34.3. _winreg – Windows registry access
Note
The _winreg module has been renamed to winreg in Python 3.0.
The 2to3 tool will automatically adapt imports when converting your
sources to 3.0.
New in version 2.0:
New in version 2.0.
These functions expose the Windows registry API to Python. Instead of using an
integer as the registry handle, a handle object is used
to ensure that the handles are closed correctly, even if the programmer neglects
to explicitly close them.
This module offers the following functions:
-
_winreg.CloseKey(hkey)
Closes a previously opened registry key. The hkey argument specifies a
previously opened key.
Note
If hkey is not closed using this method (or via hkey.Close()),
it is closed when the hkey object is destroyed by Python.
-
_winreg.ConnectRegistry(computer_name, key)
Establishes a connection to a predefined registry handle on another computer,
and returns a handle object.
computer_name is the name of the remote computer, of the form
r"\\computername". If None, the local computer is used.
key is the predefined handle to connect to.
The return value is the handle of the opened key. If the function fails, a
WindowsError exception is raised.
-
_winreg.CreateKey(key, sub_key)
Creates or opens the specified key, returning a
handle object.
key is an already open key, or one of the predefined
HKEY_* constants.
sub_key is a string that names the key this method opens or creates.
If key is one of the predefined keys, sub_key may be None. In that
case, the handle returned is the same key handle passed in to the function.
If the key already exists, this function opens the existing key.
The return value is the handle of the opened key. If the function fails, a
WindowsError exception is raised.
-
_winreg.DeleteKey(key, sub_key)
Deletes the specified key.
key is an already open key, or any one of the predefined
HKEY_* constants.
sub_key is a string that must be a subkey of the key identified by the key
parameter. This value must not be None, and the key may not have subkeys.
This method can not delete keys with subkeys.
If the method succeeds, the entire key, including all of its values, is removed.
If the method fails, a WindowsError exception is raised.
-
_winreg.DeleteValue(key, value)
Removes a named value from a registry key.
key is an already open key, or one of the predefined
HKEY_* constants.
value is a string that identifies the value to remove.
-
_winreg.EnumKey(key, index)
Enumerates subkeys of an open registry key, returning a string.
key is an already open key, or any one of the predefined
HKEY_* constants.
index is an integer that identifies the index of the key to retrieve.
The function retrieves the name of one subkey each time it is called. It is
typically called repeatedly until a WindowsError exception is
raised, indicating, no more values are available.
-
_winreg.EnumValue(key, index)
Enumerates values of an open registry key, returning a tuple.
key is an already open key, or any one of the predefined
HKEY_* constants.
index is an integer that identifies the index of the value to retrieve.
The function retrieves the name of one subkey each time it is called. It is
typically called repeatedly, until a WindowsError exception is
raised, indicating no more values.
The result is a tuple of 3 items:
| Index |
Meaning |
|---|
0 |
A string that identifies the value name |
1 |
An object that holds the value data, and
whose type depends on the underlying
registry type |
2 |
An integer that identifies the type of the
value data (see table in docs for
SetValueEx()) |
-
_winreg.ExpandEnvironmentStrings(unicode)
Expands environment variable placeholders %NAME% in unicode strings like
REG_EXPAND_SZ:
>>> ExpandEnvironmentStrings(u"%windir%")
u"C:\\Windows"
New in version 2.6:
New in version 2.6.
-
_winreg.FlushKey(key)
Writes all the attributes of a key to the registry.
key is an already open key, or one of the predefined
HKEY_* constants.
It is not necessary to call FlushKey() to change a key. Registry changes are
flushed to disk by the registry using its lazy flusher. Registry changes are
also flushed to disk at system shutdown. Unlike CloseKey(), the
FlushKey() method returns only when all the data has been written to the
registry. An application should only call FlushKey() if it requires
absolute certainty that registry changes are on disk.
Note
If you don’t know whether a FlushKey() call is required, it probably
isn’t.
-
_winreg.LoadKey(key, sub_key, file_name)
Creates a subkey under the specified key and stores registration information
from a specified file into that subkey.
key is a handle returned by ConnectRegistry() or one of the constants
HKEY_USERS or HKEY_LOCAL_MACHINE.
sub_key is a string that identifies the subkey to load.
file_name is the name of the file to load registry data from. This file must
have been created with the SaveKey() function. Under the file allocation
table (FAT) file system, the filename may not have an extension.
A call to LoadKey() fails if the calling process does not have the
SE_RESTORE_PRIVILEGE privilege. Note that privileges are different
from permissions – see the RegLoadKey documentation for
more details.
If key is a handle returned by ConnectRegistry(), then the path
specified in file_name is relative to the remote computer.
-
_winreg.OpenKey(key, sub_key[, res[, sam]])
Opens the specified key, returning a handle object.
key is an already open key, or any one of the predefined
HKEY_* constants.
sub_key is a string that identifies the sub_key to open.
res is a reserved integer, and must be zero. The default is zero.
sam is an integer that specifies an access mask that describes the desired
security access for the key. Default is KEY_READ. See
Access Rights for other allowed values.
The result is a new handle to the specified key.
If the function fails, WindowsError is raised.
-
_winreg.OpenKeyEx()
The functionality of OpenKeyEx() is provided via OpenKey(),
by the use of default arguments.
-
_winreg.QueryInfoKey(key)
Returns information about a key, as a tuple.
key is an already open key, or one of the predefined
HKEY_* constants.
The result is a tuple of 3 items:
| Index |
Meaning |
|---|
0 |
An integer giving the number of sub keys
this key has. |
1 |
An integer giving the number of values this
key has. |
2 |
A long integer giving when the key was last
modified (if available) as 100’s of
nanoseconds since Jan 1, 1600. |
-
_winreg.QueryValue(key, sub_key)
Retrieves the unnamed value for a key, as a string.
key is an already open key, or one of the predefined
HKEY_* constants.
sub_key is a string that holds the name of the subkey with which the value is
associated. If this parameter is None or empty, the function retrieves the
value set by the SetValue() method for the key identified by key.
Values in the registry have name, type, and data components. This method
retrieves the data for a key’s first value that has a NULL name. But the
underlying API call doesn’t return the type, so always use
QueryValueEx() if possible.
-
_winreg.QueryValueEx(key, value_name)
Retrieves the type and data for a specified value name associated with
an open registry key.
key is an already open key, or one of the predefined
HKEY_* constants.
value_name is a string indicating the value to query.
The result is a tuple of 2 items:
| Index |
Meaning |
|---|
0 |
The value of the registry item. |
1 |
An integer giving the registry type for
this value (see table in docs for
SetValueEx()) |
-
_winreg.SaveKey(key, file_name)
Saves the specified key, and all its subkeys to the specified file.
key is an already open key, or one of the predefined
HKEY_* constants.
file_name is the name of the file to save registry data to. This file
cannot already exist. If this filename includes an extension, it cannot be
used on file allocation table (FAT) file systems by the LoadKey()
method.
If key represents a key on a remote computer, the path described by
file_name is relative to the remote computer. The caller of this method must
possess the SeBackupPrivilege security privilege. Note that
privileges are different than permissions – see the
Conflicts Between User Rights and Permissions documentation
for more details.
This function passes NULL for security_attributes to the API.
-
_winreg.SetValue(key, sub_key, type, value)
Associates a value with a specified key.
key is an already open key, or one of the predefined
HKEY_* constants.
sub_key is a string that names the subkey with which the value is associated.
type is an integer that specifies the type of the data. Currently this must be
REG_SZ, meaning only strings are supported. Use the SetValueEx()
function for support for other data types.
value is a string that specifies the new value.
If the key specified by the sub_key parameter does not exist, the SetValue
function creates it.
Value lengths are limited by available memory. Long values (more than 2048
bytes) should be stored as files with the filenames stored in the configuration
registry. This helps the registry perform efficiently.
The key identified by the key parameter must have been opened with
KEY_SET_VALUE access.
-
_winreg.SetValueEx(key, value_name, reserved, type, value)
Stores data in the value field of an open registry key.
key is an already open key, or one of the predefined
HKEY_* constants.
value_name is a string that names the subkey with which the value is
associated.
type is an integer that specifies the type of the data. See
Value Types for the available types.
reserved can be anything – zero is always passed to the API.
value is a string that specifies the new value.
This method can also set additional value and type information for the specified
key. The key identified by the key parameter must have been opened with
KEY_SET_VALUE access.
To open the key, use the CreateKey() or OpenKey() methods.
Value lengths are limited by available memory. Long values (more than 2048
bytes) should be stored as files with the filenames stored in the configuration
registry. This helps the registry perform efficiently.
-
_winreg.DisableReflectionKey(key)
Disables registry reflection for 32-bit processes running on a 64-bit
operating system.
key is an already open key, or one of the predefined
HKEY_* constants.
Will generally raise NotImplemented if executed on a 32-bit
operating system.
If the key is not on the reflection list, the function succeeds but has no
effect. Disabling reflection for a key does not affect reflection of any
subkeys.
-
_winreg.EnableReflectionKey(key)
Restores registry reflection for the specified disabled key.
key is an already open key, or one of the predefined
HKEY_* constants.
Will generally raise NotImplemented if executed on a 32-bit
operating system.
Restoring reflection for a key does not affect reflection of any subkeys.
-
_winreg.QueryReflectionKey(key)
Determines the reflection state for the specified key.
key is an already open key, or one of the predefined
HKEY_* constants.
Returns True if reflection is disabled.
Will generally raise NotImplemented if executed on a 32-bit
operating system.
34.3.1. Constants
The following constants are defined for use in many _winreg functions.
34.3.1.1. HKEY_* Constants
-
_winreg.HKEY_CLASSES_ROOT
Registry entries subordinate to this key define types (or classes) of
documents and the properties associated with those types. Shell and
COM applications use the information stored under this key.
-
_winreg.HKEY_CURRENT_USER
Registry entries subordinate to this key define the preferences of
the current user. These preferences include the settings of
environment variables, data about program groups, colors, printers,
network connections, and application preferences.
-
_winreg.HKEY_LOCAL_MACHINE
Registry entries subordinate to this key define the physical state
of the computer, including data about the bus type, system memory,
and installed hardware and software.
-
_winreg.HKEY_USERS
Registry entries subordinate to this key define the default user
configuration for new users on the local computer and the user
configuration for the current user.
-
_winreg.HKEY_PERFORMANCE_DATA
Registry entries subordinate to this key allow you to access
performance data. The data is not actually stored in the registry;
the registry functions cause the system to collect the data from
its source.
-
_winreg.HKEY_CURRENT_CONFIG
Contains information about the current hardware profile of the
local computer system.
-
_winreg.HKEY_DYN_DATA
This key is not used in versions of Windows after 98.
34.3.1.2. Access Rights
For more information, see Registry Key Security and Access.
-
_winreg.KEY_ALL_ACCESS
Combines the STANDARD_RIGHTS_REQUIRED, KEY_QUERY_VALUE,
KEY_SET_VALUE, KEY_CREATE_SUB_KEY,
KEY_ENUMERATE_SUB_KEYS, KEY_NOTIFY,
and KEY_CREATE_LINK access rights.
-
_winreg.KEY_WRITE
Combines the STANDARD_RIGHTS_WRITE, KEY_SET_VALUE, and
KEY_CREATE_SUB_KEY access rights.
-
_winreg.KEY_READ
Combines the STANDARD_RIGHTS_READ, KEY_QUERY_VALUE,
KEY_ENUMERATE_SUB_KEYS, and KEY_NOTIFY values.
-
_winreg.KEY_EXECUTE
Equivalent to KEY_READ.
-
_winreg.KEY_QUERY_VALUE
Required to query the values of a registry key.
-
_winreg.KEY_SET_VALUE
Required to create, delete, or set a registry value.
-
_winreg.KEY_CREATE_SUB_KEY
Required to create a subkey of a registry key.
-
_winreg.KEY_ENUMERATE_SUB_KEYS
Required to enumerate the subkeys of a registry key.
-
_winreg.KEY_NOTIFY
Required to request change notifications for a registry key or for
subkeys of a registry key.
-
_winreg.KEY_CREATE_LINK
Reserved for system use.
34.3.1.2.1. 64-bit Specific
For more information, see Accesing an Alternate Registry View.
-
_winreg.KEY_WOW64_64KEY
Indicates that an application on 64-bit Windows should operate on
the 64-bit registry view.
-
_winreg.KEY_WOW64_32KEY
Indicates that an application on 64-bit Windows should operate on
the 32-bit registry view.
34.3.1.3. Value Types
For more information, see Registry Value Types.
-
_winreg.REG_BINARY
Binary data in any form.
-
_winreg.REG_DWORD
32-bit number.
-
_winreg.REG_DWORD_LITTLE_ENDIAN
A 32-bit number in little-endian format.
-
_winreg.REG_DWORD_BIG_ENDIAN
A 32-bit number in big-endian format.
-
_winreg.REG_EXPAND_SZ
Null-terminated string containing references to environment
variables (%PATH%).
-
_winreg.REG_LINK
A Unicode symbolic link.
-
_winreg.REG_MULTI_SZ
A sequence of null-terminated strings, terminated by two null characters.
(Python handles this termination automatically.)
-
_winreg.REG_NONE
No defined value type.
-
_winreg.REG_RESOURCE_LIST
A device-driver resource list.
-
_winreg.REG_FULL_RESOURCE_DESCRIPTOR
A hardware setting.
-
_winreg.REG_RESOURCE_REQUIREMENTS_LIST
A hardware resource list.
-
_winreg.REG_SZ
A null-terminated string.
34.3.2. Registry Handle Objects
This object wraps a Windows HKEY object, automatically closing it when the
object is destroyed. To guarantee cleanup, you can call either the
Close() method on the object, or the CloseKey() function.
All registry functions in this module return one of these objects.
All registry functions in this module which accept a handle object also accept
an integer, however, use of the handle object is encouraged.
Handle objects provide semantics for __nonzero__() – thus:
will print Yes if the handle is currently valid (has not been closed or
detached).
The object also support comparison semantics, so handle objects will compare
true if they both reference the same underlying Windows handle value.
Handle objects can be converted to an integer (e.g., using the built-in
int() function), in which case the underlying Windows handle value is
returned. You can also use the Detach() method to return the
integer handle, and also disconnect the Windows handle from the handle object.
-
PyHKEY.Close()
Closes the underlying Windows handle.
If the handle is already closed, no error is raised.
-
PyHKEY.Detach()
Detaches the Windows handle from the handle object.
The result is an integer (or long on 64 bit Windows) that holds the value of the
handle before it is detached. If the handle is already detached or closed, this
will return zero.
After calling this function, the handle is effectively invalidated, but the
handle is not closed. You would call this function when you need the
underlying Win32 handle to exist beyond the lifetime of the handle object.
-
PyHKEY.__enter__()
-
PyHKEY.__exit__(*exc_info)
The HKEY object implements __enter__() and
__exit__() and thus supports the context protocol for the
with statement:
with OpenKey(HKEY_LOCAL_MACHINE, "foo") as key:
... # work with key
will automatically close key when control leaves the with block.
New in version 2.6:
New in version 2.6.