14.14.2.7 Fundamental data types

###
14.14.2.7 Fundamental data types

class `_SimpleCData`
  This non-public class is the base class of all fundamental ctypes data types. It is mentioned here because it contains the common attributes of the fundamental ctypes data types. `_SimpleCData` is a subclass of `_CData`, so it inherits their methods and attributes.

Instances have a single attribute:

`value`
  This attribute contains the actual value of the instance. For integer and pointer types, it is an integer, for character types, it is a single character string, for character pointer types it is a Python string or unicode string.

  When the `value` attribute is retrieved from a ctypes instance, usually a new object is returned each time. `ctypes` does not implement original object return, always a new object is constructed. The same is true for all other ctypes object instances.

Fundamental data types, when returned as foreign function call results, or, for example, by retrieving structure field members or array items, are transparently converted to native Python types. In other words, if a foreign function has a `restype` of `c_char_p`, you will always receive a Python string, not a `c_char_p` instance.

Subclasses of fundamental data types do not inherit this behaviour. So, if a foreign functions `restype` is a subclass of `c_void_p`, you will receive an instance of this subclass from the function call. Of course, you can get the value of the pointer by accessing the `value` attribute.

These are the fundamental ctypes data types:

class `c_byte`
  Represents the C signed char datatype, and interprets the value as small integer. The constructor accepts an optional integer initializer; no overflow checking is done.

class `c_char`
  Represents the C char datatype, and interprets the value as a single character. The constructor accepts an optional string initializer, the length of the string must be exactly one character.

class `c_char_p`
  Represents the C char * datatype, which must be a pointer to a zero-terminated string. The constructor accepts an integer address, or a string.

class `c_double`
  Represents the C double datatype. The constructor accepts an optional float initializer.

class `c_float`
  Represents the C float datatype. The constructor accepts an optional float initializer.

class `c_int`
  Represents the C signed int datatype. The constructor accepts an optional integer initializer; no overflow checking is done. On platforms where `sizeof(int) == sizeof(long)` it is an alias to `c_long`.

class `c_int8`
  Represents the C 8-bit `signed int` datatype. Usually an alias for `c_byte`.

class `c_int16`
  Represents the C 16-bit signed int datatype. Usually an alias for `c_short`.

class `c_int32`
  Represents the C 32-bit signed int datatype. Usually an alias for `c_int`.

class `c_int64`
  Represents the C 64-bit `signed int` datatype. Usually an alias for `c_longlong`.

class `c_long`
  Represents the C `signed long` datatype. The constructor accepts an optional integer initializer; no overflow checking is done.

class `c_longlong`
  Represents the C `signed long long` datatype. The constructor accepts an optional integer initializer; no overflow checking is done.

class `c_short`
  Represents the C `signed short` datatype. The constructor accepts an optional integer initializer; no overflow checking is done.

class `c_size_t`
  Represents the C `size_t` datatype.

class `c_ubyte`
  Represents the C `unsigned char` datatype, it interprets the value as small integer. The constructor accepts an optional integer initializer; no overflow checking is done.

class `c_uint`
  Represents the C `unsigned int` datatype. The constructor accepts an optional integer initializer; no overflow checking is done. On platforms where `sizeof(int) == sizeof(long)` it is an alias for `c_ulong`.

class `c_uint8`
  Represents the C 8-bit unsigned int datatype. Usually an alias for `c_ubyte`.

class `c_uint16`
  Represents the C 16-bit unsigned int datatype. Usually an alias for `c_ushort`.

class `c_uint32`
  Represents the C 32-bit unsigned int datatype. Usually an alias for `c_uint`.

class `c_uint64`
  Represents the C 64-bit unsigned int datatype. Usually an alias for `c_ulonglong`.

class `c_ulong`
  Represents the C `unsigned long` datatype. The constructor accepts an optional integer initializer; no overflow checking is done.

class `c_ulonglong`
  Represents the C `unsigned long long` datatype. The constructor accepts an optional integer initializer; no overflow checking is done.

class `c_ushort`
  Represents the C `unsigned short` datatype. The constructor accepts an optional integer initializer; no overflow checking is done.

class `c_void_p`
  Represents the C `void *` type. The value is represented as integer. The constructor accepts an optional integer initializer.

class `c_wchar`
  Represents the C `wchar_t` datatype, and interprets the value as a single character unicode string. The constructor accepts an optional string initializer, the length of the string must be exactly one character.

class `c_wchar_p`
  Represents the C `wchar_t *` datatype, which must be a pointer to a zero-terminated wide character string. The constructor accepts an integer address, or a string.

class `HRESULT`
  Windows only: Represents a `HRESULT` value, which contains success or error information for a function or method call.

class `py_object`
  Represents the C `PyObject *` datatype. Calling this without an argument creates a `NULL` `PyObject *` pointer.

The `ctypes.wintypes` module provides quite some other Windows specific data types, for example `HWND`, `WPARAM`, or `DWORD`. Some useful structures like `MSG` or `RECT` are also defined.