ctypes.WINFUNCTYPE(restype, *argtypes, use_errno=False, use_last_error=False) Windows only: The returned function prototype creates functions that use the stdcall calling convention, except on Windows CE where WINFUNCTYPE() is the same as CFUNCTYPE(). The function will release the GIL during the call. use_errno and use_last_error have the same meaning as above.

ctypes.WinError(code=None, descr=None) Windows only: this function is probably the worst-named thing in ctypes. It creates an instance of OSError. If code is not specified, GetLastError is called to determine the error code. If descr is not specified, FormatError() is called to get a textual description of the error. Changed in version 3.3: An instance of WindowsError used to be created.

class ctypes.WinDLL(name, mode=DEFAULT_MODE, handle=None, use_errno=False, use_last_error=False) Windows only: Instances of this class represent loaded shared libraries, functions in these libraries use the stdcall calling convention, and are assumed to return int by default. On Windows CE only the standard calling convention is used, for convenience the WinDLL and OleDLL use the standard calling convention on this platform.

ctypes.util.find_msvcrt() Windows only: return the filename of the VC runtime library used by Python, and by the extension modules. If the name of the library cannot be determined, None is returned. If you need to free memory, for example, allocated by an extension module with a call to the free(void *), it is important that you use the function in the same library that allocated the memory.

ctypes.util.find_library(name) Try to find a library and return a pathname. name is the library name without any prefix like lib, suffix like .so, .dylib or version number (this is the form used for the posix linker option -l). If no library can be found, returns None. The exact functionality is system dependent.

class ctypes.Union(*args, **kw) Abstract base class for unions in native byte order.

_pack_ An optional small integer that allows overriding the alignment of structure fields in the instance. _pack_ must already be defined when _fields_ is assigned, otherwise it will have no effect.

_fields_ A sequence defining the structure fields. The items must be 2-tuples or 3-tuples. The first item is the name of the field, the second item specifies the type of the field; it can be any ctypes data type. For integer type fields like c_int, a third optional item can be given. It must be a small positive integer defining the bit width of the field. Field names must be unique within one structure or union. This is not checked, only one field can be accessed when names are repeated. It

_anonymous_ An optional sequence that lists the names of unnamed (anonymous) fields. _anonymous_ must be already defined when _fields_ is assigned, otherwise it will have no effect. The fields listed in this variable must be structure or union type fields. ctypes will create descriptors in the structure type that allows accessing the nested fields directly, without the need to create the structure or union field. Here is an example type (Windows): class _U(Union): _fields_ = [("lptdesc",

class ctypes.Structure(*args, **kw) Abstract base class for structures in native byte order. Concrete structure and union types must be created by subclassing one of these types, and at least define a _fields_ class variable. ctypes will create descriptors which allow reading and writing the fields by direct attribute accesses. These are the _fields_ A sequence defining the structure fields. The items must be 2-tuples or 3-tuples. The first item is the name of the field, the second item s