ino=7876932, st_dev=234881026,
  st_nlink=1, st_uid=501, st_gid=501, st_size=264, st_atime=1297230295,
  st_mtime=1297230027, st_ctime=1297230027)
  >>> statinfo.st_size
  264
  

  8 rather than the device encoding

Lưu ý rằng cài đặt luồng tiêu chuẩn ở chế độ UTF-8 có thể bị ghi đè bởi (giống như chúng có thể ở chế độ nhận biết ngôn ngữ mặc định)

As a consequence of the changes in those lower level APIs, other higher level APIs also exhibit different default behaviours

• Command line arguments, environment variables and filenames are decoded to text using the UTF-8 encoding

• and use the UTF-8 encoding

• , , and use the UTF-8 encoding by default. However, they still use the strict error handler by default so that attempting to open a binary file in text mode is likely to raise an exception rather than producing nonsense data

The is enabled if the LC_CTYPE locale is

os.access in os.supports_effective_ids

os.access in os.supports_effective_ids

>>> import os
>>> statinfo = os.stat('somefile.txt')
>>> statinfo
os.stat_result(st_mode=33188, st_ino=7876932, st_dev=234881026,
st_nlink=1, st_uid=501, st_gid=501, st_size=264, st_atime=1297230295,
st_mtime=1297230027, st_ctime=1297230027)
>>> statinfo.st_size
264

It can be enabled or disabled using the command line option and the environment variable

If the environment variable is not set at all, then the interpreter defaults to using the current locale settings, unless the current locale is identified as a legacy ASCII-based locale (as described for ), and locale coercion is either disabled or fails. In such legacy locales, the interpreter will default to enabling UTF-8 mode unless explicitly instructed not to do so

The Python UTF-8 Mode can only be enabled at the Python startup. Its value can be read from

See also the and the

See also

Python 3. 15 will make default

Process Parameters

These functions and data items provide information and operate on the current process and user

Return the filename corresponding to the controlling terminal of the process

Unix, not Emscripten, not WASI

A object where keys and values are strings that represent the process environment. For example,

os.chdir in os.supports_fd

os.chdir in os.supports_fd

This mapping is captured the first time the module is imported, typically during Python startup as part of processing

os.chdir in os.supports_fd

This mapping may be used to modify the environment as well as query the environment. will be called automatically when the mapping is modified

On Unix, keys and values use and

os.stat in os.supports_follow_symlinks

Ghi chú

Calling directly does not change , so it’s better to modify

Ghi chú

On some platforms, including FreeBSD and macOS, setting

os.stat in os.supports_follow_symlinks

os.stat in os.supports_follow_symlinks

You can delete items in this mapping to unset environment variables. will be called automatically when an item is deleted from , and when one of the

import os
from os.path import join, getsize
for root, dirs, files in os.walk('python/Lib/email'):
    print(root, "consumes", end=" ")
    print(sum(getsize(join(root, name)) for name in files), end=" ")
    print("bytes in", len(files), "non-directory files")
    if 'CVS' in dirs:
        dirs.remove('CVS')  # don't visit CVS directories

import os
from os.path import join, getsize
for root, dirs, files in os.walk('python/Lib/email'):
    print(root, "consumes", end=" ")
    print(sum(getsize(join(root, name)) for name in files), end=" ")
    print("bytes in", len(files), "non-directory files")
    if 'CVS' in dirs:
        dirs.remove('CVS')  # don't visit CVS directories

Changed in version 3. 9. Updated to support PEP 584’s merge (

import os
from os.path import join, getsize
for root, dirs, files in os.walk('python/Lib/email'):
    print(root, "consumes", end=" ")
    print(sum(getsize(join(root, name)) for name in files), end=" ")
    print("bytes in", len(files), "non-directory files")
    if 'CVS' in dirs:
        dirs.remove('CVS')  # don't visit CVS directories

import os
from os.path import join, getsize
for root, dirs, files in os.walk('python/Lib/email'):
    print(root, "consumes", end=" ")
    print(sum(getsize(join(root, name)) for name in files), end=" ")
    print("bytes in", len(files), "non-directory files")
    if 'CVS' in dirs:
        dirs.remove('CVS')  # don't visit CVS directories

Bytes version of . a object where both keys and values are objects representing the process environment. and are synchronized (modifying updates , and vice versa)

is only available if is

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

Mới trong phiên bản 3. 2

Changed in version 3. 9. Updated to support PEP 584’s merge (

import os
from os.path import join, getsize
for root, dirs, files in os.walk('python/Lib/email'):
    print(root, "consumes", end=" ")
    print(sum(getsize(join(root, name)) for name in files), end=" ")
    print("bytes in", len(files), "non-directory files")
    if 'CVS' in dirs:
        dirs.remove('CVS')  # don't visit CVS directories

import os
from os.path import join, getsize
for root, dirs, files in os.walk('python/Lib/email'):
    print(root, "consumes", end=" ")
    print(sum(getsize(join(root, name)) for name in files), end=" ")
    print("bytes in", len(files), "non-directory files")
    if 'CVS' in dirs:
        dirs.remove('CVS')  # don't visit CVS directories

Các chức năng này được mô tả trong

Mã hóa tên tệp thành ;

là hàm ngược

Mới trong phiên bản 3. 2

Đã thay đổi trong phiên bản 3. 6. Hỗ trợ được thêm vào để chấp nhận các đối tượng triển khai giao diện.

Giải mã tên tệp từ ;

là hàm ngược

Mới trong phiên bản 3. 2

Đã thay đổi trong phiên bản 3. 6. Hỗ trợ được thêm vào để chấp nhận các đối tượng triển khai giao diện.

Trả về biểu diễn hệ thống tệp của đường dẫn

If or is passed in, it is returned unchanged. Otherwise is called and its value is returned as long as it is a or object. In all other cases, is raised

New in version 3. 6

An for objects representing a file system path, e. g.

New in version 3. 6

Return the file system path representation of the object

The method should only return a or object, with the preference being for

Return the value of the environment variable key as a string if it exists, or default if it doesn’t. key is a string. Note that since uses , the mapping of is similarly also captured on import, and the function may not reflect future environment changes

On Unix, keys and values are decoded with and

os.stat in os.supports_follow_symlinks

Unix, Windows

Return the value of the environment variable key as bytes if it exists, or default if it doesn’t. key must be bytes. Note that since uses , the mapping of is similarly also captured on import, and the function may not reflect future environment changes

is only available if is

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

Unix

Mới trong phiên bản 3. 2

Returns the list of directories that will be searched for a named executable, similar to a shell, when launching a process. env, when specified, should be an environment variable dictionary to lookup the PATH in. By default, when env is

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

Mới trong phiên bản 3. 2

Return the effective group id of the current process. This corresponds to the “set id” bit on the file being executed in the current process

Unix, not Emscripten, not WASI

Return the current process’s effective user id

Unix, not Emscripten, not WASI

Return the real group id of the current process

Unix

The function is a stub on Emscripten and WASI, see for more information

Return list of group ids that user belongs to. If group is not in the list, it is included; typically, group is specified as the group ID field from the password record for user, because that group ID will otherwise be potentially omitted

Unix, not Emscripten, not WASI

New in version 3. 3

Return list of supplemental group ids associated with the current process

Unix, not Emscripten, not WASI

Ghi chú

On macOS, behavior differs somewhat from other Unix platforms. If the Python interpreter was built with a deployment target of

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

Return the name of the user logged in on the controlling terminal of the process. For most purposes, it is more useful to use since the latter checks the environment variables

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

Unix, Windows, not Emscripten, not WASI

Return the process group id of the process with process id pid. If pid is 0, the process group id of the current process is returned

Unix, not Emscripten, not WASI

Return the id of the current process group

Unix, not Emscripten, not WASI

Return the current process id

The function is a stub on Emscripten and WASI, see for more information

Return the parent’s process id. When the parent process has exited, on Unix the id returned is the one of the init process (1), on Windows it is still the same id, which may be already reused by another process

Unix, Windows, not Emscripten, not WASI

Changed in version 3. 2. Added support for Windows.

Get program scheduling priority. The value which is one of , , or , and who is interpreted relative to which (a process identifier for , process group identifier for , and a user ID for ). A zero value for who denotes (respectively) the calling process, the process group of the calling process, or the real user ID of the calling process

Unix, not Emscripten, not WASI

New in version 3. 3

Parameters for the and functions

Unix, not Emscripten, not WASI

New in version 3. 3

Return a tuple (ruid, euid, suid) denoting the current process’s real, effective, and saved user ids

Unix, not Emscripten, not WASI

Mới trong phiên bản 3. 2

Return a tuple (rgid, egid, sgid) denoting the current process’s real, effective, and saved group ids

Unix, not Emscripten, not WASI

Mới trong phiên bản 3. 2

Return the current process’s real user id

Unix

The function is a stub on Emscripten and WASI, see for more information

Call the system initgroups() to initialize the group access list with all of the groups of which the specified username is a member, plus the specified group id

Unix, not Emscripten, not WASI

Mới trong phiên bản 3. 2

Set the environment variable named key to the string value. Such changes to the environment affect subprocesses started with , or and

Assignments to items in are automatically translated into corresponding calls to ; however, calls to don’t update , so it is actually preferable to assign to items of . This also applies to and , which respectively use and in their implementations

Ghi chú

On some platforms, including FreeBSD and macOS, setting

os.stat in os.supports_follow_symlinks

os.stat in os.supports_follow_symlinks

Raises an

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

Changed in version 3. 9. The function is now always available.

Set the current process’s effective group id

Unix, not Emscripten, not WASI

Set the current process’s effective user id

Unix, not Emscripten, not WASI

Set the current process’ group id

Unix, not Emscripten, not WASI

Set the list of supplemental group ids associated with the current process to groups. groups must be a sequence, and each element must be an integer identifying a group. This operation is typically available only to the superuser

Unix, not Emscripten, not WASI

Ghi chú

On macOS, the length of groups may not exceed the system-defined maximum number of effective group ids, typically 16. See the documentation for for cases where it may not return the same group list set by calling setgroups()

Call the system call

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

Unix, not Emscripten, not WASI

Call the system call

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

Unix, not Emscripten, not WASI

Set program scheduling priority. The value which is one of , , or , and who is interpreted relative to which (a process identifier for , process group identifier for , and a user ID for ). A zero value for who denotes (respectively) the calling process, the process group of the calling process, or the real user ID of the calling process. priority is a value in the range -20 to 19. The default priority is 0; lower priorities cause more favorable scheduling

Unix, not Emscripten, not WASI

New in version 3. 3

Set the current process’s real and effective group ids

Unix, not Emscripten, not WASI

Set the current process’s real, effective, and saved group ids

Unix, not Emscripten, not WASI

Mới trong phiên bản 3. 2

Đặt id người dùng thực, hiệu quả và đã lưu của quy trình hiện tại

Unix, not Emscripten, not WASI

Mới trong phiên bản 3. 2

Set the current process’s real and effective user ids

Unix, not Emscripten, not WASI

Call the system call

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

Unix, not Emscripten, not WASI

Call the system call

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

Unix, not Emscripten, not WASI

Set the current process’s user id

Unix, not Emscripten, not WASI

Return the error message corresponding to the error code in code. On platforms where

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

Mới trong phiên bản 3. 2

Set the current numeric umask and return the previous umask

The function is a stub on Emscripten and WASI, see for more information

Returns information identifying the current operating system. The return value is an object with five attributes

• if os.access("myfile", os.R_OK):
      with open("myfile") as fp:
          return fp.read()
  return "some default data"
  

  93 - operating system name

• if os.access("myfile", os.R_OK):
      with open("myfile") as fp:
          return fp.read()
  return "some default data"
  

  94 - name of machine on network (implementation-defined)

• if os.access("myfile", os.R_OK):
      with open("myfile") as fp:
          return fp.read()
  return "some default data"
  

  95 - operating system release

• if os.access("myfile", os.R_OK):
      with open("myfile") as fp:
          return fp.read()
  return "some default data"
  

  96 - operating system version

• if os.access("myfile", os.R_OK):
      with open("myfile") as fp:
          return fp.read()
  return "some default data"
  

  97 - hardware identifier

For backwards compatibility, this object is also iterable, behaving like a five-tuple containing

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

Some systems truncate

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

Unix

Changed in version 3. 3. Return type changed from a tuple to a tuple-like object with named attributes.

Unset (delete) the environment variable named key. Such changes to the environment affect subprocesses started with , or and

Deletion of items in is automatically translated into a corresponding call to ; however, calls to don’t update , so it is actually preferable to delete items of

Raises an

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

Changed in version 3. 9. The function is now always available and is also available on Windows.

File Object Creation

These functions create new . (See also for opening file descriptors. )

Return an open file object connected to the file descriptor fd. This is an alias of the built-in function and accepts the same arguments. The only difference is that the first argument of must always be an integer

File Descriptor Operations

These functions operate on I/O streams referenced using file descriptors

File descriptors are small integers corresponding to a file that has been opened by the current process. For example, standard input is usually file descriptor 0, standard output is 1, and standard error is 2. Further files opened by a process will then be assigned 3, 4, 5, and so forth. The name “file descriptor” is slightly deceptive; on Unix platforms, sockets and pipes are also referenced by file descriptors

The method can be used to obtain the file descriptor associated with a when required. Note that using the file descriptor directly will bypass the file object methods, ignoring aspects such as internal buffering of data

Close file descriptor fd

Ghi chú

This function is intended for low-level I/O and must be applied to a file descriptor as returned by or . To close a “file object” returned by the built-in function or by or , use its method

Close all file descriptors from fd_low (inclusive) to fd_high (exclusive), ignoring errors. Equivalent to (but much faster than)

for fd in range(fd_low, fd_high):
    try:
        os.close(fd)
    except OSError:
        pass

Copy count bytes from file descriptor src, starting from offset offset_src, to file descriptor dst, starting from offset offset_dst. If offset_src is None, then src is read from the current position; respectively for offset_dst. The files pointed by src and dst must reside in the same filesystem, otherwise an is raised with set to

This copy is done without the additional cost of transferring data from the kernel to user space and then back into the kernel. Additionally, some filesystems could implement extra optimizations. The copy is done as if both files are opened as binary

The return value is the amount of bytes copied. This could be less than the amount requested

Linux >= 4. 5 with glibc >= 2. 27

New in version 3. 8

Return a string describing the encoding of the device associated with fd if it is connected to a terminal; else return

On Unix, if the is enabled, return

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

Changed in version 3. 10. On Unix, the function now implements the Python UTF-8 Mode.

Return a duplicate of file descriptor fd. Bộ mô tả tệp mới là

On Windows, when duplicating a standard stream (0. stdin, 1. stdout, 2. stderr), bộ mô tả tệp mới là

không phải WASI

Changed in version 3. 4. The new file descriptor is now non-inheritable.

Sao chép bộ mô tả tệp fd thành fd2, đóng cái sau trước nếu cần. Trả lại fd2. Bộ mô tả tệp mới theo mặc định hoặc không thể kế thừa nếu có thể kế thừa là

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

không phải WASI

Đã thay đổi trong phiên bản 3. 4. Thêm tham số kế thừa tùy chọn.

Đã thay đổi trong phiên bản 3. 7. Trả lại fd2 khi thành công. Trước đây,

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

Thay đổi chế độ của tệp do fd cung cấp thành chế độ số. Xem tài liệu để biết các giá trị có thể có của chế độ. Kể từ Python 3. 3, điều này tương đương với

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

Đưa ra một

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

Unix

Chức năng này bị giới hạn trên Emscripten và WASI, xem để biết thêm thông tin

Thay đổi chủ sở hữu và id nhóm của tệp do fd cung cấp thành uid và gid dạng số. Để giữ nguyên một trong các id, hãy đặt nó thành -1. Nhìn thấy. Kể từ Python 3. 3, điều này tương đương với

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

Nâng cao một

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

Unix

Chức năng này bị giới hạn trên Emscripten và WASI, xem để biết thêm thông tin

Buộc ghi tệp với filedescriptor fd vào đĩa. Không buộc cập nhật siêu dữ liệu

Unix

Ghi chú

Chức năng này không có trên MacOS

Return system configuration information relevant to an open file. name specifies the configuration value to retrieve; it may be a string which is the name of a defined system value; these names are specified in a number of standards (POSIX. 1, Unix 95, Unix 98, and others). Some platforms define additional names as well. The names known to the host operating system are given in the

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

If name is a string and is not known, is raised. If a specific value for name is not supported by the host system, even if it is included in

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

As of Python 3. 3, this is equivalent to

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

Unix

Get the status of the file descriptor fd. Return a object

As of Python 3. 3, this is equivalent to

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

See also

The function

Return information about the filesystem containing the file associated with file descriptor fd, like . Kể từ Python 3. 3, this is equivalent to

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

Unix

Force write of file with filedescriptor fd to disk. On Unix, this calls the native

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

If you’re starting with a buffered Python f, first do

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

Unix, Windows

Truncate the file corresponding to file descriptor fd, so that it is at most length bytes in size. As of Python 3. 3, this is equivalent to

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

Raises an

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

Unix, Windows

Changed in version 3. 5. Added support for Windows

Get the blocking mode of the file descriptor.

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

See also and

Unix

Chức năng này bị giới hạn trên Emscripten và WASI, xem để biết thêm thông tin

New in version 3. 5

Return

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

Apply, test or remove a POSIX lock on an open file descriptor. fd is an open file descriptor. cmd specifies the command to use - one of , , or . len specifies the section of the file to lock

Raises an

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

Unix

New in version 3. 3

Flags that specify what action will take

Unix

New in version 3. 3

Prepare the tty of which fd is a file descriptor for a new login session. Make the calling process a session leader; make the tty the controlling tty, the stdin, the stdout, and the stderr of the calling process; close fd

Unix, not Emscripten, not WASI

New in version 3. 11

Set the current position of file descriptor fd to position pos, modified by how. or

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

Parameters to the function. Giá trị của chúng lần lượt là 0, 1 và 2

New in version 3. 3. Một số hệ điều hành có thể hỗ trợ các giá trị bổ sung, như

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

Open the file path and set various flags according to flags and possibly its mode according to mode. When computing mode, the current umask value is first masked out. Return the file descriptor for the newly opened file. The new file descriptor is

For a description of the flag and mode values, see the C run-time documentation; flag constants (like and ) are defined in the module. In particular, on Windows adding is needed to open files in binary mode

This function can support with the dir_fd parameter

Raises an

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

Changed in version 3. 4. The new file descriptor is now non-inheritable.

Ghi chú

This function is intended for low-level I/O. For normal usage, use the built-in function , which returns a with

with os.scandir(path) as it:
    for entry in it:
        if not entry.name.startswith('.') and entry.is_file():
            print(entry.name)

with os.scandir(path) as it:
    for entry in it:
        if not entry.name.startswith('.') and entry.is_file():
            print(entry.name)

New in version 3. 3. The dir_fd argument.

Changed in version 3. 5. If the system call is interrupted and the signal handler does not raise an exception, the function now retries the system call instead of raising an exception (see PEP 475 for the rationale).

Changed in version 3. 6. Accepts a .

The following constants are options for the flags parameter to the function. They can be combined using the bitwise OR operator

import os
from os.path import join, getsize
for root, dirs, files in os.walk('python/Lib/email'):
    print(root, "consumes", end=" ")
    print(sum(getsize(join(root, name)) for name in files), end=" ")
    print("bytes in", len(files), "non-directory files")
    if 'CVS' in dirs:
        dirs.remove('CVS')  # don't visit CVS directories

The above constants are available on Unix and Windows

The above constants are only available on Unix

Changed in version 3. 3. Add constant.

The above constants are only available on Windows

The above constants are only available on macOS

Changed in version 3. 10. Add , , and constants.

The above constants are extensions and not present if they are not defined by the C library

Changed in version 3. 4. Add on systems that support it. Add , only available on Linux Kernel 3. 11 or newer.

Open a new pseudo-terminal pair. Return a pair of file descriptors

with os.scandir(path) as it:
    for entry in it:
        if not entry.name.startswith('.') and entry.is_file():
            print(entry.name)

Unix, not Emscripten, not WASI

Changed in version 3. 4. The new file descriptors are now non-inheritable.

Create a pipe. Return a pair of file descriptors

with os.scandir(path) as it:
    for entry in it:
        if not entry.name.startswith('.') and entry.is_file():
            print(entry.name)

Unix, Windows

Changed in version 3. 4. The new file descriptors are now non-inheritable.

Create a pipe with flags set atomically. flags can be constructed by ORing together one or more of these values. , . Return a pair of file descriptors

with os.scandir(path) as it:
    for entry in it:
        if not entry.name.startswith('.') and entry.is_file():
            print(entry.name)

Unix, not Emscripten, not WASI

New in version 3. 3

Ensures that enough disk space is allocated for the file specified by fd starting from offset and continuing for len bytes

Unix, not Emscripten

New in version 3. 3

Announces an intention to access data in a specific pattern thus allowing the kernel to make optimizations. The advice applies to the region of the file specified by fd starting at offset and continuing for len bytes. lời khuyên là một trong , , , , hoặc

Unix

New in version 3. 3

Các cờ có thể được sử dụng trong lời khuyên chỉ định mẫu truy cập có khả năng được sử dụng

Unix

New in version 3. 3

Đọc tối đa n byte từ bộ mô tả tệp fd tại vị trí bù trừ, giữ nguyên độ lệch tệp

Trả về một chuỗi byte chứa các byte đã đọc. Nếu đã đến cuối tệp được tham chiếu bởi fd, một đối tượng byte trống sẽ được trả về

Unix

New in version 3. 3

Đọc từ bộ mô tả tệp fd ở vị trí bù vào bộ đệm có thể thay đổi, giữ nguyên phần bù tệp. Truyền dữ liệu vào từng bộ đệm cho đến khi đầy và sau đó chuyển sang bộ đệm tiếp theo trong chuỗi để giữ phần dữ liệu còn lại

Đối số cờ chứa OR theo bit bằng 0 hoặc nhiều cờ sau

Trả về tổng số byte thực sự đọc có thể nhỏ hơn tổng dung lượng của tất cả các đối tượng

Hệ điều hành có thể đặt giới hạn (giá trị

with os.scandir(path) as it:
    for entry in it:
        if not entry.name.startswith('.') and entry.is_file():
            print(entry.name)

Combine the functionality of and

Linux >= 2. 6. 30, FreeBSD >= 6. 0, OpenBSD >= 2. 7, AIX >= 7. 1

Using flags requires Linux >= 4. 6

New in version 3. 7

Do not wait for data which is not immediately available. If this flag is specified, the system call will return instantly if it would have to read data from the backing storage or wait for a lock

If some data was successfully read, it will return the number of bytes read. If no bytes were read, it will return

with os.scandir(path) as it:
    for entry in it:
        if not entry.name.startswith('.') and entry.is_file():
            print(entry.name)

Linux >= 4. 14

New in version 3. 7

High priority read/write. Allows block-based filesystems to use polling of the device, which provides lower latency, but may use additional resources

Currently, on Linux, this feature is usable only on a file descriptor opened using the flag

Linux >= 4. 6

New in version 3. 7

Write the bytestring in str to file descriptor fd at position of offset, leaving the file offset unchanged

Return the number of bytes actually written

Unix

New in version 3. 3

Write the buffers contents to file descriptor fd at a offset offset, leaving the file offset unchanged. buffers must be a sequence of . Buffers are processed in array order. Entire contents of the first buffer is written before proceeding to the second, and so on

Đối số cờ chứa OR theo bit bằng 0 hoặc nhiều cờ sau

Return the total number of bytes actually written

Hệ điều hành có thể đặt giới hạn (giá trị

with os.scandir(path) as it:
    for entry in it:
        if not entry.name.startswith('.') and entry.is_file():
            print(entry.name)

Combine the functionality of and

Linux >= 2. 6. 30, FreeBSD >= 6. 0, OpenBSD >= 2. 7, AIX >= 7. 1

Using flags requires Linux >= 4. 6

New in version 3. 7

Provide a per-write equivalent of the flag. This flag effect applies only to the data range written by the system call

Linux >= 4. 7

New in version 3. 7

Provide a per-write equivalent of the flag. This flag effect applies only to the data range written by the system call

Linux >= 4. 7

New in version 3. 7

Provide a per-write equivalent of the flag. This flag is meaningful only for , and its effect applies only to the data range written by the system call. The offset argument does not affect the write operation; the data is always appended to the end of the file. However, if the offset argument is

with os.scandir(path) as it:
    for entry in it:
        if not entry.name.startswith('.') and entry.is_file():
            print(entry.name)

Linux >= 4. 16

New in version 3. 10

Read at most n bytes from file descriptor fd

Trả về một chuỗi byte chứa các byte đã đọc. Nếu đã đến cuối tệp được tham chiếu bởi fd, một đối tượng byte trống sẽ được trả về

Ghi chú

This function is intended for low-level I/O and must be applied to a file descriptor as returned by or . To read a “file object” returned by the built-in function or by or , or , use its

with os.scandir(path) as it:
    for entry in it:
        if not entry.name.startswith('.') and entry.is_file():
            print(entry.name)

with os.scandir(path) as it:
    for entry in it:
        if not entry.name.startswith('.') and entry.is_file():
            print(entry.name)

Changed in version 3. 5. If the system call is interrupted and the signal handler does not raise an exception, the function now retries the system call instead of raising an exception (see PEP 475 for the rationale).

Copy count bytes from file descriptor in_fd to file descriptor out_fd starting at offset. Return the number of bytes sent. When EOF is reached return

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

The first function notation is supported by all platforms that define

On Linux, if offset is given as

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

The second case may be used on macOS and FreeBSD where headers and trailers are arbitrary sequences of buffers that are written before and after the data from in_fd is written. It returns the same as the first case

On macOS and FreeBSD, a value of

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

All platforms support sockets as out_fd file descriptor, and some platforms allow other types (e. g. regular file, pipe) as well

Cross-platform applications should not use headers, trailers and flags arguments

Unix, not Emscripten, not WASI

Ghi chú

For a higher-level wrapper of , see

New in version 3. 3

Changed in version 3. 9. Parameters out and in was renamed to out_fd and in_fd.

Set the blocking mode of the specified file descriptor. Set the flag if blocking is

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

See also and

Unix

Chức năng này bị giới hạn trên Emscripten và WASI, xem để biết thêm thông tin

New in version 3. 5

Parameters to the function, if the implementation supports them

Unix, not Emscripten, not WASI

New in version 3. 3

Parameter to the function, if the implementation supports it. The data won’t be cached in the virtual memory and will be freed afterwards

Unix, not Emscripten, not WASI

New in version 3. 11

Transfer count bytes from file descriptor src, starting from offset offset_src, to file descriptor dst, starting from offset offset_dst. At least one of the file descriptors must refer to a pipe. If offset_src is None, then src is read from the current position; respectively for offset_dst. The offset associated to the file descriptor that refers to a pipe must be

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

This copy is done without the additional cost of transferring data from the kernel to user space and then back into the kernel. Additionally, some filesystems could implement extra optimizations. The copy is done as if both files are opened as binary

Upon successful completion, returns the number of bytes spliced to or from the pipe. A return value of 0 means end of input. If src refers to a pipe, then this means that there was no data to transfer, and it would not make sense to block because there are no writers connected to the write end of the pipe

Linux >= 2. 6. 17 with glibc >= 2. 5

New in version 3. 10

New in version 3. 10

Read from a file descriptor fd into a number of mutable buffers. Transfer data into each buffer until it is full and then move on to the next buffer in the sequence to hold the rest of the data

Trả về tổng số byte thực sự đọc có thể nhỏ hơn tổng dung lượng của tất cả các đối tượng

Hệ điều hành có thể đặt giới hạn (giá trị

with os.scandir(path) as it:
    for entry in it:
        if not entry.name.startswith('.') and entry.is_file():
            print(entry.name)

Unix

New in version 3. 3

Return the process group associated with the terminal given by fd (an open file descriptor as returned by )

Unix, not WASI

Set the process group associated with the terminal given by fd (an open file descriptor as returned by ) to pg

Unix, not WASI

Return a string which specifies the terminal device associated with file descriptor fd. If fd is not associated with a terminal device, an exception is raised

Unix

Write the bytestring in str to file descriptor fd

Return the number of bytes actually written

Ghi chú

This function is intended for low-level I/O and must be applied to a file descriptor as returned by or . To write a “file object” returned by the built-in function or by or , or or , use its

with os.scandir(path) as it:
    for entry in it:
        if not entry.name.startswith('.') and entry.is_file():
            print(entry.name)

Changed in version 3. 5. If the system call is interrupted and the signal handler does not raise an exception, the function now retries the system call instead of raising an exception (see PEP 475 for the rationale).

Write the contents of buffers to file descriptor fd. buffers must be a sequence of . Buffers are processed in array order. Entire contents of the first buffer is written before proceeding to the second, and so on

Returns the total number of bytes actually written

Hệ điều hành có thể đặt giới hạn (giá trị

with os.scandir(path) as it:
    for entry in it:
        if not entry.name.startswith('.') and entry.is_file():
            print(entry.name)

Unix

New in version 3. 3

with os.scandir(path) as it:
    for entry in it:
        if not entry.name.startswith('.') and entry.is_file():
            print(entry.name)

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

with os.scandir(path) as it:
    for entry in it:
        if not entry.name.startswith('.') and entry.is_file():
            print(entry.name)

with os.scandir(path) as it:
    for entry in it:
        if not entry.name.startswith('.') and entry.is_file():
            print(entry.name)

with os.scandir(path) as it:
    for entry in it:
        if not entry.name.startswith('.') and entry.is_file():
            print(entry.name)

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

Files and Directories

On some Unix platforms, many of these functions support one or more of these features

• specifying a file descriptor. Normally the path argument provided to functions in the module must be a string specifying a file path. However, some functions now alternatively accept an open file descriptor for their path argument. The function will then operate on the file referred to by the descriptor. (For POSIX systems, Python will call the variant of the function prefixed with

  >>> import os
  >>> statinfo = os.stat('somefile.txt')
  >>> statinfo
  os.stat_result(st_mode=33188, st_ino=7876932, st_dev=234881026,
  st_nlink=1, st_uid=501, st_gid=501, st_size=264, st_atime=1297230295,
  st_mtime=1297230027, st_ctime=1297230027)
  >>> statinfo.st_size
  264
  

  04 (e. g. call

  >>> import os
  >>> statinfo = os.stat('somefile.txt')
  >>> statinfo
  os.stat_result(st_mode=33188, st_ino=7876932, st_dev=234881026,
  st_nlink=1, st_uid=501, st_gid=501, st_size=264, st_atime=1297230295,
  st_mtime=1297230027, st_ctime=1297230027)
  >>> statinfo.st_size
  264
  

  05 instead of

  >>> import os
  >>> statinfo = os.stat('somefile.txt')
  >>> statinfo
  os.stat_result(st_mode=33188, st_ino=7876932, st_dev=234881026,
  st_nlink=1, st_uid=501, st_gid=501, st_size=264, st_atime=1297230295,
  st_mtime=1297230027, st_ctime=1297230027)
  >>> statinfo.st_size
  264
  

  06). )

  You can check whether or not path can be specified as a file descriptor for a particular function on your platform using . If this functionality is unavailable, using it will raise a

  If the function also supports dir_fd or follow_symlinks arguments, it’s an error to specify one of those when supplying path as a file descriptor

• paths relative to directory descriptors. If dir_fd is not

  if os.access("myfile", os.R_OK):
      with open("myfile") as fp:
          return fp.read()
  return "some default data"
  

  35, it should be a file descriptor referring to a directory, and the path to operate on should be relative; path will then be relative to that directory. If the path is absolute, dir_fd is ignored. (For POSIX systems, Python will call the variant of the function with an

  >>> import os
  >>> statinfo = os.stat('somefile.txt')
  >>> statinfo
  os.stat_result(st_mode=33188, st_ino=7876932, st_dev=234881026,
  st_nlink=1, st_uid=501, st_gid=501, st_size=264, st_atime=1297230295,
  st_mtime=1297230027, st_ctime=1297230027)
  >>> statinfo.st_size
  264
  

  10 suffix and possibly prefixed with

  >>> import os
  >>> statinfo = os.stat('somefile.txt')
  >>> statinfo
  os.stat_result(st_mode=33188, st_ino=7876932, st_dev=234881026,
  st_nlink=1, st_uid=501, st_gid=501, st_size=264, st_atime=1297230295,
  st_mtime=1297230027, st_ctime=1297230027)
  >>> statinfo.st_size
  264
  

  04 (e. g. call

  >>> import os
  >>> statinfo = os.stat('somefile.txt')
  >>> statinfo
  os.stat_result(st_mode=33188, st_ino=7876932, st_dev=234881026,
  st_nlink=1, st_uid=501, st_gid=501, st_size=264, st_atime=1297230295,
  st_mtime=1297230027, st_ctime=1297230027)
  >>> statinfo.st_size
  264
  

  12 instead of

  >>> import os
  >>> statinfo = os.stat('somefile.txt')
  >>> statinfo
  os.stat_result(st_mode=33188, st_ino=7876932, st_dev=234881026,
  st_nlink=1, st_uid=501, st_gid=501, st_size=264, st_atime=1297230295,
  st_mtime=1297230027, st_ctime=1297230027)
  >>> statinfo.st_size
  264
  

  13)

  You can check whether or not dir_fd is supported for a particular function on your platform using . If it’s unavailable, using it will raise a

• not following symlinks. If follow_symlinks is

  if os.access("myfile", os.R_OK):
      with open("myfile") as fp:
          return fp.read()
  return "some default data"
  

  92, and the last element of the path to operate on is a symbolic link, the function will operate on the symbolic link itself rather than the file pointed to by the link. (For POSIX systems, Python will call the

  >>> import os
  >>> statinfo = os.stat('somefile.txt')
  >>> statinfo
  os.stat_result(st_mode=33188, st_ino=7876932, st_dev=234881026,
  st_nlink=1, st_uid=501, st_gid=501, st_size=264, st_atime=1297230295,
  st_mtime=1297230027, st_ctime=1297230027)
  >>> statinfo.st_size
  264
  

  17 variant of the function. )

  You can check whether or not follow_symlinks is supported for a particular function on your platform using . If it’s unavailable, using it will raise a

Use the real uid/gid to test for access to path. Note that most operations will use the effective uid/gid, therefore this routine can be used in a suid/sgid environment to test if the invoking user has the specified access to path. mode should be to test the existence of path, or it can be the inclusive OR of one or more of , , and to test permissions. Return if access is allowed, if not. See the Unix man page access(2) for more information

Chức năng này có thể hỗ trợ xác định và

If effective_ids is

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

Ghi chú

Sử dụng để kiểm tra xem người dùng có được phép sử dụng e. g. mở một tệp trước khi thực sự làm như vậy bằng cách sử dụng sẽ tạo ra một lỗ hổng bảo mật, bởi vì người dùng có thể lợi dụng khoảng thời gian ngắn giữa việc kiểm tra và mở tệp để thao tác với nó. Tốt hơn là sử dụng các kỹ thuật. Ví dụ

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

được viết tốt hơn như

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

Ghi chú

Các hoạt động I/O có thể không thành công ngay cả khi được chỉ ra rằng chúng sẽ thành công, đặc biệt đối với các hoạt động trên hệ thống tệp mạng có thể có ngữ nghĩa quyền vượt ra ngoài mô hình bit quyền POSIX thông thường

Đã thay đổi trong phiên bản 3. 3. Đã thêm các tham số dir_fd, effect_ids và follow_symlinks.

Changed in version 3. 6. Accepts a .

Values to pass as the mode parameter of to test the existence, readability, writability and executability of path, respectively

Change the current working directory to path

This function can support . The descriptor must refer to an opened directory, not an open file

This function can raise and subclasses such as , , and

Raises an

>>> import os
>>> statinfo = os.stat('somefile.txt')
>>> statinfo
os.stat_result(st_mode=33188, st_ino=7876932, st_dev=234881026,
st_nlink=1, st_uid=501, st_gid=501, st_size=264, st_atime=1297230295,
st_mtime=1297230027, st_ctime=1297230027)
>>> statinfo.st_size
264

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

New in version 3. 3. Added support for specifying path as a file descriptor on some platforms.

Changed in version 3. 6. Accepts a .

Set the flags of path to the numeric flags. flags may take a combination (bitwise OR) of the following values (as defined in the module)

This function can support

Raises an

>>> import os
>>> statinfo = os.stat('somefile.txt')
>>> statinfo
os.stat_result(st_mode=33188, st_ino=7876932, st_dev=234881026,
st_nlink=1, st_uid=501, st_gid=501, st_size=264, st_atime=1297230295,
st_mtime=1297230027, st_ctime=1297230027)
>>> statinfo.st_size
264

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

Unix, not Emscripten, not WASI

New in version 3. 3. The follow_symlinks argument.

Changed in version 3. 6. Accepts a .

Change the mode of path to the numeric mode. mode may take one of the following values (as defined in the module) or bitwise ORed combinations of them

This function can support , and

Ghi chú

Although Windows supports , you can only set the file’s read-only flag with it (via the

>>> import os
>>> statinfo = os.stat('somefile.txt')
>>> statinfo
os.stat_result(st_mode=33188, st_ino=7876932, st_dev=234881026,
st_nlink=1, st_uid=501, st_gid=501, st_size=264, st_atime=1297230295,
st_mtime=1297230027, st_ctime=1297230027)
>>> statinfo.st_size
264

>>> import os
>>> statinfo = os.stat('somefile.txt')
>>> statinfo
os.stat_result(st_mode=33188, st_ino=7876932, st_dev=234881026,
st_nlink=1, st_uid=501, st_gid=501, st_size=264, st_atime=1297230295,
st_mtime=1297230027, st_ctime=1297230027)
>>> statinfo.st_size
264

Chức năng này bị giới hạn trên Emscripten và WASI, xem để biết thêm thông tin

Đưa ra một

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

New in version 3. 3. Added support for specifying path as an open file descriptor, and the dir_fd and follow_symlinks arguments.

Changed in version 3. 6. Accepts a .

Change the owner and group id of path to the numeric uid and gid. To leave one of the ids unchanged, set it to -1

This function can support , and

Xem chức năng cấp cao hơn chấp nhận tên ngoài id số

Nâng cao một

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

Unix

Chức năng này bị giới hạn trên Emscripten và WASI, xem để biết thêm thông tin

New in version 3. 3. Added support for specifying path as an open file descriptor, and the dir_fd and follow_symlinks arguments.

Changed in version 3. 6. Supports a .

Change the root directory of the current process to path

Unix, not Emscripten, not WASI

Changed in version 3. 6. Accepts a .

Change the current working directory to the directory represented by the file descriptor fd. The descriptor must refer to an opened directory, not an open file. As of Python 3. 3, this is equivalent to

>>> import os
>>> statinfo = os.stat('somefile.txt')
>>> statinfo
os.stat_result(st_mode=33188, st_ino=7876932, st_dev=234881026,
st_nlink=1, st_uid=501, st_gid=501, st_size=264, st_atime=1297230295,
st_mtime=1297230027, st_ctime=1297230027)
>>> statinfo.st_size
264

Raises an

>>> import os
>>> statinfo = os.stat('somefile.txt')
>>> statinfo
os.stat_result(st_mode=33188, st_ino=7876932, st_dev=234881026,
st_nlink=1, st_uid=501, st_gid=501, st_size=264, st_atime=1297230295,
st_mtime=1297230027, st_ctime=1297230027)
>>> statinfo.st_size
264

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

Unix

Return a string representing the current working directory

Return a bytestring representing the current working directory

Changed in version 3. 8. The function now uses the UTF-8 encoding on Windows, rather than the ANSI code page. see PEP 529 for the rationale. The function is no longer deprecated on Windows.

Set the flags of path to the numeric flags, like , but do not follow symbolic links. As of Python 3. 3, this is equivalent to

>>> import os
>>> statinfo = os.stat('somefile.txt')
>>> statinfo
os.stat_result(st_mode=33188, st_ino=7876932, st_dev=234881026,
st_nlink=1, st_uid=501, st_gid=501, st_size=264, st_atime=1297230295,
st_mtime=1297230027, st_ctime=1297230027)
>>> statinfo.st_size
264

Raises an

>>> import os
>>> statinfo = os.stat('somefile.txt')
>>> statinfo
os.stat_result(st_mode=33188, st_ino=7876932, st_dev=234881026,
st_nlink=1, st_uid=501, st_gid=501, st_size=264, st_atime=1297230295,
st_mtime=1297230027, st_ctime=1297230027)
>>> statinfo.st_size
264

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

Unix, not Emscripten, not WASI

Changed in version 3. 6. Accepts a .

Change the mode of path to the numeric mode. If path is a symlink, this affects the symlink rather than the target. See the docs for for possible values of mode. As of Python 3. 3, this is equivalent to

>>> import os
>>> statinfo = os.stat('somefile.txt')
>>> statinfo
os.stat_result(st_mode=33188, st_ino=7876932, st_dev=234881026,
st_nlink=1, st_uid=501, st_gid=501, st_size=264, st_atime=1297230295,
st_mtime=1297230027, st_ctime=1297230027)
>>> statinfo.st_size
264

Đưa ra một

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

Unix

Changed in version 3. 6. Accepts a .

Change the owner and group id of path to the numeric uid and gid. This function will not follow symbolic links. As of Python 3. 3, this is equivalent to

os.stat in os.supports_dir_fd

Nâng cao một

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

Unix

Changed in version 3. 6. Accepts a .

Create a hard link pointing to src named dst

This function can support specifying src_dir_fd and/or dst_dir_fd to supply , and

Raises an

os.stat in os.supports_dir_fd

os.stat in os.supports_dir_fd

os.stat in os.supports_dir_fd

os.stat in os.supports_dir_fd

os.stat in os.supports_dir_fd

Unix, Windows

Changed in version 3. 2. Added Windows support.

New in version 3. 3. Added the src_dir_fd, dst_dir_fd, and follow_symlinks arguments.

Changed in version 3. 6. Accepts a for src and dst.

Return a list containing the names of the entries in the directory given by path. The list is in arbitrary order, and does not include the special entries

os.stat in os.supports_dir_fd

os.stat in os.supports_dir_fd

path may be a . If path is of type

import os
from os.path import join, getsize
for root, dirs, files in os.walk('python/Lib/email'):
    print(root, "consumes", end=" ")
    print(sum(getsize(join(root, name)) for name in files), end=" ")
    print("bytes in", len(files), "non-directory files")
    if 'CVS' in dirs:
        dirs.remove('CVS')  # don't visit CVS directories

import os
from os.path import join, getsize
for root, dirs, files in os.walk('python/Lib/email'):
    print(root, "consumes", end=" ")
    print(sum(getsize(join(root, name)) for name in files), end=" ")
    print("bytes in", len(files), "non-directory files")
    if 'CVS' in dirs:
        dirs.remove('CVS')  # don't visit CVS directories

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

This function can also support ; the file descriptor must refer to a directory

Raises an

os.stat in os.supports_dir_fd

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

Ghi chú

To encode

if os.access("myfile", os.R_OK):
    with open("myfile") as fp:
        return fp.read()
return "some default data"

import os
from os.path import join, getsize
for root, dirs, files in os.walk('python/Lib/email'):
    print(root, "consumes", end=" ")
    print(sum(getsize(join(root, name)) for name in files), end=" ")
    print("bytes in", len(files), "non-directory files")
    if 'CVS' in dirs:
        dirs.remove('CVS')  # don't visit CVS directories

See also

The function returns directory entries along with file attribute information, giving better performance for many common use cases

Changed in version 3. 2. The path parameter became optional.

New in version 3. 3. Added support for specifying path as an open file descriptor.

Changed in version 3. 6. Accepts a .

Thực hiện tương đương với một cuộc gọi hệ thống

os.stat in os.supports_dir_fd

On platforms that do not support symbolic links, this is an alias for

As of Python 3. 3, this is equivalent to

os.stat in os.supports_dir_fd

This function can also support

See also

The function

Changed in version 3. 2. Added support for Windows 6. 0 (Vista) symbolic links.

Changed in version 3. 3. Added the dir_fd parameter.

Changed in version 3. 6. Accepts a .

Changed in version 3. 8. On Windows, now opens reparse points that represent another path (name surrogates), including symbolic links and directory junctions. Other kinds of reparse points are resolved by the operating system as for .

Create a directory named path with numeric mode mode

If the directory already exists, is raised. If a parent directory in the path does not exist, is raised

On some systems, mode is ignored. Where it is used, the current umask value is first masked out. If bits other than the last 9 (i. e. the last 3 digits of the octal representation of the mode) are set, their meaning is platform-dependent. On some platforms, they are ignored and you should call explicitly to set them

This function can also support

It is also possible to create temporary directories; see the module’s function

Raises an

os.stat in os.supports_dir_fd

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()

try:
    fp = open("myfile")
except PermissionError:
    return "some default data"
else:
    with fp:
        return fp.read()