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:mod:`winreg` -- Windows registry access
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=========================================
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:synopsis: Routines and objects for manipulating the Windows registry.
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.. sectionauthor:: Mark Hammond <MarkH@ActiveState.com>
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These functions expose the Windows registry API to Python. Instead of using an
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integer as the registry handle, a :ref:`handle object <handle-object>` is used
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to ensure that the handles are closed correctly, even if the programmer neglects
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to explicitly close them.
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.. _exception-changed:
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.. versionchanged:: 3.3
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Several functions in this module used to raise a
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:exc:`WindowsError`, which is now an alias of :exc:`OSError`.
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This module offers the following functions:
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.. function:: CloseKey(hkey)
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Closes a previously opened registry key. The *hkey* argument specifies a
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previously opened key.
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If *hkey* is not closed using this method (or via :meth:`hkey.Close()
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<PyHKEY.Close>`), it is closed when the *hkey* object is destroyed by
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.. function:: ConnectRegistry(computer_name, key)
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Establishes a connection to a predefined registry handle on another computer,
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and returns a :ref:`handle object <handle-object>`.
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*computer_name* is the name of the remote computer, of the form
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``r"\\computername"``. If ``None``, the local computer is used.
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*key* is the predefined handle to connect to.
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The return value is the handle of the opened key. If the function fails, an
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:exc:`OSError` exception is raised.
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.. versionchanged:: 3.3
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See :ref:`above <exception-changed>`.
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.. function:: CreateKey(key, sub_key)
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Creates or opens the specified key, returning a
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:ref:`handle object <handle-object>`.
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*key* is an already open key, or one of the predefined
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:ref:`HKEY_* constants <hkey-constants>`.
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*sub_key* is a string that names the key this method opens or creates.
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If *key* is one of the predefined keys, *sub_key* may be ``None``. In that
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case, the handle returned is the same key handle passed in to the function.
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If the key already exists, this function opens the existing key.
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The return value is the handle of the opened key. If the function fails, an
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:exc:`OSError` exception is raised.
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.. versionchanged:: 3.3
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See :ref:`above <exception-changed>`.
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.. function:: CreateKeyEx(key, sub_key, reserved=0, access=KEY_WRITE)
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Creates or opens the specified key, returning a
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:ref:`handle object <handle-object>`.
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*key* is an already open key, or one of the predefined
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:ref:`HKEY_* constants <hkey-constants>`.
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*sub_key* is a string that names the key this method opens or creates.
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*reserved* is a reserved integer, and must be zero. The default is zero.
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*access* is an integer that specifies an access mask that describes the desired
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security access for the key. Default is :const:`KEY_WRITE`. See
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:ref:`Access Rights <access-rights>` for other allowed values.
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If *key* is one of the predefined keys, *sub_key* may be ``None``. In that
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case, the handle returned is the same key handle passed in to the function.
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If the key already exists, this function opens the existing key.
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The return value is the handle of the opened key. If the function fails, an
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:exc:`OSError` exception is raised.
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.. versionadded:: 3.2
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.. versionchanged:: 3.3
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See :ref:`above <exception-changed>`.
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.. function:: DeleteKey(key, sub_key)
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Deletes the specified key.
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*key* is an already open key, or one of the predefined
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:ref:`HKEY_* constants <hkey-constants>`.
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*sub_key* is a string that must be a subkey of the key identified by the *key*
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parameter. This value must not be ``None``, and the key may not have subkeys.
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*This method can not delete keys with subkeys.*
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If the method succeeds, the entire key, including all of its values, is removed.
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If the method fails, an :exc:`OSError` exception is raised.
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.. versionchanged:: 3.3
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See :ref:`above <exception-changed>`.
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.. function:: DeleteKeyEx(key, sub_key, access=KEY_WOW64_64KEY, reserved=0)
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Deletes the specified key.
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The :func:`DeleteKeyEx` function is implemented with the RegDeleteKeyEx
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Windows API function, which is specific to 64-bit versions of Windows.
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See the `RegDeleteKeyEx documentation
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<http://msdn.microsoft.com/en-us/library/ms724847%28VS.85%29.aspx>`__.
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*key* is an already open key, or one of the predefined
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:ref:`HKEY_* constants <hkey-constants>`.
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*sub_key* is a string that must be a subkey of the key identified by the
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*key* parameter. This value must not be ``None``, and the key may not have
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*reserved* is a reserved integer, and must be zero. The default is zero.
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*access* is an integer that specifies an access mask that describes the desired
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security access for the key. Default is :const:`KEY_ALL_ACCESS`. See
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:ref:`Access Rights <access-rights>` for other allowed values.
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*This method can not delete keys with subkeys.*
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If the method succeeds, the entire key, including all of its values, is
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removed. If the method fails, an :exc:`OSError` exception is raised.
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On unsupported Windows versions, :exc:`NotImplementedError` is raised.
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.. versionadded:: 3.2
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.. versionchanged:: 3.3
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See :ref:`above <exception-changed>`.
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.. function:: DeleteValue(key, value)
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Removes a named value from a registry key.
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*key* is an already open key, or one of the predefined
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:ref:`HKEY_* constants <hkey-constants>`.
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*value* is a string that identifies the value to remove.
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.. function:: EnumKey(key, index)
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Enumerates subkeys of an open registry key, returning a string.
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*key* is an already open key, or one of the predefined
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:ref:`HKEY_* constants <hkey-constants>`.
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*index* is an integer that identifies the index of the key to retrieve.
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The function retrieves the name of one subkey each time it is called. It is
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typically called repeatedly until an :exc:`OSError` exception is
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raised, indicating, no more values are available.
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.. versionchanged:: 3.3
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See :ref:`above <exception-changed>`.
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.. function:: EnumValue(key, index)
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Enumerates values of an open registry key, returning a tuple.
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*key* is an already open key, or one of the predefined
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:ref:`HKEY_* constants <hkey-constants>`.
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*index* is an integer that identifies the index of the value to retrieve.
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The function retrieves the name of one subkey each time it is called. It is
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typically called repeatedly, until an :exc:`OSError` exception is
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raised, indicating no more values.
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The result is a tuple of 3 items:
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+-------+--------------------------------------------+
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+=======+============================================+
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| ``0`` | A string that identifies the value name |
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+-------+--------------------------------------------+
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| ``1`` | An object that holds the value data, and |
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| | whose type depends on the underlying |
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+-------+--------------------------------------------+
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| ``2`` | An integer that identifies the type of the |
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| | value data (see table in docs for |
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| | :meth:`SetValueEx`) |
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+-------+--------------------------------------------+
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.. versionchanged:: 3.3
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See :ref:`above <exception-changed>`.
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.. function:: ExpandEnvironmentStrings(str)
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Expands environment variable placeholders ``%NAME%`` in strings like
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:const:`REG_EXPAND_SZ`::
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>>> ExpandEnvironmentStrings('%windir%')
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.. function:: FlushKey(key)
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Writes all the attributes of a key to the registry.
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*key* is an already open key, or one of the predefined
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:ref:`HKEY_* constants <hkey-constants>`.
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It is not necessary to call :func:`FlushKey` to change a key. Registry changes are
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flushed to disk by the registry using its lazy flusher. Registry changes are
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also flushed to disk at system shutdown. Unlike :func:`CloseKey`, the
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:func:`FlushKey` method returns only when all the data has been written to the
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registry. An application should only call :func:`FlushKey` if it requires
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absolute certainty that registry changes are on disk.
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If you don't know whether a :func:`FlushKey` call is required, it probably
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.. function:: LoadKey(key, sub_key, file_name)
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Creates a subkey under the specified key and stores registration information
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from a specified file into that subkey.
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*key* is a handle returned by :func:`ConnectRegistry` or one of the constants
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:const:`HKEY_USERS` or :const:`HKEY_LOCAL_MACHINE`.
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*sub_key* is a string that identifies the subkey to load.
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*file_name* is the name of the file to load registry data from. This file must
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have been created with the :func:`SaveKey` function. Under the file allocation
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table (FAT) file system, the filename may not have an extension.
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A call to :func:`LoadKey` fails if the calling process does not have the
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:const:`SE_RESTORE_PRIVILEGE` privilege. Note that privileges are different
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from permissions -- see the `RegLoadKey documentation
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<http://msdn.microsoft.com/en-us/library/ms724889%28v=VS.85%29.aspx>`__ for
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If *key* is a handle returned by :func:`ConnectRegistry`, then the path
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specified in *file_name* is relative to the remote computer.
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.. function:: OpenKey(key, sub_key, reserved=0, access=KEY_READ)
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OpenKeyEx(key, sub_key, reserved=0, access=KEY_READ)
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Opens the specified key, returning a :ref:`handle object <handle-object>`.
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*key* is an already open key, or one of the predefined
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:ref:`HKEY_* constants <hkey-constants>`.
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*sub_key* is a string that identifies the sub_key to open.
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*reserved* is a reserved integer, and must be zero. The default is zero.
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*access* is an integer that specifies an access mask that describes the desired
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security access for the key. Default is :const:`KEY_READ`. See :ref:`Access
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Rights <access-rights>` for other allowed values.
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The result is a new handle to the specified key.
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If the function fails, :exc:`OSError` is raised.
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.. versionchanged:: 3.2
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Allow the use of named arguments.
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.. versionchanged:: 3.3
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See :ref:`above <exception-changed>`.
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.. function:: QueryInfoKey(key)
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Returns information about a key, as a tuple.
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*key* is an already open key, or one of the predefined
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:ref:`HKEY_* constants <hkey-constants>`.
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The result is a tuple of 3 items:
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+-------+---------------------------------------------+
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+=======+=============================================+
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| ``0`` | An integer giving the number of sub keys |
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+-------+---------------------------------------------+
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| ``1`` | An integer giving the number of values this |
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+-------+---------------------------------------------+
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| ``2`` | An integer giving when the key was last |
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| | modified (if available) as 100's of |
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| | nanoseconds since Jan 1, 1600. |
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+-------+---------------------------------------------+
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.. function:: QueryValue(key, sub_key)
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Retrieves the unnamed value for a key, as a string.
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*key* is an already open key, or one of the predefined
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:ref:`HKEY_* constants <hkey-constants>`.
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*sub_key* is a string that holds the name of the subkey with which the value is
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associated. If this parameter is ``None`` or empty, the function retrieves the
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value set by the :func:`SetValue` method for the key identified by *key*.
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Values in the registry have name, type, and data components. This method
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retrieves the data for a key's first value that has a NULL name. But the
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underlying API call doesn't return the type, so always use
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:func:`QueryValueEx` if possible.
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.. function:: QueryValueEx(key, value_name)
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Retrieves the type and data for a specified value name associated with
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an open registry key.
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*key* is an already open key, or one of the predefined
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:ref:`HKEY_* constants <hkey-constants>`.
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*value_name* is a string indicating the value to query.
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The result is a tuple of 2 items:
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+-------+-----------------------------------------+
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+=======+=========================================+
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| ``0`` | The value of the registry item. |
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+-------+-----------------------------------------+
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| ``1`` | An integer giving the registry type for |
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| | this value (see table in docs for |
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| | :meth:`SetValueEx`) |
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+-------+-----------------------------------------+
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.. function:: SaveKey(key, file_name)
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Saves the specified key, and all its subkeys to the specified file.
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*key* is an already open key, or one of the predefined
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:ref:`HKEY_* constants <hkey-constants>`.
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*file_name* is the name of the file to save registry data to. This file
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cannot already exist. If this filename includes an extension, it cannot be
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used on file allocation table (FAT) file systems by the :meth:`LoadKey`
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If *key* represents a key on a remote computer, the path described by
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*file_name* is relative to the remote computer. The caller of this method must
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possess the :const:`SeBackupPrivilege` security privilege. Note that
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privileges are different than permissions -- see the
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`Conflicts Between User Rights and Permissions documentation
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<http://msdn.microsoft.com/en-us/library/ms724878%28v=VS.85%29.aspx>`__
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This function passes NULL for *security_attributes* to the API.
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.. function:: SetValue(key, sub_key, type, value)
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Associates a value with a specified key.
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*key* is an already open key, or one of the predefined
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:ref:`HKEY_* constants <hkey-constants>`.
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*sub_key* is a string that names the subkey with which the value is associated.
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*type* is an integer that specifies the type of the data. Currently this must be
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:const:`REG_SZ`, meaning only strings are supported. Use the :func:`SetValueEx`
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function for support for other data types.
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*value* is a string that specifies the new value.
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If the key specified by the *sub_key* parameter does not exist, the SetValue
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Value lengths are limited by available memory. Long values (more than 2048
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bytes) should be stored as files with the filenames stored in the configuration
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registry. This helps the registry perform efficiently.
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The key identified by the *key* parameter must have been opened with
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:const:`KEY_SET_VALUE` access.
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.. function:: SetValueEx(key, value_name, reserved, type, value)
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Stores data in the value field of an open registry key.
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*key* is an already open key, or one of the predefined
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:ref:`HKEY_* constants <hkey-constants>`.
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*value_name* is a string that names the subkey with which the value is
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*reserved* can be anything -- zero is always passed to the API.
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*type* is an integer that specifies the type of the data. See
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:ref:`Value Types <value-types>` for the available types.
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*value* is a string that specifies the new value.
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This method can also set additional value and type information for the specified
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key. The key identified by the key parameter must have been opened with
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:const:`KEY_SET_VALUE` access.
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To open the key, use the :func:`CreateKey` or :func:`OpenKey` methods.
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Value lengths are limited by available memory. Long values (more than 2048
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bytes) should be stored as files with the filenames stored in the configuration
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registry. This helps the registry perform efficiently.
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.. function:: DisableReflectionKey(key)
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Disables registry reflection for 32-bit processes running on a 64-bit
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*key* is an already open key, or one of the predefined :ref:`HKEY_* constants
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Will generally raise :exc:`NotImplemented` if executed on a 32-bit operating
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If the key is not on the reflection list, the function succeeds but has no
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effect. Disabling reflection for a key does not affect reflection of any
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.. function:: EnableReflectionKey(key)
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Restores registry reflection for the specified disabled key.
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*key* is an already open key, or one of the predefined :ref:`HKEY_* constants
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Will generally raise :exc:`NotImplemented` if executed on a 32-bit operating
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Restoring reflection for a key does not affect reflection of any subkeys.
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.. function:: QueryReflectionKey(key)
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Determines the reflection state for the specified key.
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*key* is an already open key, or one of the predefined
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:ref:`HKEY_* constants <hkey-constants>`.
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Returns ``True`` if reflection is disabled.
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Will generally raise :exc:`NotImplemented` if executed on a 32-bit
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The following constants are defined for use in many :mod:`_winreg` functions.
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.. data:: HKEY_CLASSES_ROOT
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Registry entries subordinate to this key define types (or classes) of
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documents and the properties associated with those types. Shell and
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COM applications use the information stored under this key.
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.. data:: HKEY_CURRENT_USER
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Registry entries subordinate to this key define the preferences of
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the current user. These preferences include the settings of
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environment variables, data about program groups, colors, printers,
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network connections, and application preferences.
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.. data:: HKEY_LOCAL_MACHINE
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Registry entries subordinate to this key define the physical state
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of the computer, including data about the bus type, system memory,
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and installed hardware and software.
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Registry entries subordinate to this key define the default user
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configuration for new users on the local computer and the user
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configuration for the current user.
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.. data:: HKEY_PERFORMANCE_DATA
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Registry entries subordinate to this key allow you to access
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performance data. The data is not actually stored in the registry;
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the registry functions cause the system to collect the data from
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.. data:: HKEY_CURRENT_CONFIG
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Contains information about the current hardware profile of the
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local computer system.
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.. data:: HKEY_DYN_DATA
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This key is not used in versions of Windows after 98.
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For more information, see `Registry Key Security and Access
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<http://msdn.microsoft.com/en-us/library/ms724878%28v=VS.85%29.aspx>`__.
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.. data:: KEY_ALL_ACCESS
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Combines the STANDARD_RIGHTS_REQUIRED, :const:`KEY_QUERY_VALUE`,
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:const:`KEY_SET_VALUE`, :const:`KEY_CREATE_SUB_KEY`,
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:const:`KEY_ENUMERATE_SUB_KEYS`, :const:`KEY_NOTIFY`,
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and :const:`KEY_CREATE_LINK` access rights.
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Combines the STANDARD_RIGHTS_WRITE, :const:`KEY_SET_VALUE`, and
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:const:`KEY_CREATE_SUB_KEY` access rights.
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Combines the STANDARD_RIGHTS_READ, :const:`KEY_QUERY_VALUE`,
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:const:`KEY_ENUMERATE_SUB_KEYS`, and :const:`KEY_NOTIFY` values.
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.. data:: KEY_EXECUTE
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Equivalent to :const:`KEY_READ`.
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.. data:: KEY_QUERY_VALUE
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Required to query the values of a registry key.
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.. data:: KEY_SET_VALUE
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Required to create, delete, or set a registry value.
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.. data:: KEY_CREATE_SUB_KEY
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Required to create a subkey of a registry key.
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.. data:: KEY_ENUMERATE_SUB_KEYS
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Required to enumerate the subkeys of a registry key.
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Required to request change notifications for a registry key or for
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subkeys of a registry key.
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.. data:: KEY_CREATE_LINK
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Reserved for system use.
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.. _64-bit-access-rights:
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For more information, see `Accessing an Alternate Registry View
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<http://msdn.microsoft.com/en-us/library/aa384129(v=VS.85).aspx>`__.
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.. data:: KEY_WOW64_64KEY
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Indicates that an application on 64-bit Windows should operate on
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the 64-bit registry view.
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.. data:: KEY_WOW64_32KEY
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Indicates that an application on 64-bit Windows should operate on
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the 32-bit registry view.
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For more information, see `Registry Value Types
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<http://msdn.microsoft.com/en-us/library/ms724884%28v=VS.85%29.aspx>`__.
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Binary data in any form.
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.. data:: REG_DWORD_LITTLE_ENDIAN
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A 32-bit number in little-endian format.
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.. data:: REG_DWORD_BIG_ENDIAN
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A 32-bit number in big-endian format.
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.. data:: REG_EXPAND_SZ
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Null-terminated string containing references to environment
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variables (``%PATH%``).
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A Unicode symbolic link.
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.. data:: REG_MULTI_SZ
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A sequence of null-terminated strings, terminated by two null characters.
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(Python handles this termination automatically.)
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No defined value type.
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.. data:: REG_RESOURCE_LIST
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A device-driver resource list.
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.. data:: REG_FULL_RESOURCE_DESCRIPTOR
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.. data:: REG_RESOURCE_REQUIREMENTS_LIST
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A hardware resource list.
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A null-terminated string.
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Registry Handle Objects
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-----------------------
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This object wraps a Windows HKEY object, automatically closing it when the
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object is destroyed. To guarantee cleanup, you can call either the
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:meth:`~PyHKEY.Close` method on the object, or the :func:`CloseKey` function.
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All registry functions in this module return one of these objects.
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All registry functions in this module which accept a handle object also accept
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an integer, however, use of the handle object is encouraged.
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Handle objects provide semantics for :meth:`__bool__` -- thus ::
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will print ``Yes`` if the handle is currently valid (has not been closed or
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The object also support comparison semantics, so handle objects will compare
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true if they both reference the same underlying Windows handle value.
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Handle objects can be converted to an integer (e.g., using the built-in
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:func:`int` function), in which case the underlying Windows handle value is
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returned. You can also use the :meth:`~PyHKEY.Detach` method to return the
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integer handle, and also disconnect the Windows handle from the handle object.
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.. method:: PyHKEY.Close()
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Closes the underlying Windows handle.
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If the handle is already closed, no error is raised.
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.. method:: PyHKEY.Detach()
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Detaches the Windows handle from the handle object.
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The result is an integer that holds the value of the handle before it is
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detached. If the handle is already detached or closed, this will return
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After calling this function, the handle is effectively invalidated, but the
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handle is not closed. You would call this function when you need the
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underlying Win32 handle to exist beyond the lifetime of the handle object.
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.. method:: PyHKEY.__enter__()
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PyHKEY.__exit__(\*exc_info)
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The HKEY object implements :meth:`~object.__enter__` and
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:meth:`~object.__exit__` and thus supports the context protocol for the
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:keyword:`with` statement::
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with OpenKey(HKEY_LOCAL_MACHINE, "foo") as key:
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will automatically close *key* when control leaves the :keyword:`with` block.
added
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Doc/library/winreg.rst
